Abstract:
A projection display device is discussed, which includes an optical system having an improved arrangement, thereby being capable of reducing the size of the projection display device.

Description:
This application claims the priority benefit of Korean Patent Application No. 10-2007-0112974, filed on Nov. 7, 2007 in Republic of Korea, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     The present invention relates to a projection display device for projecting an image onto an external screen, to display the projected image on the external screen. 
     2. Background 
     Various large-screen display devices have been developed and commercially available. Examples of such devices are a liquid crystal display device, a plasma display device, and a projection display device. 
     Among such large-screen display devices, the projection display device is generally referred to as a “projector”. The projector projects an image onto an external screen using an optical engine, and thus displays the image. 
     Such a projector is an apparatus capable of conveniently implementing a large-screen display. Recently, a projector having an ultra-mini size has been developed. Such a projector is referred to as a “pico-projector”. This projector is mainly equipped in a portable terminal. 
     SUMMARY OF THE INVENTION 
     The present invention provides a projection display device having a structure that allows the size and/or cost of the projection display device to be reduced or minimized. 
     An object of the present invention is to provide a projection display device having one or more optical elements for reflecting a light emitted from an illumination optical unit at an acute angle to an integrator, so as to reduce the size of the projection display device effectively. 
     Another object of the present invention is to provide a projection display device which addresses the limitations and disadvantages associated with the related art projection display devices. 
     According to an embodiment, the present invention provides a projection display device, comprising: an illumination optical unit configured to emit a light for illumination; an integrator configured to convert the light received from the illumination optical unit into a uniform light; an image projection unit configured to project an image onto an external screen, using the uniform light emitted from the integrator; and a reflection mirror arranged between the illumination optical unit and the integrator, to reflect the light emitted from the illumination optical unit at a first acute angle to the integrator. 
     According to an embodiment, the present invention provides projection display device comprising: an illumination optical unit configured to emit a light for illumination; an integrator arranged on a first optical path, to convert the light emitted from the illumination optical unit into a uniform light; and an image projection unit configured to receive the uniform light emitted from the integrator and to project a light on a second optical path so as to project an image onto an external screen, wherein the integrator and the image projection unit are arranged such that the first and second optical paths form an acute angle. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a functional block diagram schematically illustrating a projection display device according to an embodiment of the present invention; 
         FIG. 2  is a schematic view illustrating a projection display device according to a related art; 
         FIG. 3  is a schematic view illustrating a first embodiment of a projection display device according to the present invention; 
         FIG. 4  is a schematic view illustrating a second embodiment of a projection display device according to the present invention; 
         FIG. 5  is a schematic view illustrating a third embodiment of a projection display device according to the present invention; 
         FIGS. 6A and 6B  are schematic views illustrating two examples of a configuration of a display panel type image projection unit according to the present invention; 
         FIG. 7  is a schematic view illustrating an example of a configuration of a scanner type image projection unit according to the present invention; 
         FIG. 8  is a perspective view illustrating an example of a micro scanner according to the present invention; and 
         FIG. 9  is a plan view for explaining connectors provided at the micro scanner of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention associated with a projection display device, examples of which are illustrated in the accompanying drawings. However, the scope of the present invention is not limited to the following embodiments and drawings. Although a suffix “module” or “unit” is used for constituent elements described in the following description, it is intended only for easy description of the specification. The suffix itself has no meaning or function to distinguish the constituent element using the suffix from the constituent element using no suffix. 
     It can be appreciated by a skilled person that the projection display device according to various embodiments of the present invention may be implemented in the form of a pico-projector, and may be internally or externally equipped in an electronic device including a portable terminal such as a mobile phone, a smart phone, a notebook (laptop) computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a GPS, or a navigation terminal, or in a fixed terminal such as a digital TV or a desktop computer. 
     Hereinafter, the constituent elements of the projection display device according to an embodiment of the present invention will be described with reference to  FIG. 1 . 
       FIG. 1  is a functional block diagram schematically illustrating the projection display device according to an embodiment of the present invention. 
     First, the overall configuration of the projection display device  100  according to the present invention will be described with reference to  FIG. 1 . 
     The projection display device  100  according to the present invention includes an illumination optical unit  110 , an image projection unit  120 , an input unit  130 , a memory  140 , a power supply unit  150 , and a control unit  160 . All the components of the projection display device  100  are operatively coupled and configured. 
     Of course, the projection display device  100  according to the present invention may further include other elements, if necessary or desired, in addition to the above-described constituent elements. However, no detailed description will be given of these additional elements, for simplicity of description, because the additional elements have no direct relation with the present invention. 
     Meanwhile, it should be noted that each of the above-described constituent elements may be combined with another constituent element to form one constituent element, or may be divided into two or more constituent elements. 
     Now, the constituent elements of the projection display device  100  according to an embodiment of the present invention will be described in more detail. 
     The illumination optical unit  110  includes a light source  111  (e.g.,  111   a ,  111   b ,  111   c  in  FIGS. 3-5 ), a synthesizer  112  (e.g.,  112   a ,  112   b  in  FIGS. 3-5 ), and an integrator  113 . 
     The image projection unit  120  projects an image onto an external screen, using the light emitted from the illumination optical unit  110 , to provide the image to a user. 
     The input unit  130  includes one or more of a key pad, a dome switch, a touch pad (constant voltage/constant current), buttons, switches, a jog wheel, a jog switch, etc. The input unit  130  generates input data, which is used to control the operation of the projection display device  100  according to the present invention. 
     Where the projection display device  100  according to the present invention is internally or externally equipped in a portable terminal such as a mobile phone, a smart phone, a notebook (laptop) computer, a digital broadcast terminal, a PDA, a PMP, or a navigation terminal, or in a fixed terminal such as a digital TV or a desktop computer, the input unit  130  may be an operating unit equipped in the portable terminal or fixed terminal. 
     The memory  140  may store therein programs and any other information/data for controlling the projection display device  100  according to the present invention, or may perform functions for temporarily storing input/output data. 
     The memory  140  may include at least one storage medium selected from a flash memory type memory, a hard disk type memory, multimedia card micro type memory, a card type memory (for example, an SD or XD memory), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically-erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disc, and an optical disc. 
     The power supply unit  150  supplies power to the constituent elements of the projection display device  100  under the control of the control unit  160 . 
     The control unit  160  controls the overall operation of the projection display device  100  according to the present invention. When a key signal for driving the projection display device  100  is input through the input unit  130 , the control unit  160  controls the illumination optical unit  110  and image projection unit  120 , to project an image onto the screen. 
     Where the projection display device according to the present invention is internally or externally equipped in a portable terminal such as a mobile phone, a smart phone, a notebook (laptop) computer, a digital broadcast terminal, a PDA, a PMP, or a navigation terminal, or in a fixed terminal such as a digital TV or a desktop computer, the control unit  160  may be a controller equipped in the portable terminal or fixed terminal. 
     The projection display device  100  according to the present invention having the above-described configuration can have a reduced or minimal size because the angle between the optical incidence and outgoing paths of the image projection unit  120  is an acute angle, which is smaller than the right angle. As a result, a more compact projection display device can be provided. 
     For contrasting purposes,  FIG. 2  is a schematic view illustrating a projection display device according to the related art. As shown in  FIG. 2 , the conventional projection display device includes an illumination optical unit  10  for emitting light, a display element  22  for producing an image using the light emitted from the illumination optical unit  10 , a reflection mirror  21  for reflecting the light emitted from the illumination optical unit  10  toward the display element  22 , and a projection optical unit  23  for projecting the image produced by the display element  22  onto an external screen. The illumination optical unit  10  includes first to third light sources  11   a ,  11   b , and  11   c  for emitting red (R) light, green (G) light, and blue (B) light, respectively, two dichroic mirrors  12   a  and  12   b , and an integrator  13  for converting the light emerging from the dichroic mirrors  12   a  and  12   b  into a uniform light. 
     As shown in  FIG. 2 , the integrator  13  is arranged on a light incidence path I of the display element  22 . The projection optical unit  23  is arranged on a light outgoing path II of the display element  22 . The light incidence path I, on which the integrator  12  is arranged, and the light outgoing path II, on which the projection optical unit  23  is arranged, form a right angle therebetween. As a result, the conventional projection display device of  FIG. 2  has a problem in that there is a limitation in miniaturizing the projection display device because the integrator  13  is longitudinally arranged along the optical incidence path I and the paths I and II form a right angle, so that the occupation space of the components of the related art projection display device is large. 
     To address these limitations and disadvantages associated with the related art projection display devices, in accordance with the present invention, the angle between the light incidence path and the light outgoing path is adjusted to be within an acute angle range. Also, the integrator  113  is arranged on the adjusted light incidence path, and the image projection unit  120  is arranged on the adjusted light outgoing path. Accordingly, it is possible to reduce the overall size of the projection display device  100  effectively in the present invention. 
     Hereinafter, embodiments of the present invention will be described in detail with reference to  FIGS. 3 to 9 . The projection display devices of  FIGS. 3-9  preferably have the functional components shown in  FIG. 1 , but may have other or additional components. 
       FIG. 3  is a schematic view illustrating a first embodiment of the projection display device according to the present invention. 
     Referring to  FIG. 3 , the illumination optical unit  110  (light source unit) of the projection display device includes first to third light emitting diodes (LEDs)  111   a ,  111   b , and  111   c  for emitting R light, G light, and B light, respectively. The LEDs  111   a ,  111   b , and  111   c  generate and emit the R light, G light, and B light, respectively, in accordance with the drive current supplied from the power supply unit  150  under the control of the control unit  160 . In another example, the light source unit  110  may include laser diodes or other types of light sources, in place of the LEDs. 
     The synthesizer  112  ( 112   a ,  112   b ) performs a selective transmission/reflection for the light emitted from the light source unit  110 , and then sends the resultant light toward the image projection unit  120 , in order to produce an image. 
     The synthesizer  112  may include a plurality of dichroic mirrors, for example, first and second dichroic mirrors  112   a  and  112   b . Each of the first and second dichroic mirrors  112   a  and  112   b  is a mirror for selectively reflecting or transmitting only the light of a particular wavelength, to obtain the light of a desired wavelength band. Each of the first and second dichroic mirrors  112   a  and  112   b  transmits or reflects a selected one of the light beams emitted from the LEDs  111   a ,  111   b , and  111   c.    
     Particularly, the first dichroic mirror  112   a  may be arranged at a position where the R light and G light cross each other. As a result, the first dichroic mirror  112   a  is configured to transmit the R light while reflecting the G light, so that it emits the R light and G light. 
     The second dichroic mirror  112   b  is configured to transmit the R light and G light emerging from the first dichroic mirror  112   a  while reflecting the B light, so that it emits the R light, G light, and B light. 
     Thus, the R light, G light, and B light are synthesized while they are processed through the two dichroic mirrors  112   a  and  112   b  so that they produce the light of various colors in accordance with an image to be produced. 
     Although the above description has been given under the assumption that the first dichroic mirror  112   a  is arranged at the position where the R light and G light cross each other, the positions of the dichroic mirrors  112   a  and  112   b  according to the present invention are not limited thereto, and can vary as applicable. 
     Meanwhile, although not shown in  FIG. 3 , a condensing lens and/or a collimating lens may be arranged between each of the LEDs  111   a ,  111   b , and  111   c  and the corresponding mirror  112   a  or  112   b . In this case, the condensing lens can function to condense the light emitted from the LEDs  111   a ,  111   b , and  111   c , whereas the collimating lens can function to convert the light condensed by the condensing lens into a collimated light, and then to send the collimated light to the synthesizer  112 . 
     The integrator  113  is arranged on the light incidence path I of the image projection unit  120 . The integrator  113  shapes the light emerging from the first and second dichroic mirrors  112   a  and  112   b  such that the light has a uniform intensity. The integrator  113  may include at least one of a fly eye lens, a rod lens, a light tunnel or funnel having a box-shaped mirror, or a trapezoidal light funnel. 
     Meanwhile, the reflection mirror  170  is disposed between the dichroic mirror  112   b  and the integrator  113 , and reflects the light emerging from the first and second dichroic mirrors  112   a  and  112   b  by an angle θ 1  defined within a negative (−) acute angle range larger than 180°, but smaller than 270° such that the reflected light is directed to the integrator  113  arranged on the light incidence path I. 
     That is, in accordance with the first embodiment of the present invention, the light incidence path I and the light outgoing path II form an acute angle θ 1 , for example, the angle θ 1  defined within the negative (−) acute angle range, and the integrator  113  and image projection unit  120  are arranged on the light incidence path I and light outgoing path II, respectively. Further, the light paths I and II between the integrator  113  and the external screen form an acute angle. 
     In the example of  FIG. 3 , the image projection unit  120  is arranged beneath or below the illumination optical unit  110 . For example, the reflection mirror  170  reflects the light from the dichroic mirrors  112   a  and  112   b  in a downward acute angle direction. Accordingly, it is possible to reduce the total system length of the projection display device, and thus to minimize or reduce the size of the projection display device, as compared to the related art projection display devices. 
       FIG. 4  is a schematic view illustrating a second embodiment of the projection display device according to the present invention. 
     Referring to  FIG. 4 , the reflection mirror  170  according to the second embodiment of the present invention reflects the light emerging from the first and second dichroic mirrors  112   a  and  112   b  by an angle θ 2  defined within a positive (+) acute angle range larger than 0°, but smaller than 90° such that the reflected light is directed to the integrator  113  arranged on the light incidence path I. 
     That is, in accordance with the second embodiment of the present invention, the light incident on the reflection mirror  170  and the light reflected from the reflection mirror  170  form an acute angle θ 2 . Further, the light incidence path I and the light outgoing path II form the angle θ 2  defined within the positive (+) acute angle range, where the integrator  113  and image projection unit  120  are arranged on the light incidence path I and light outgoing path II, respectively. 
     Moreover, in the example of  FIG. 4 , the image projection unit  120  is arranged over or above the illumination optical unit  110 . For example, the reflection mirror  170  reflects the light from the dichroic mirrors  112   a  and  112   b  in an upward acute angle direction. Accordingly, it is possible to reduce the total system length of the projection display device, and thus to minimize or reduce the size of the projection display device, as compared to the related art projection display devices. 
       FIG. 5  is a schematic view illustrating a third embodiment of the projection display device according to the present invention. 
     Referring to  FIG. 5 , the projection display device according to the third embodiment includes a plurality of reflection mirrors, for example, first and second reflection mirrors  170  and  180 . 
     The first reflection mirror  170  reflects the light emerging from the first and second dichroic mirrors  112   a  and  112   b  by an acute angle, e.g., an angle θ 1  defined within a negative (−) acute angle range larger than 180°, but smaller than 270°, such that the reflected light is directed to the integrator  113  arranged on the light incidence path I. Further, the integrator  113  is disposed below the first reflection mirror  170 . 
     The second reflection mirror  180  reflects the light emerging from the integrator  113  by an acute angle, e.g., an angle θ 2  defined within a positive (+) acute angle range larger than 0°, but smaller than 90°, such that the reflected light is directed towards the image projection unit  120  arranged on the light outgoing path II. 
     Thus, it is possible to minimize or reduce the overall size of the projection display device by adjusting the angle between the light incidence path I and the light outgoing path II such that the angle is within an acute angle range, and arranging the integrator  113  and image projection unit  120  on the adjusted light incidence path I and light outgoing path II, respectively. 
     In each projection display device of  FIG. 3 ,  4  or  5 , the image projection unit  120  produces an image, using the light emerging from the optical path unit  120 , under the control of the control unit  160 , and then projects the produced image onto an external screen, to display the image. 
     The image projection unit  120  may be classified into a display panel type or a scanner type, but can be of a different type. Hereinafter, two examples of the configuration of the image projection unit  120 , which is of a display panel type, will be described with reference to  FIGS. 6A and 6B . 
     Referring to  FIGS. 6A and 6B , the display panel type image projection unit  120  according to an embodiment of the present invention includes a reflection plate  121 , a display panel  122 , and a projection lens  123 . The display panel  122  receives the light emerging from the integrator  113  via the reflection plate  121 , and projects an image onto the screen, using the received light. The display panel  122  may comprise a reflection type imaging unit such as a digital micro mirror device or a reflection type liquid crystal display device, or a transmission type imaging unit. The reflection type imaging unit selectively reflects the incident light by pixels, to form an image, whereas the transmission type imaging unit may selectively transmit the incident light to form an image. 
     Meanwhile, the projection lens  123  projects the image produced by the display panel  122  onto the screen in an enlarged state. 
     The display panel type image projection unit  120  shown in  FIG. 6A  may be applied to the image projection unit  120  shown in  FIG. 5 . In this case, a third reflection plate  190  of  FIG. 5  corresponds to the reflection plate  121  of  FIG. 6A . 
     On the other hand, the display panel type image projection unit  120  shown in  FIG. 6B  may be applied to the image projection unit  120  shown in  FIG. 3  or  4 . 
     Now, the configuration of the image projection unit  120 , which is of a scanner type, will be described with reference to  FIGS. 7 to 9 . 
       FIG. 7  is a schematic view illustrating an example of the scanner type image projection unit according to the present invention. 
     Referring to  FIG. 7 , the scanner type image projection unit  120  according to the present invention includes a reflection plate  121  and a scanner  124 . 
     Where the scanner type image projection unit  120  of  FIG. 7  is applied to the case of  FIG. 3  or  4 , the reflection plate  121  may be dispensed with. In this case, the light emerging from the integrator  113  may be directly incident to the scanner  124 . 
     On the other hand, where the scanner type image projection unit  120  of  FIG. 7  is applied to the case of  FIG. 5 , the third reflection plate  190  of  FIG. 5  may be replaced by the reflection plate  121  of  FIG. 7 . 
     The scanner  124  reflects the light received via the reflection plate  121  in a horizontal or vertical direction or in the horizontal and vertical directions, to raster-scan the reflected light onto the screen. 
     The scanner  124  includes at least one micro scanner having a rotatable mirror. As an example of the micro scanner, a biaxially-driven micro scanner is shown in  FIGS. 8 and 9 . 
     Hereinafter, an example of the micro scanner will be described in detail with reference to  FIGS. 8 and 9 . 
       FIG. 8  is a perspective view illustrating an example of the micro scanner according to the present invention.  FIG. 9  is a plan view for explaining connectors provided at the micro scanner of  FIG. 8 . 
     As shown in  FIGS. 8 and 9 , the micro scanner includes a mirror plate  51  including a thin film formed with a reflection surface for reflecting a laser light, and a frame arranged beneath the thin film to support the thin film, an outer frame  52  arranged to be outwardly spaced apart from the periphery of the mirror plate  51 , a plurality of connectors  53 A,  53 B, and  54  for connecting the mirror plate  51  and the outer frame  52 , and a gimbal  56  arranged to be outwardly spaced apart from the periphery of the outer frame  52 . The micro scanner also includes a pair of inner elastic flexible members  57  symmetrically formed with respect to the mirror plate  51 , and connected to the gimbal  56  and to the outer frame  52 , and a pair of outer elastic flexible structures  58  symmetrically formed with respect to the mirror plate  51 , and connected to the gimbal  56  and to a pair of support members  75 , to upwardly raise the mirror plate  51 , outer frame  52 , and gimbal  56 . 
     As shown in  FIG. 9 , the plural connectors  53 A,  53 B, and  54  functioning to connect the mirror plate  51  and the outer frame  52  include first connectors, namely, the connectors  54 , and second connectors, namely, the connectors  53 A and  53 B. The second connectors  53 A and  53 B are formed on a first line P 1  connecting the outer elastic flexible members  58  such that they are symmetrical with respect to the mirror plate  51 . The first connectors  54  are formed on a second line P 2  perpendicular to the first line P 1  such that they are symmetrical with respect to the mirror plate  51 . The second connector  53 A includes two symmetrical portions  53 A- 1  and  53 A- 2 , whereas the second connector  53 B includes two symmetrical portions  53 B- 1  and  53 B- 2 . 
     The gimbal  56  is connected to the outer frame  52  by the inner elastic flexible members  57 . The gimbal  56  is also connected to the support members  75  by the outer elastic flexible members  58  symmetrically formed on a line perpendicular to the inner elastic flexible members  57 . 
     The outer elastic flexible members  58  connect the gimbal  56  to the support members  75  such that the mirror plate  51 , outer frame  52 , and gimbal  56  are upwardly raised. In the drawings, only a portion of each support member  75  is schematically shown. 
     The inner and outer elastic flexible members  57  and  58  provide a recovering torque during operation of the micro mirror while functioning as rotating axes. That is, the outer frame  52  rotates about the inner elastic flexible members  57  as an axis (this axis extends a line X- X′, as shown in  FIG. 8 , and is referred to as an “X-axis”). The gimbal  56  rotates about the outer elastic flexible members  58  as an axis (this axis extends a line Y-Y′, as shown in  FIG. 8 , and is referred to as a “Y-axis”). 
     The micro scanner  124  having the above-described structure can perform rotating operations with 2 axial degrees of freedom. That is, the micro scanner  124  can rotate not only about the inner elastic flexible members  57 , namely, the X-axis, but also about the outer elastic flexible members  58 , namely, the Y-axis. The axial rotations of the micro scanner  124  do not have influence on each other, so that they can be independently controlled. Accordingly, it is possible to implement a micro mirror capable of being inclined from a 2-dimensional plane by an arbitrary angle. 
     When the above-described micro scanner  124  is used, the scanning operation is carried out in accordance with a micro rotation of the mirror plate  51 . Accordingly, sweeping can be carried out at a very high speed. 
     Although the embodiments of the present invention have been described in conjunction with particular matters such as concrete constituent elements, the illustrative embodiments and the accompanying drawings, they are intended only to facilitate understanding of the invention. Accordingly, the present invention is not limited to such matters, embodiments and drawings. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. 
     Thus, it is intended that the present invention is not limited to the above-described embodiments, and covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.