Patent Publication Number: US-7586503-B2

Title: Reducing acoustical noise in differently aiming sub-frames of image data frame

Description:
BACKGROUND 
   Some types of display devices, such as projectors, employ light modulators like digital micromirror devices (DMD&#39;s) to modulate light in accordance with image data. A light modulator like a DMD has a given resolution of pixel areas, and generally the resolution of the display device itself matches the resolution of the DMD or other light modulator that it uses. However, more recently a technique has been introduced in which the resolution of the display device is increased beyond the resolution of its DMD or other light modulator. 
   For instance, a mirror or lens may be moved back and forth to direct the light modulated by the DMD or other light modulator in different directions, so that a given pixel area of the DMD or other light modulator can be used for more than one pixel of the display device. The patent application entitled “Image Display System and Method,” filed on Sep. 11, 2002, and published as U.S. patent application publication no. 2004/0027363, describes such an approach to increasing the resolution of a display device over that of its DMD or other light modulator. However, the back-and-forth movement of the mirror or lens can cause undesired acoustical noise. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings referenced herein form a part of the specification. Features shown in the drawing are meant as illustrative of only some embodiments of the invention, and not of all embodiments of the invention, unless otherwise explicitly indicated, and implications to the contrary are otherwise not to be made. 
       FIG. 1  is a diagram of the general approach by which a modulator having a given resolution can be employed to yield the display of image data with a greater resolution by using a physically adjustable aiming mechanism, according to an embodiment of the invention. 
       FIG. 2  is a diagram of a frame of image data divided into two sub-frames, according to an embodiment of the invention. 
       FIG. 3  is a diagram depicting the waveform of a signal for controlling the physical adjustment of an aiming mechanism, which causes acoustical noise in the physical adjustment of the aiming mechanism, according to an embodiment of the invention. 
       FIG. 4  is a diagram depicting the waveform of a signal for controlling the physical adjustment of an aiming mechanism, which causes little acoustical noise in the physical adjustment of the aiming mechanism but decreases image quality, according to an embodiment of the invention. 
       FIG. 5  is a diagram depicting the waveform of a signal for controlling the physical adjustment of an aiming mechanism, which reduces acoustical noise in the physical adjustment of the aiming mechanism with little decrease in image quality, according to an embodiment of the invention. 
       FIG. 6  is a diagram depicting the waveform of a signal for controlling the physical adjustment of an aiming mechanism, which reduces acoustical noise in the physical adjustment of the aiming mechanism with little decrease in image quality, according to another embodiment of the invention. 
       FIGS. 7A and 7B  are diagrams of an aiming sub-system having an aiming mechanism that is physically adjustable, according to different embodiments of the invention. 
       FIG. 8  is a block diagram of a rudimentary display device, such as a projector, according to an embodiment of the invention. 
       FIG. 9  is a flowchart of a method for using a modulator having a given resolution to display image data with a greater resolution by using a physical adjustable aiming mechanism, according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
   In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, electrical, electro-optical, software/firmware and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     FIG. 1  shows a general approach  100  by which a light modulator  104  having a given resolution can be employed to yield the display of image data with a greater resolution, according to an embodiment of the invention. The approach  100  is exemplarily described in relation to a single pixel area  106  of the modulator  104 . However, the approach  100  is the same for all the pixels of the modulator  104 . Furthermore, the approach  100  may be that which is more particularly described in the patent application entitled “Image Display System and Method,” filed on Sep. 11, 2002, and published as U.S. patent application publication no. 2004/0027363. 
   Light is directed towards the modulator  104 , as indicated by the arrow  102 . The modulator  104  may be a digital micromirror device (DMD), or another type of light modulator. The pixel area  106  of the modulator  104  specifically modulates the light in accordance with either a first pixel or a second pixel of image data. The pixel area  106  may correspond to an individual micromirror within a DMD, for instance. The light as modulated by the pixel area  106  is directed towards an aiming mechanism  110 , as indicated by the arrow  108 . The aiming mechanism  110  may be or include a mirror, a lens, a refractive plate of refractory glass, or another type of aiming mechanism. The aiming mechanism  110  is able to move back and forth, as indicated by the arrows  112 . That is, the aiming mechanism  110  is able to be physically adjusted. As depicted in  FIG. 1 , the aiming mechanism  110  is reflective, but can also be refractive. That is, the aiming mechanism  110  may be a reflective aiming mechanism, or a refractive aiming mechanism. The aiming mechanism  110  may alternatively be referred to as an image shifter, or an image-shifting mechanism. 
   When the pixel area  106  has modulated the light in accordance with the first pixel of the image data, the aiming mechanism  110  directs the light to the position  118 A, as indicated by the arrow  114 . When the pixel area  106  has modulated the light in accordance with the second pixel of the image data, the aiming mechanism  110  directs the light to the position  118 B, as indicated by the arrow  114 . The positions  118 A and  118 B, collectively referred to as the positions  118 , are depicted in  FIG. 1  as being adjacent positions, but in other embodiments may be non-adjacent, or may be overlapping. 
   Physically adjusting the aiming mechanism  110  depending on the pixel of the image data in accordance with which the pixel area  106  of the modulator  104  is currently modulating the light allows the pixel area  106  to be used for more than one pixel of the image data. With respect to all the pixel areas of the modulator  104 , this approach  100  allows for the display of image data with greater resolution than the number of pixel areas of the modulator  104  itself. The approach  100  has been described in relation to the pixel area  106  being able to be used for two pixels. However, in other embodiments, the approach  100  may be used so that each pixel area of the modulator  104  can be used for more than two pixels. 
   Furthermore, the pixel area  106  may modulate the light in accordance with elements of the image data other than individual pixels. For instance, the pixel area  106  may modulate the light in accordance with a first sub-pixel of a given pixel, and then modulate the light in accordance with a second sub-pixel of the same pixel. In such an embodiment, the aiming mechanism  110  may direct the light as modulated by the pixel area  106  in accordance with the first sub-pixel to the position  118 A, and direct the light as modulated by the pixel area  106  in accordance with the second sub-pixel to the position  118 B. 
     FIG. 2  shows a representative frame  200  of image data that can be used in conjunction with the approach  100  of  FIG. 1 , according to an embodiment of the invention. The frame  200  is divided into a first sub-frame  202 A and a second sub-frame  202 B, collectively referred to as the sub-frames  202 . The sub-frame  202 A may in one embodiment contain half of the pixels of the image data, and the sub-frame  202 B may contain the other half of the pixels of the image data. In another embodiment, the sub-frame  202 A may contain half of the sub-pixels of all the pixels of the image data, and the sub-frame  202 B may contain the other half of the sub-pixels of all the pixels of the image data. 
   With respect to the positions  118  and the pixel area  106  in  FIG. 1 , the sub-frame  202 A contains the part of the image data that the pixel area  106  modulates light in accordance therewith while the aiming mechanism  110  is directing this light onto the position  118 A, as indicated by the arrow  114 . Similarly, the sub-frame  202 B contains the part of the image data that the pixel area  106  modulates light in accordance therewith while the aiming mechanism is directing this light onto the position  118 B, as indicated by the arrow  116 . Thus, by dividing each frame of the image data into sub-frames, the modulator  104  modulates light in accordance with the different sub-frames as the aiming mechanism  110  directs this modulated light to different positions. 
   Physically adjusting the aiming mechanism  110  to move the aiming mechanism  110  so that it directs light to different positions can be accomplished by using an actuator, which may be part of the aiming mechanism  110 , that is responsive to a signal.  FIG. 3  shows an example of a signal  300  that can be used to physically adjust the aiming mechanism  110 , according to an embodiment of the invention. The signal  300  has a square wave waveform. The square wave waveform of the signal  300  provides for the best picture quality in using the modulator  104  to display image data with a greater resolution than the number of pixel areas of the modulator  104 . 
   The low portion  302  of the waveform corresponds to the aiming mechanism  110  being moved such that it directs modulated light to one position, while the high portion  304  of the waveform corresponds to the aiming mechanism  110  being moved such that it directs modulated light to another position. For example, the low portion  302  may correspond to the aiming mechanism  110  directing light modulated by the pixel area  106  to the position  118 A in  FIG. 1 . The high portion  304  may correspond to the aiming mechanism  110  directing light modulated by the pixel area  106  to the position  118 B in  FIG. 1 . 
   The transition  306  between the low portion  302  and the high portion  304  of the waveform of the signal  300  is at a ninety-degree angle, and thus is representative of an impulse function. The transition  306  between the low and high portions  302  and  304  is instantaneous, and therefore is necessarily faster than the slew rate of the aiming mechanism  110 . That is, the transition  306  is faster than the maximum rate at which the aiming mechanism  110  can be physically adjusted to move such that it directs light at the position  118 B in  FIG. 1  instead of the light at the position  118 A in  FIG. 1 , and vice-versa. Having the transition greater than the slew rate of the aiming mechanism  110  results in acoustical noise when physically adjusting the aiming mechanism  110 , because the aiming mechanism  110  is attempting to move faster than it is capable of moving. 
   The corners of the waveform of the signal  300 , such as the corner  308 , are sharp square corners. Having sharp and/or square corners within the waveform of the signal  300  also results in acoustical noise when physically adjusting the aiming mechanism  110 . This is because the sharp and/or square corners of the waveform represent high-frequency energy that reveal itself as acoustical noise as the aiming mechanism  110  is being moved. Thus, while the waveform of the signal  300  provides for optimal image quality, it also provides for a large amount of acoustical noise when physically adjusting the aiming mechanism  110 . 
     FIG. 4  shows an example of another signal  400  that can be used to physically adjust the aiming mechanism  110 , according to an embodiment of the invention. The signal  400  has an approximate sine wave waveform. The approximate sine wave waveform of the signal  400  provides for a small amount of acoustical noise in using the modulator  104  to display image data with a greater resolution than the number of pixel areas of the modulator  104 . This is because the transition  406  between the low portion  402  and the high portion  404  of the waveform is less than the slew rate of the aiming mechanism  110 , and also because there are no corners within the waveform of the signal  400 . 
   However, the waveform of the signal  400  provides for less than optimal image quality. This is because the signal  400  does not result in the aiming mechanism  110  directing modulated light to any given position for any great length of time. For instance, the low portion  402  is reached for only a brief moment in time, before the signal  400  begins the transition  406  upwards to the high portion  404 . Therefore, in the context of  FIG. 1 , the aiming mechanism  110  directs the light modulated by the pixel area  106  to the position  118 A for just a correspondingly brief moment in time, which tends to blur the image being displayed. 
   Similarly, the high portion  404  is reached for only a brief moment in time, also tending to blur the image being displayed, before the signal  400  begins a transition downwards again. Therefore, in the context of  FIG. 1 , the aiming mechanism  110  directs the light modulated by the pixel area  106  to the position  118 B for just a correspondingly brief moment in time. That is, the waveform of the signal  400  is such that most of the time the aiming mechanism  110  is being physically adjusted and thus moving, such that the aiming mechanism  110  does not direct light at any given position for any great length of time. 
     FIG. 5  shows an example of another signal  500  that can be used to physically adjust the aiming mechanism  110 , according to an embodiment of the invention. The waveform of the signal  500  provides a compromise between acoustical noise and image quality. In particular, the waveform of the signal  500  reduces the acoustical noise as compared to the waveform of the signal  300  of  FIG. 3 , while providing for nearly the same image quality as that of the waveform of the signal  300 . 
   The waveform of the signal  500  has a low portion  502  and a high portion  504  that are maintained for relatively great lengths of time. Thus, the aiming mechanism  110  directs light to given positions for correspondingly great lengths of time, ensuring good image quality. That is, the waveform of the signal  500  is such that a good percentage of the time the aiming mechanism  110  is not being physically adjusted and not moving. For example, the low portion  502  may correspond to the aiming mechanism  110  directing modulated light by the pixel area  106  to the position  118 A in  FIG. 1 , whereas the high portion  504  may correspond to the aiming mechanism  110  directing modulated light by the pixel area  106  to the position  118 B in  FIG. 1 . 
   Acoustical noise in physically adjusting the aiming mechanism  110  in accordance with the signal  500  is reduced via two features of the waveform of the signal  500 . First, the slope of the transition  506  between the low portion  502  and the high portion  504  of the waveform matches the slew rate of the aiming mechanism  110 . As a result, the aiming mechanism  110  is not attempted to be moved, or physically adjusted, faster than it can be intrinsically moved, in contradistinction to the waveform of the signal  300  of  FIG. 3 . Having the transition  506  match the slew rate of the aiming mechanism  110  therefore reduces the noise when physically adjusting the aiming mechanism  110 . 
   Second, corners of the waveform, such as the corner  508 , are smoothed, or rounded. The smoothed, or rounded, corners of the waveform decrease the amount of high-frequency energy that reveals itself as acoustical noise. Because the waveform has less high-frequency energy, there is less of such energy to reveal itself as acoustical noise, which also reduces the noise when physically adjusting the aiming mechanism  110 . 
     FIG. 6  shows an example of another signal  550  that can be used to physically adjust the aiming mechanism  110 , according to an embodiment of the invention. The waveform of the signal  550 , like that of the signal  500  of  FIG. 5 , provides a compromise between acoustical noise and image quality. The waveform of the signal  550  reduces the acoustical noise as compared to the waveform of the signal  300  of  FIG. 3 , while providing for nearly the same image quality as that of the waveform of the signal  300 . 
   The waveform of the signal  550  has a low portion  552  and a high portion  554  that are maintained for relatively great lengths of time. Thus, the aiming mechanism  110  directs light to given positions for correspondingly great lengths of time, ensuring good image quality, as has been described in relation to the signal  500  of  FIG. 5 . That is, the waveform of the signal  550  is such that a good percentage of the time the aiming mechanism  110  is not being physically adjusted and not moving. 
   Acoustical noise in physically adjusting the aiming mechanism  110  in accordance with the signal  550  is reduced via two features of the waveform of the signal  550 . First, the slope of the transition  556  between the low portion  552  and the high portion  554  of the waveform matches the slew rate of the aiming mechanism  110 . Thus, acoustical noise is reduced in the same way as has been described in relation to  FIG. 5 , in which the slope of the transition  506  of the waveform of the signal  500  of  FIG. 5  matches the slew rate of the aiming mechanism  110 . 
   Second, corners of the waveform, such as the corner  558 , are cut off, such as a straight line cut off as is specifically depicted in  FIG. 6 . The cut-off corners decrease the amount of high-frequency energy that reveals itself as acoustical noise. Because the waveform has less high-frequency energy, there is less of such energy to reveal itself as acoustical noise, which also reduces the noise when physically adjusting the aiming mechanism  110 . 
   In general, then, reducing acoustical noise when physically adjusting the aiming mechanism  110  is achieved in at least one of two ways. First, the transitions between low portions and high portions of the waveform of the signal driving the aiming mechanism  110  are to have slopes that are no greater than the slew rate of the aiming mechanism  110 , and can indeed match the slew rate of the aiming mechanism  110 . Second, the corners of the waveform of this signal are softened, such as by smoothing, rounding, or cutting off the corners. 
     FIGS. 7A and 7B  show an aiming sub-system  600 , according to different embodiments of the invention. In both  FIGS. 7A and 7B , the aiming sub-system  600  includes a controller  602  and the aiming mechanism  110 . As has been described, the aiming mechanism  110  differently aims light modulated in accordance with each sub-frame of each frame of image data to a different position. The aiming mechanism  110  may be a mirror and/or a lens. 
   The controller  602  physically adjusts the aiming mechanism  110  such that acoustical noise is reduced. For example, in one embodiment, the controller  602  physically adjusts the aiming mechanism  110  in accordance with the signal  500  of  FIG. 5  that has been described. The controller  602  may be implemented in software, hardware, or a combination of software and hardware. As can be appreciated by those of ordinary skill within the art, the controller  602  and/or the sub-system  600  may include components in addition to and/or in lieu of those depicted in  FIGS. 7A and 7B . For instance, there may be an amplifier to amplify the signal  500  for controlling the aiming mechanism  110 , which may be a part of the controller  602  or a part separate from the controller  602 . 
   In  FIG. 7A , the controller  602  includes a signal generator  604 . The signal generator  604  in  FIG. 7A  specifically generates the signal that controls physical adjustment of the aiming mechanism  110  such that acoustical noise is reduced. For instance, the signal generator  604  in  FIG. 7A  may generate the signal  500  of  FIG. 5  that has been described. 
   In  FIG. 7B , the controller  602  includes a signal modifier  606  in additional to the signal generator  604 . The signal generator  604  in  FIG. 7B  generates a signal for controlling physical adjustment of the aiming mechanism  110 . However, the signal is first passed through the signal modifier  606 , which modifies the signal to reduce acoustical noise when physically adjusting the aiming mechanism  110 . 
   For example, the signal generator  604  in  FIG. 7B  may generate the signal  300  of  FIG. 3  that has been described. The signal modifier  606  may then modify the signal  300  so that it results in the signal  500  of  FIG. 5 . That is, the signal modifier  606  softens the corners of the waveform of the signal  300 , and decreases the slope of the transition of the signal  300 . The signal modifier  606  may be an analog filter, or a digital signal processor (DSP) in varying embodiments of the invention. In both  FIGS. 7A and 7B , the aiming sub-system  600  may include components in addition to those that are depicted and that have been described. 
     FIG. 8  shows a rudimentary display device  700 , according to an embodiment of the invention. The display device  700  may be a front or rear projector, for instance. The display device  700  includes the aiming sub-system  600  and the modulator  104  that have been described, where the aiming sub-system  600  includes the controller  602  and the aiming mechanism  110 . As can be appreciated by those of ordinary skill within the art, the display device  700  may include components in addition to those depicted in  FIG. 8 . 
     FIG. 9  shows a method  800  for achieving a greater resolution in displaying image data than the resolution of the modulator  104 , according to an embodiment of the invention. For each sub-frame of each frame of image data, the modulator  104  is controlled in accordance with the sub-frame ( 802 ). The aiming mechanism  110  is physically adjusted to differently aim the display of each sub-frame to a different position, while reducing acoustical noise ( 804 ). 
   The physical adjustment of the aiming mechanism  110  in  804  may be accomplished in one of at least two different ways. First, a signal may be provided in accordance with which the aiming mechanism  110  is physically adjusted and that has a waveform corresponding to reduced acoustical noise ( 806 ). For instance, the signal that is provided in  806  may be the signal  500  of  FIG. 5 . That is, a signal may be provided in which corners of the waveform thereof are smoothed, and the transition between low and high portions of the waveform at least substantially matches the slew rate of the aiming mechanism  110 . Performing  806  can correspond to the embodiment of  FIG. 7A . 
   Second, a signal may be provided in accordance with which the aiming mechanism  110  is physically adjusted ( 808 ), and then the signal may be modified to reduce acoustical noise when the aiming mechanism  110  is physically adjusted in accordance therewith ( 810 ). For instance, the signal that is provided in  808  may be the signal  300  of  FIG. 3 , which is then modified in  810  to result in the signal  500  of  FIG. 5 . That is, the corners of the waveform of the signal  300  are smoothed, and the transitions between low and high portions of the waveform are adjusted to at least substantially match the slew rate of the aiming mechanism  110 . The modification of the signal in  810  may be accomplished by filtering the signal in an analog manner or by processing the signal in a digital manner. Performing  808  and  810  can correspond to the embodiment of  FIG. 7B . 
   It is noted that, although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and equivalents thereof.