Abstract:
A microminiaturized projection module for projecting an image onto an object is disclosed in the present invention. The module includes a number of light units each for providing red, green, and blue beams; an image processing unit for receiving the image, dividing the image into n×m image signals, and transforming each of the image signals into a modulating signal and a direction signal, where n and in are integrals not less than 2, respectively; a number of modulation units for modulating the beams from one light unit according to the modulating signal received from the image processing unit and sending out the modulated beams simultaneously; and an array of n×m mirrors for projecting the modulated beams to form the image onto the object according to the direction signal received from the image processing unit. The invention has advantages that can reduce modulation speed, undergo slight shock and be free from raster pinch effect.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a microminiaturized projection module. More specifically, the present invention relates to a microminiaturized projection module for projecting an image onto any object with an array of mirrors. 
     BACKGROUND OF THE INVENTION 
     Projectors used in daily life are manufactured based on 3LCD, Digital Light Processing (DLP) or Liquid Crystal on Silicon (LCoS) technology. Although the color models and projection principles are different from each other, these technologies separate white light beams from high voltage halogen lamps or mercury vapor lamps into red (R), green (G) and blue (B) beams by dichronic mirrors, panels or color wheels. However, as to requirement of portability for every device people use in daily life, bulky size of the projectors manufactured by the projection methods with traditional lamps can not be further reduced. Therefore, it is inevitable to use light emitting diode (LED) or visible laser diode (LD) to replace the traditional lamps as a solution for miniaturized projectors. 
     Recently, projector manufacturers start to use three-primary-color (RGB) LED or visible LD. LED or visible LD has small volume. By using DLP and LCoS technologies with these light sources, lighting devices can be effectively simplified so that the projector can be more compact. Meanwhile, LED or visible LD has more advantages that traditional lamps don&#39;t have. For example, LED or visible LD can be switched on swiftly, operate noiselessly and have longer lifetime so that user doesn&#39;t have to change LED or visible LD often. 
     A visible laser is a laser with a beam that can be seen by the naked eye. Through a process known as stimulated emission, laser releases light beams, or electromagnetic radiation. Essentially, an electron is stimulated and moves to an area of lower energy. The energy lost takes the form of a photon, a unit of electromagnetic radiation, and is emitted in the form of a laser beam. Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses. Hence, compared with LED, a visible laser diode can emit beams for a longer transmission distance. Images sent via laser beams are not interfered with a multi-directional light source. Therefore, mini projectors (or called pico projectors) often use visible laser diodes as a light source. 
     Several inventions disclose designs of a projecting system using laser diodes as a light source. Please refer to  FIG. 1 . U.S. Pat. No. 7,252,394 provides a projection display system which includes a light source emitting a light beam, and a reflecting mirror system for scanning the light beam over an image to illuminate the image. The light source can be a solid state device such as a laser diode. The reflecting mirror system can be one or more MEMS scanning mirrors that rotate to raster scan the light beam over the image. The image can be an advertisement located on a wall, a screen, a sign, or a billboard. The image can also be a semi-transparent image that is projected onto a medium to produce a larger image. The reflecting mirror system has one vertically scanning mirror and at least one horizontally scanning mirror. Hence, a raster scanning over one complete screen or more discrete tiles can be achieved. However, although only one vertically scanning mirror is able to perform raster scanning, it is hard to coordinate other horizontally scanning mirrors with the vertically scanning mirror. For a screen composed of several tiles, there would be many malpositions or even tile overlapping occurred due to the problem. When the device is slightly shocked, the whole screen will become unstable as well. 
       FIG. 2  shows U.S. Pat. No. 7,209,271. &#39;271 provides a display apparatus which includes a scanning assembly that scans about two or more axes, typically in a raster pattern. A number of light sources emit light from spaced apart locations toward the scanning assembly so that the scanning assembly simultaneously scans more than one of the beams. The light sources are positioned so that their beams each illuminate discrete regions of the image field that are substantially non-overlapping with respect to the other discrete regions. The image is thus formed from a set of tiles. By activating a first light source during a forward sweep of the mirror and activating a second light source during a reverse sweep of the mirror, a common line can be written during a single sweep of the mirror. Shifting the position of the sources such that the two halves are aligned reduces raster pinch. The invention points out the problem of raster pinch effect and provides a solution to it. However, the modulator for controlling color model has heavy work load. The device can not work properly under slight shock. 
     The objects of the present invention are to solve the problems mentioned above. Meanwhile, it has effect to reduce modulation speed. Each modulator can have a longer life time and be easily repaired. 
     SUMMARY OF THE INVENTION 
     This paragraph extracts and compiles some features of the present invention; other features will be disclosed in the follow-up paragraphs. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims. 
     In accordance with an aspect of the present invention, a microminiaturized projection module for projecting an image onto an object, comprising: a plurality of light units each for providing red, green, and blue beams; an image processing unit for receiving the image, dividing the image into n×m image signals, and transforming each of the image signals into a modulating signal and a direction signal, where n and m are integrals not less than 2, respectively; a plurality of modulation units for modulating the beams from one light unit according to the modulating signal received from the image processing unit and sending out the modulated beams simultaneously; and an array of n×m mirrors for projecting the modulated beams to form the image onto the object according to the direction signal received from the image processing unit; wherein the modulation units have an amount not less than n×m, and the light units have an amount same as that of the modulation units. 
     Preferably, the modulation units send the modulated beams to the mirrors one to one when the modulation units are n×m. 
     Preferably, at least one mirror receives the modulated beams from at least two modulation units when the modulation units are more than n×m. 
     Preferably, the mirror is a 2-axis torsion mirror. 
     Preferably, the mirror, having a horizontal-axle and a vertical-axle, can rotate horizontally relative to the vertical-axle and vertically relative to the horizontal-axle, and has mechanical rotation angles up to ±10°, respectively. 
     Preferably, the mirror comprises two single-axle torsion mirrors. 
     Preferably, one of the two single-axle torsion mirrors scans faster than the other. 
     Preferably, the two single-axle torsion mirrors each has an axle perpendicular to each other. 
     Preferably, the mirror is driven by electromagnetic forces, electrostatic forces, piezoelectric forces or the combination thereof. 
     Preferably, the mirror is made of semiconductor, metal or polymer. 
     Preferably, the mirror is made by micro-electro-mechanical system (MEMS) technology. 
     Preferably, the image is scanned via raster scanning or Lissajous scanning. 
     Preferably, the light units comprise visible laser diodes. 
     Preferably, the light unit emits green light by diode pumped solid-state (DPSS) technology. 
     Preferably, the modulation units comprise acoustic-optic modulators, magneto-optic modulators, or electro-optic modulators for independently modulating the red, green and blue beams generated by the light units. 
     Preferably, the mirror rotates horizontally and vertically according to the direction signal to project the modulated beams onto the object. 
     Preferably, the object is a wall, a screen, a table surface or a billboard. 
     Preferably, the object has planar, curved or rough surface. 
     Preferably, the object is divided into n columns and in rows and each of the mirrors scans on a specified region formed by intersection of a column and a row. 
     Preferably, the columns have the same width. 
     Preferably, the rows have the same length. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a prior art. 
         FIG. 2  illustrates another prior art. 
         FIG. 3  shows a first embodiment of the present invention. 
         FIG. 4  shows a block diagram of a light unit in the first embodiment. 
         FIG. 5  shows a mirror structure in the first embodiment, 
         FIG. 6  shows how an image is projected in the first embodiment. 
         FIG. 7  shows a second embodiment of the present invention. 
         FIG. 8  shows a block diagram of a light unit in the second embodiment. 
         FIG. 9  shows a mirror structure in the second embodiment. 
         FIG. 10  shows how an image is projected in the second embodiment. 
         FIG. 11  shows a third embodiment of the present invention. 
         FIG. 12  shows a block diagram of a light unit in the third embodiment. 
         FIG. 13  shows how an image is projected in the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For better understanding of the present invention, three embodiments are described below. 
     First Embodiment 
     Please refer to  FIG. 3  to  FIG. 6 . A first embodiment is illustrated.  FIG. 3  shows a microminiaturized projection module  10  and a planar screen  20  for forming an image. The microminiaturized projection module  10  has an image processing unit  102  for receiving the image, dividing the image into four (2×2) image signals, and transforming each of the image signals into a modulating signal and a direction signal. The microminiaturized projection module  10  also has a first light unit  111 , a second light unit  112 , a third light unit  113  and a fourth light unit  114 . Each light unit provides red, green, and blue beams. A first modulation unit  121 , a second modulation unit  122 , a third modulation unit  123  and a fourth modulation unit  124  are connected with the first light unit  111 , the second light unit  112 , the third light unit  113  and the fourth light unit  114  respectively. Each modulation unit modulates the beams from the corresponding light unit according to the modulating signal received from the image processing unit  102  and sends out the modulated beams simultaneously. The modulation units comprise acoustic-optic modulators for independently modulating the red, green and blue beams generated by the light units. 
     The microminiaturized projection module  10  further has a first mirror  131 , a second mirror  132 , a third mirror  133  and a fourth mirror  134 . The four mirrors form a 2×2 array. The mirrors are made of semiconductor and can be driven electromagnetically, electrostatically, or piezoelectrically. 
     The first mirror  131 , the second mirror  132 , the third mirror  133  and the fourth mirror  134  project the modulated beams from the first modulation unit  121 , the second modulation unit  122 , the third modulation unit  123  and the fourth modulation unit  124  respectively and form the image onto the screen  20  according to the corresponding direction signal received from the image processing unit  102 . It is obvious that the corresponding relation between modulation units and mirrors is one to one. 
     Please refer to  FIG. 4 . It shows a block diagram of the first light unit  111 . The first light unit  111  comprises a red visible laser diode  1111 , a blue visible laser diode  1112 , and a green visible laser emitter  1113 . It should be stressed that a natural green visible laser has not been invented. Therefore, the green visible laser emitter  1113  uses pumped solid-state (DPSS) technology. The second light unit  112 , the third light unit  113  and the fourth light unit  114  have the same internal structure. No further diagram is needed for illustrating purpose. 
     Next,  FIG. 5  shows how the mirrors work to reflect the beams received from the modulation units. Take the first mirror  131  for example. The first mirror  131  comprises two single-axle torsion mirrors, i.e., a vertical-axle torsion minor  1311  and a horizontal-axle torsion mirror  1312 . The vertical-axle torsion mirror  1311  can rotate around a vertical axle and the horizontal-axle torsion mirror  1312  can rotate around a horizontal axle. Both have mechanical rotation angles up to ±10°. The vertical axle is perpendicular to the horizontal axle. When a modulated beam comes to the first mirror  131 , the first mirror  131  adjusts angles of the vertical-axle torsion mirror  1311  and the horizontal-axle torsion mirror  1312  according to the direction signal from the image processing unit  102 . Therefore, the modulated beam will be reflected vertically then horizontally. Finally, it is projected onto a specified location on the screen  20 . 
     Please see  FIG. 6 . It shows how the image is projected onto the screen  20 . The first mirror  131 , the second mirror  132 , the third mirror  133  and the fourth mirror  134  are used to scan one-fourth of the image. When the image is projected, the screen  20  can be divided into four tiles with 2 columns and 2 rows accordingly. They are a first tile  201 , a second tile  202 , a third tile  203  and a fourth tile  204 . The columns have the same width and so do the rows. Hence, every tile has the same area. There is no overlap of any two tiles.  FIG. 6  also shows the scanning process. In the present invention, the image is scanned via raster scanning. Therefore, the vertical-axle torsion mirror  1311  rotates slower than the horizontal-axle torsion mirror  1312  because raster scanning needs faster horizontal scanning. In practice, scanning process is not limited to raster scanning. Sometimes, Lissajous scanning is used for a solid image. 
     Since there are four independent modulation units, modulation speed of each one can be reduced. If one of the modulation units doesn&#39;t work well, it is easy to repair the module by replacing the bad one. Meanwhile, the present invention can undergo slight shock without damaging the whole image. 
     Second Embodiment 
     Please refer to  FIG. 7  to  FIG. 10 . A second embodiment is illustrated.  FIG. 7  shows a microminiaturized projection module  30  and a rough billboard  40  for forming an image. The microminiaturized projection module  30  has an image processing unit  302  for receiving the image, dividing the image into six (3×2) image signals, and transforming each of the image signals into a modulating signal and a direction signal. The microminiaturized projection module  30  also has a first light unit  311 , a second light unit  312 , a third light unit  313 , a fourth light unit  314 , a fifth light unit  315  and a sixth light unit  316 . Each light unit provides red, green, and blue beams. A first modulation unit  321 , a second modulation unit  322 , a third modulation unit  323 , a fourth modulation unit  324 , a fifth modulation unit  325  and a sixth modulation unit  326  are connected with the first light unit  311 , the second light unit  312 , the third light unit  313 , the fourth light unit  314 , the fifth light unit  315  and the sixth light unit  316  respectively. Each modulation unit modulates the beams from the corresponding light unit according to the modulating signal received from the image processing unit  302  and sends out the modulated beams simultaneously. The modulation units comprise magneto-optic modulators for independently modulating the red, green and blue beams generated by the light units. 
     The microminiaturized projection module  30  further has a first mirror  331 , a second mirror  332 , a third mirror  333 , a fourth mirror  334 , a fifth mirror  335  and a sixth mirror  336 . The six mirrors form a 3×2 array. The mirrors are made of steel and driven electromagnetically. 
     The first mirror  331 , the second mirror  332 , the third mirror  333 , the fourth mirror  334 , the fifth mirror  335  and the sixth mirror  336  project the modulated beams from the first modulation unit  321 , the second modulation unit  322 , the third modulation unit  323 , the fourth modulation unit  324 , the fifth modulation unit  325  and the sixth modulation unit  326  respectively and form the image onto the billboard  40  according to the corresponding direction signal received from the image processing unit  302 . It is obvious that the corresponding relation between modulation units and mirrors is one to one like the first embodiment. The mirrors are made by micro-electro-mechanical system (MEMS) technology. 
     Please refer to  FIG. 8 . It shows a block diagram of the first light unit  311 . The first light unit  311  comprises a red light emitting diode  3111 , a blue light emitting diode  3112 , and a green light emitting diode  3113 . The second light unit  312 , the third light unit  313 , the fourth light unit  314 , the fifth light unit  315  and the sixth light unit  316  have the same internal structure. No further diagram is needed for illustrating purpose. 
     Next,  FIG. 9  shows how the mirrors work to reflect the beams received from the modulation units. Take the first mirror  331  for example. The first mirror  131  is a 2-axis torsion mirror. It has a horizontally rotating element  3311 , a horizontal-axle  3312 , a vertically rotating element  3313  and a vertical-axle  3314  so that the first mirror  331  can rotates horizontally relative to the vertical-axle and vertically relative to the horizontal-axle. The first mirror  331  has mechanical rotation angles in both vertical and horizontal direction up to ±10°. When a modulated beam comes to the first mirror  331 , the first mirror  331  adjusts angles by rotating around the horizontal-axle  3312  and the vertical-axle  3314  according to the direction signal from the image processing unit  302 . Therefore, the modulated beam will be reflected. Finally, it is projected onto a specified location on the billboard  40 . 
     Please see  FIG. 10 . It shows how the image is projected onto the billboard  40 . The first mirror  331 , the second mirror  332 , the third mirror  333 , the fourth mirror  334 , the fifth mirror  335  and the sixth mirror  336  are used to scan one part of the image. When the image is projected, the billboard  40  can be divided into six tiles with 3 columns and 2 rows accordingly. Obviously, every tile doesn&#39;t have the same area. They are a first tile  401 , a second tile  402 , a third tile  403 , a fourth tile  404 , a fifth tile  405  and a sixth tile  406 . There is no overlap of any two tiles.  FIG. 10  also shows that the second embodiment has the same scanning process as that of the first embodiment. In the present invention, the image is scanned via raster scanning. The combined motion of the two scanning directions form a sinusoidal raster in the vertical direction and cause non-uniform line spacing for the case of bidirectional scanning as if the forward and backward half-period raster lines are pinched near the edge of the display screen. Raster pinch effect degrades the image quality, especially for multi-beam scanning systems. In the present invention, in order to reduce the raster pinch effect, the first tile  401 , the third tile  403 , the fourth tile  404 , and a sixth tile  406  located on the edge of the image have double scanning frequency and half brightness as those of the second tile  402  and the fifth tile  405 . Raster pinch effect can be reduced thereby. 
     Third Embodiment 
     Please refer to  FIG. 11  to  FIG. 13 . A third embodiment is illustrated,  FIG. 11  shows a microminiaturized projection module  50  and a curved surface  60  for showing an image. The microminiaturized projection module  50  has an image processing unit  502  for receiving the image, dividing the image into four (2×2) image signals, and transforming each of the image signals into a modulating signal and a direction signal. The microminiaturized projection module  50  also has a first light unit  511 , a second light unit  512 , a third light unit  513 , a fourth light unit  514 , a fifth light unit  515  and a sixth light unit  516 . Each light unit provides red, green, and blue beams. A first modulation unit  521 , a second modulation unit  522 , a third modulation unit  523 , a fourth modulation unit  524 , a fifth modulation unit  525  and a sixth modulation unit  526  are connected with the first light unit  511 , the second light unit  512 , the third light unit  513 , the fourth light unit  514 , the fifth light unit  515  and the sixth light unit  516  respectively. Each modulation unit modulates the beams from the corresponding light unit according to the modulating signal received from the image processing unit  502  and sends out the modulated beams simultaneously. The modulation units comprise electro-optic modulators for independently modulating the red, green and blue beams generated by the light units. 
     The microminiaturized projection module  50  further has a first mirror  531 , a second mirror  532 , a third mirror  533  and a fourth mirror  534 . The four mirrors form a 2×2 array. The mirrors are made of polymer and driven electromagnetically. In practice, it is not limited to electromagnetical forces. The mirrors can be driven by electromagnetic forces, electrostatic forces, or the combination thereof. 
     The first mirror  531  and the third mirror  533  project the modulated beams from the first modulation unit  521  and the fourth modulation unit  524 , respectively. However, the second mirror  532  projects the modulated beams from the second modulation unit  522  and the third modulation unit  523  at the same time. The fourth mirror  534  projects the modulated beams from the fifth modulation unit  525  and the six modulation unit  526  simultaneously. 
     The beams projected by the mirrors form the image onto the surface  60  according to the corresponding direction signal received from the image processing unit  502 . It is obvious that the corresponding relation between modulation units and mirrors is not one to one. One mirror can project beams from more than one modulation unit. 
     Please refer to  FIG. 12 . It shows a block diagram of the first light unit  511 . The first light unit  511  comprises a red visible laser diode  5111 , a blue visible laser diode  5112 , and a green visible laser emitter  5113 . The second light unit  512 , the third light unit  513 , the fourth light unit  514 , the fifth light unit  515  and the sixth light unit  516  have the same internal structure. No further diagram is needed for illustrating purpose. Meanwhile, the mirrors have the same structure as that in the second embodiment. Description of the mirrors is omitted. 
     Please see  FIG. 13 . It shows how the image is projected onto the surface  60 . The first mirror  531 , the second mirror  532 , the third mirror  533  and the fourth mirror  534  are used to scan one part of the image. When the image is projected, the surface  60  can be divided into four tiles with 2 columns and 2 rows accordingly. Obviously, every tile has the same area. They are a first tile  601 , a second tile  602 , a third tile  603  and a fourth tile  604 . Although the tile has curved surface, there is no overlap of any two tiles. The key feature of the third embodiment is that one tile is scanned by two modulation units. The second tile  602  receives modulated beams from the second mirror  532  and is scanned by the second modulation unit  522  and the third modulation unit  523 . The fourth tile  604  receives modulated beams from the fourth mirror  534  and is scanned by the fifth modulation unit  525  and the six modulation unit  526 . The beams from the second modulation unit  522  and the third modulation unit  523  scan in different directions and so do the beams from the fifth modulation unit  525  and the six modulation unit  526 . Raster pinch effect on the second tile  602  and the fourth tile  604  can be diminished. Of course, the same means can be applied on the first tile  601  and the third tile  603 . It depends on requirement of the image. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.