Patent Publication Number: US-2006007113-A1

Title: Display apparatus and scanning unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      The present application claims priority to and the benefit of Korean Patent Application No. 2004-52827, filed on Jul. 8, 2004, the disclosure of which is hereby incorporated herein by reference in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a display apparatus and a scanning unit associated therewith. More particularly, the present invention relates to a display apparatus and associated scanning unit capable of increasing scanning speed to improve image display quality.  
      2. Description of the Related Art  
      A conventional rear-projection display apparatus may use a laser beam to generate one or more light patterns that are transmitted to a screen via a scanning unit positioned behind the screen. The transmitted light pattern(s) display a visible image for a viewer positioned on the opposite side of the screen.  
      Typically, one or more light patterns are scanned in a horizontal fashion from one side of the screen to another, by moving from a start point adjacent one side of the screen to an end point adjacent an opposite side of the screen. This movement causes the one or more light patterns to be scanned across the screen from the start point to the end point. The one or more light patterns are then scanned across the screen from a next start point to a next end point. The time required to move the scanning unit from the start point to the end point or from the next start point to the next end point is called a scanning time period. The time required to move the scanning part from the end point to the next start point is called a recovery time period. A loss of the laser beam decreases when a ratio of the scanning time period to the recovery time period is about five to ten.  
      To reduce the scanning time period and the recovery time period, conventional approaches have decreased the size of the screen. When the scanning time period and the recovery time period decrease, however, the ratio of the scanning time period to the recovery time period also decreases so that the loss of the laser beam increases. In addition, the scanning time period may overlap the recovery time period in a unit frame so that a net scanning time period decreases.  
     SUMMARY OF THE INVENTION  
      The present invention provides a display apparatus and a scanning unit capable of increasing scanning speed to improve an image display quality.  
      A display apparatus manufactured according to the principles of the present invention may include a display unit, a scanning unit, a light generating part, and a scanning part. The display unit displays an image. The scanning unit includes a light generating part and a scanning part, and irradiates a laser beam having image information to the display unit. The light generating part generates and emits the laser beam. The scanning part includes at least two scanning mirrors that are transported between upper and lower portions of the display unit to irradiate the laser beam to the display unit.  
      A scanning unit manufactured according to the principles of the present invention may include a first scanning mirror and a second scanning mirror. During a first frame, the first scanning mirror is transported in a first direction to irradiate a laser beam to a subject. During a second frame that follows the first, the first scanning mirror is transported in a second direction that is opposite to the first direction. During the first frame, the second scanning mirror is transported in the second direction. During the second frame, the second scanning mirror is transported in the first direction to irradiate the laser beam to the subject.  
      A scanning unit manufactured according to the principles of the present invention may include a scanning mirror and a lifting part. The scanning mirror irradiates an external light to a subject. The lifting part may move the scanning mirror in a direction substantially perpendicular to a surface of the subject so that the light reflected by an angled surface of the scanning mirror is irradiated to the subject along a first direction.  
      The scanning unit alternately irradiates the laser beam to the display unit during the frames. That is, one of the first and second scanning mirrors irradiates the laser beam to the display unit while another of the first and second scanning mirrors is recovered so that the recovery time period is omitted, thereby increasing a scanning speed of the scanning unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings.  
       FIG. 1  is a perspective view showing a display apparatus in accordance with an exemplary embodiment of the present invention.  
       FIG. 2  is a cross-sectional view taken along a line I-I′ shown in  FIG. 1 .  
       FIG. 3  is a plan view showing a light generating part and a light reflecting part shown in  FIG. 1 .  
       FIG. 4  is a plan view showing a light generating part and a light reflecting part of a display apparatus in accordance with another exemplary embodiment of the present invention.  
       FIG. 5  is a plan view showing a light generating part and a light reflecting part of a display apparatus in accordance with another exemplary embodiment of the present invention.  
       FIG. 6  is a cross-sectional view showing a display apparatus having the light generating part and the light reflecting part shown in  FIG. 5 .  
       FIG. 7  is a cross-sectional view showing a display apparatus in accordance with another exemplary embodiment of the present invention.  
       FIG. 8  is an enlarged cross-sectional view showing a portion  11  shown in  FIG. 7 . 
    
    
     DESCRIPTION OF THE EMBODIMENTS  
      It should be understood that the exemplary embodiments of the present invention described below may be varied modified in many different ways without departing from the inventive principles disclosed herein, and the scope of the present invention is therefore not limited to these particular following embodiments. Rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the concept of the invention to those skilled in the art by way of example and not of limitation.  
      Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.  
       FIG. 1  is a perspective view showing a display apparatus in accordance with an exemplary embodiment of the present invention.  FIG. 2  is a cross-sectional view taken along a line I-I′ shown in  FIG. 1 .  
      Referring to  FIGS. 1 and 2 , the display apparatus  500  may include several main components, a display unit  100 , a light generating unit  200 , a light modulator  220 , a light reflecting part  300 , and a scanning unit  560 . Some or all of these components may be fully or partially enclosed within a cabinet or a frame. For ease of illustration and clarity, neither the cabinet nor the frame are shown in  FIGS. 1 and 2 .  
      The display unit  100  may have a front surface viewable by a user of the display apparatus  500  and back surface on a side opposite the front surface. The scanning unit  560  is positioned behind the display unit&#39;s back surface.  
      The display unit  100  may include a rear projection screen that either focuses or diffuses light shining on a back surface thereof to distribute a bright, crisp image into a predefined viewing zone that extends outwardly from the display unit&#39;s front surface. The screen may have any thickness, curvature, or size suitable for displaying images having an aspect ratio suitable for widescreen television viewing, standard television viewing, or personal computer viewing.  
      The scanning unit  560  includes a light generating part  200 , a light reflecting part  300 , and a scanning part  400 . The scanning unit  560  is located in relation to the light generating part  200  and the display unit  100  such that the scanning unit  560  transfers light emitted from the light generating source  200  onto the display unit&#39;s back surface. In  FIGS. 1 and 2 , the scanning unit  560  is illustratively shown positioned between the light generating part  200  and the display unit  100 , but other configurations are possible. In operation, the light generating part  200  may generate and emit the laser beam onto sequential points of the light reflecting part  300 , which reflects the laser beam towards the scanning part  400 . Components of the scanning unit  560  are transported between upper and lower portions EP 1  and EP 2  of the display unit  100  to irradiate the laser beam from the light reflecting part  300  to the back surface of the display unit  100 . Each of these components is discussed in more detail below.  
      Referring again to  FIGS. 1 and 2 , the scanning part  400  includes a first scanning mirror  410 , a second scanning mirror  420 , a first roller  430 , a second roller  440 , and a band  450 .  
      Roller  430  is positioned a pre-determined distance behind an upper portion EP 1  of the display unit&#39;s back surface. Roller  440  is positioned about an equal pre-determined distance behind a lower portion EP 2  of the display unit&#39;s back surface. Additionally, the first roller  430  is positioned to be spaced apart from and substantially parallel the second roller  440 . The width of each roller  430 ,  440  may approximately equal a width of the display unit&#39;s back surface.  
      The band  450  may be formed of a flexible material and positioned to encircle both rollers  430 ,  440 , and the band&#39;s width may approximately equal the width of either of the rollers  430 ,  440 . In the embodiment of  FIGS. 1 and 2 , the rear surface of the band  450  moves upward from the second roller  440  towards the first roller  430 . This upward direction of movement is depicted as D 1 . Simultaneously, the front surface of the band  450  moves downward from the first roller  430  toward the second roller  440 . This downward direction of movement is designated as D 2 . Of course, in other embodiments, the direction of rotation may be reversed.  
      A first scanning mirror  410  and a second scanning mirror  420  may be coupled to the exterior surface of the band  450  to rotate as the band 45° rotates. A distance between the first and second scanning mirrors  410 ,  420  is about half a total length L (e.g., circumference) of the band  450 . As shown in  FIG. 1 , a width of each scanning mirror  410 ,  420  may approximately equal a width of the band  450 .  
      Referring to  FIG. 2 , each scanning mirror  410 ,  420  may have a cross-section shaped in the form of a right triangle. A base of each scanning mirror  410 ,  420  is coupled to the band  450  such that an angled surface of each scanning mirror  410 ,  420  faces towards the direction of travel.  
      As shown in  FIGS. 1 and 2 , a light reflecting part  300  may be positioned beneath and/or slightly in front of the longitudinal axis of the second roller  440  to reflect light emitted from the light generating unit  200  to at least one of the scanning mirrors  410 ,  420 . Of course, in other embodiments, the light reflecting part  300  may be positioned differently, provided the facing direction of each scanning mirror  410 ,  420  and/or the rotational direction of the band  450  is/are adjusted accordingly.  
      The light generating unit  200  may include a light modulator  220  and a light source  210 . The light modulator may be positioned above the light-reflecting part  300  and in the path of a laser beam emitted from the light source  210 .  
      In use, the light source  210  activates in response from signals received from a controller and emits a laser beam containing image information. The emitted laser beam reflects from the light modulator  220  to the light reflecting part  300 , which reflects the laser beam substantially parallel the front surface of the band  450 . The band 45° rotates at a velocity that moves the scanning mirror  410  or  420  from the top portion EP 1  of the display unit&#39;s back surface to the bottom portion EP 2  of the display unit&#39;s back surface in about 1/60 th  of a second. During this first frame, the first scanning mirror  410  moves in a first direction D 1  from a position parallel the upper portion EP 1  of the display unit  100  to a position parallel the lower portion EP 2  of the display unit  100 . As the scanning mirror  410  moves, it irradiates the laser beam to the display unit  100 .  
      At the same time, the second scanning mirror  420  moves in a second direction D 2  from a position adjacent the lower portion EP 2  of the display unit  100  to a position adjacent the upper portion EP 1  of the display unit  100 . The second direction D 2  is opposite the first direction D 1 . Therefore, the laser beam is not irradiated to the second scanning mirror  420  during the first frame. After the second mirror  420  moves to the upper portion EP 1  of the display unit  100 , the second mirror  420  then moves in the first direction D 1  to irradiate the laser beam to the display unit  100  during a second frame. In this manner, an image is projected onto the display unit&#39;s back surface about sixty times per second.  
      The first and second scanning mirrors  410  and  420  are in scanning states when the first and second scanning mirrors  410  and  420  irradiate the laser beams to the display unit  100 , respectively. The first and second scanning mirrors  410  and  420  are in recovery states when the first and second scanning mirrors  410  and  420  do not irradiate the laser beams to the display unit  100 , respectively.  
      As mentioned above, the first and second scanning mirrors  410  and  420  are inclined with respect to the display unit  100  so that a front surface of each of the first and second scanning mirrors  410  and  420  forms a predetermined angle with respect to the display unit  100 . Therefore, the laser beam that is reflected from the first or second scanning mirror  410  or  420  is incident towards the display unit  100  at an incident angle of about 90°. A velocity of each of the first and second scanning mirrors  410  and  420  may change depending on a size of the display unit  100 . That is, when the size of the display unit  100  increases, the velocity of each of the first and second scanning mirrors  410  and  420  increases. However, when the size of the display unit  100  decreases, the velocity of each of the first and second scanning mirrors  410  and  420  decreases.  
       FIG. 3  is a plan view showing a light generating part and a light reflecting part shown in  FIG. 1 . Referring to  FIGS. 1 and 3 , the light generating part  200  includes a light source  210  and a light modulator  220 . The light source  210  generates mono-colored laser beam portions having red, green and blue wavelengths. The mono-colored laser beam portions from the light source  210  are reflected from the light modulator  220  so that the reflected light from the light modulator  220  passes to the light reflecting part  300 .  
      The light source  210  includes a red laser diode  211 , a green laser diode  212  and a blue laser diode  213 . The red laser diode  211  generates a red laser beam portion RL having a red wavelength based on a red control signal RC that is from a controlling part  550 . The green laser diode  212  generates a green laser beam portion GL having a green wavelength based on a green control signal GC that is from the controlling part  550 . The blue laser diode  213  generates a blue laser beam portion BL having a blue wavelength based on the blue control signal BC that is from the controlling part  550 . Intensities of the red, green and blue laser beam portions RL, GL and BL are determined by the red control signal RC, the green control signal GC, and the blue control signal BC, respectively.  
      The light source  210  further includes a light mixing part  215 . The light mixing part  215  mixes the red, green and blue laser beam portions RL, GL and BL into a laser beam CL. The laser beam CL is irradiated to the light modulator  220 .  
      In this exemplary embodiment, the light modulator  220  is a vibration mirror. Alternatively, the light modulator  220  may be a polygonal rotation mirror. The vibration mirror is inclined at a predetermined angle with respect to the laser beam CL. When the vibration mirror vibrates, an incident angle of the laser beam CL that impinges the vibration mirror changes. When the incident angle of the laser beam CL changes, an exit angle of the laser beam CL also changes. That is, the laser beam CL is reflected from one sequential adjacent position to another as the vibration mirror changes position.  
      In this exemplary embodiment, the light reflecting part  300  is a concave mirror. The laser beam CL reflected from the light modulator  220  may be sequentially irradiated to different positions of the concave mirror. For example, as the light modulator  220  rotates, the laser beam CL from the vibration mirror may move from a first end portion of the concave mirror to a second opposite end portion of the concave mirror.  
      Thereafter, the laser beam CL sequentially reflects from each portion of the light reflecting part  300  to a corresponding sequential portions of the first or second scanning mirror  410  or  420 . From the first or second scanning mirror  410  or  420 , the sequentially reflected laser beam CL is irradiated to the back surface of the display unit  100 .  
       FIG. 4  is a plan view showing a light generating part and a light reflecting part of a display apparatus of another embodiment of the present invention. The display apparatus of  FIG. 4  is same as in FIGS.  1  to  3  except that this embodiment does not include a light generating part or a light reflecting part. Thus, the same reference numerals will be used to refer to the same or like parts as those described in FIGS.  1  to  3  and any further explanation concerning the above elements will be omitted.  
      Referring to  FIGS. 1 and 4 , the light generating part  200  includes a light source  210 ′ that generates mono-colored laser beam portions having red, green and blue wavelengths.  
      The light source  210 ′ includes a red laser diode  211 , a green laser diode  212  and a blue laser diode  213 . The red laser diode  211  generates a red laser beam portion RL having a red wavelength based on a red control signal RC that is from a controlling part  550 . The green laser diode  212  generates a green laser beam portion GL having a green wavelength based on a green control signal GC that is from the controlling part  550 . The blue laser diode  213  generates a blue laser beam portion BL having a blue wavelength based on the blue control signal BC that is from the controlling part  550 . Intensities of the red, green and blue laser beam portions RL, GL and BL are determined by the red control signal RC, the green control signal GC and the blue control signal BC, respectively.  
      The light source  210 ′ further includes a light mixing part  215 . The light mixing part  215  mixes the red, green and blue laser beam portions RL, GL and BL into a laser beam CL. In addition, the light mixing part  215  vibrates in a predetermined range with respect to a rotation angle to guide the laser beam CL so that the laser beam CL is irradiated to the light reflecting part  300  from a first end portion to a second end portion of a light reflecting part  300  that is a convex mirror, in sequence. Alternatively, the light mixing part  215  may include a light mixing portion and a light reflecting portion that is integrally formed on the light mixing portion.  
      According to this exemplary embodiment, the light mixing part  215  vibrates so that the laser beam CL guided by the light mixing part  215  is irradiated to different positions of the light reflecting part  300 . That is, the light mixing part  215  and the light modulator  220  shown in  FIG. 3  are integrally formed with each other so that additional vibration mirror may be omitted. The light reflecting part  300  reflects the modulated laser beam CL to be substantially parallel a front surface of the band  450 . As each of the first or second scanning mirrors  410  or  420  moves from position EP 1  to EP 2 , it reflects the laser beam CL to the back surface of the display unit  100 .  
       FIG. 5  is a plan view showing a light generating part and a light reflecting part of a display apparatus in accordance with another exemplary embodiment of the present invention.  FIG. 6  is a cross-sectional view showing a display apparatus having the light generating part and the light reflecting part shown in  FIG. 5 .  
      Referring to  FIGS. 1, 5 , and  6 , the light generating part  200  includes a light source  210 Δ that generates a laser beam having red, green and blue wavelengths.  
      The light source  210 ″ includes a red laser diode  211 , a green laser diode  212  and a blue laser diode  213 . The red laser diode  211  generates a red laser beam RL having the red wavelength based on a red control signal RC that is from a controlling part  550 . The green laser diode  212  generates a green laser beam GL having the green wavelength based on a green control signal GC that is from the controlling part  550 . The blue laser diode  213  generates a blue laser beam BL having the blue wavelength based on the blue control signal BC that is from the controlling part  550 . Intensities of the red, green and blue laser beam portions RL, GL and BL are determined by the red control signal RC, the green control signal GC and the blue control signal BC, respectively.  
      Each of the red, green and blue laser diodes  211 ,  212  and  213  vibrates in a predetermined range to guide each of the red, green and blue laser beam portions RL, GL and BL into different positions of the light reflecting part  300 . Alternatively, the red, green and blue laser beam portions RL, GL and BL may be reflected in the red, green and blue laser diodes  211 ,  212  and  213 , respectively, so that the red, green and blue laser beam portions RL, GL, and BL are guided.  
      The light reflecting part  300  may include a first convex mirror  310 , a second convex mirror  320 , and a third convex mirror  330 . The red laser beam RL is sequentially irradiated to adjacent portions of the first convex mirror  310 , and the red laser beam RL is then reflected from the first convex mirror  310  to substantially parallel a front surface of the band  450 . The green laser beam GL is sequentially irradiated to adjacent portions of the second convex mirror  320 , in sequence, and the green laser beam GL is then reflected from the second convex mirror  320  to substantially parallel a front surface of the band  450 . After the blue laser beam BL is sequentially irradiated to adjacent portions of the third convex mirror  330 , the blue laser beam BL is reflected from the third convex mirror  330  to substantially parallel a front surface of the band  450 . Each mirror  310 ,  320 , and  330  may be positioned such that the reflected RL, GL, and BL substantially overlaps before being reflected by the scanning mirror  410  or  420  to the back surface of the display unit  100 .  
       FIG. 7  is a cross-sectional view showing a display apparatus in accordance with another exemplary embodiment of the present invention.  FIG. 8  is an enlarged cross-sectional view showing a portion  11  shown in  FIG. 7 . Referring to  FIGS. 7 and 8 , a scanning unit  600  of the display apparatus  700  includes first, second, . . . nth scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  and a lifting part  620 . The lifting part  620  outwardly lifts the first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  towards the display unit  100  in a third direction D 3  that is substantially perpendicular the planar back surface of the display unit  100 . Unlike the rotatable scanning unit  560  of  FIGS. 1-6 , the scanning unit  600  does not rotate. Instead, the laser beam is sequentially scanned from a top portion EP 1  of the display unit&#39;s back surface to a bottom portion EP 2  of the display unit&#39;s back surface by sequentially raising the first, second . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , and  610 - n.    
      The first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  may be arranged in a first direction D 1  that substantially parallels the back surface of the display unit  100 . The scanning sections of the first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  are inclined with respect to the third direction D 3  by a predetermined angle so that a laser beam from the light reflecting part  300  is reflected from the first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  toward the back surface of the display unit  100 .  
      In use, the lifting part  620  sequentially lifts the first, second, . . . nth scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  in a third direction D 3  that is substantially perpendicular to the display unit  100 , so that positions on the display unit  100  is scanned are sequentially changed. In particular, the lifting part  620  moves the first scanning mirror  610 - 1  in the third direction D 3  at a predetermined speed. The laser beam from the light reflecting part  300  is reflected from the first scanning mirror  610 - 1  to be irradiated to the display unit  100 . When the first scanning mirror  610 - 1  is transported in the third direction D 3 , the laser beam is sequentially irradiated to the display unit  100 .  
      After the laser beam is scanned using the first scanning mirror  610 - 1 , the laser beam is also scanned by the second scanning mirror  610 - 2 . In particular, the lifting part  620  moves the second scanning mirror  610 - 2  in the third direction D 3  at the speed substantially same as that of the first scanning mirror  610 - 1 . The laser beam from the light reflecting part  300  is reflected from the second scanning mirror  610 - 2  to be irradiated to the display unit  100 . When the second scanning mirror  610 - 2  is transported in the third direction D 3 , the laser beam is sequentially irradiated to the display unit  100 .  
      After the laser beam is scanned using the second scanning mirror  610 - 2 , the laser beam is scanned by the third scanning mirror  610 - 3 . Thus the lifting part  620  sequentially moves the first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  to scan the laser beam on the display unit  100  using each of the first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n.    
      The lifted first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  may be simultaneously lowered. Alternatively, the first, second, . . . n th  scanning mirrors  610 - 1 ,  610 - 2 , . . .  610 - n  may be upwardly lifted and lowered, in sequence.  
      When a size of the display unit  100  increases, the number of the scanning mirrors increases so that the laser beam may be scanned on an entire surface of the scanning unit. In addition, when the size of the display unit  100  increases, a size of each of the scanning mirrors may also increase so that the laser beam may be scanned on the entire surface of the scanning unit. That is, the number of the scanning mirrors is determined by the sizes of the display unit  100  and the scanning mirrors.  
      An advantage of the invention is that the scanning unit includes the first and second scanning mirrors to scan an emitted laser beam to the display unit. That is, the first and second scanning mirrors alternately irradiate the laser beam to the display unit during alternate, sequential frames so that the recovery time period is omitted, thereby increasing a scanning speed of the scanning unit.  
      Alternatively, the scanning unit may include a plurality of scanning mirrors that are transported in a direction substantially perpendicular to the display unit, and are sequentially lifted, so that the laser beam is irradiated to the display unit. This configuration eliminates, the recovery time period, thereby increasing the scanning speed of the scanning unit.  
      This invention has been described with reference to various exemplary embodiments. It is evident, however, that many alternative modifications and variations will be apparent to those having skill in the art in light of the foregoing description. Accordingly, the present invention embraces all such alternative modifications and variations as fall within the spirit and scope of the appended claims.