Patent Publication Number: US-2023162633-A1

Title: Pov display device and control method therefor

Description:
TECHNICAL FIELD 
     The present disclosure is applicable to a display device-related technical field, and relates, for example, to a POV display device using light emitting diodes (LED), which are semiconductor light emitting elements. 
     BACKGROUND ART 
     In a field of a display technology, display devices having excellent characteristics such as thinness, flexibility, and the like have been developed. On the other hand, currently commercialized major displays are represented by a LCD (liquid crystal display) and an OLED (organic light emitting diode). 
     Recently, there is a POV display device that may reproduce various characters and graphics as well as moving images using an afterimage effect of a human by rotating a light emitting module in which light emitting elements are one-dimensionally arranged, and at the same time, driving the light emitting module at a high speed based on an angle. 
     In general, when continuously observing 24 or more still images for each second, a viewer recognizes the still images as the moving image. A conventional image display device, such as a CRT, the LCD, or a PDP, displays still images of 30 to 60 frames for each second, so that the viewer may recognize the still images as the moving image. In this regard, when continuously observing more still images for each second, the viewer may feel smoother images. As the number of still images displayed for each second decreases, it becomes difficult to smoothly display the images. 
     In a case of rotation type-display, afterimages of a preceding frame and a following frame appear to be in contact with each other resulted from rotation of a panel, and accordingly, a tearing phenomenon in which a screen of the contact portion of both frames is torn in a process of frame conversion occurs. 
     Therefore, a method for solving such tearing phenomenon of the POV display device is required. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure is to provide a POV (Persistence of Vision) display device using light emitting elements that may solve a tearing phenomenon resulted from image output of the POV display device. 
     Technical Solutions 
     As a first aspect for achieving the above object, the present disclosure provides a persistence of vision display device using light emitting elements including a fixed module including a motor, a rotatable module positioned on the fixed module and rotated by the motor, at least one panel coupled to the rotatable module, a plurality of light sources arranged on the panel and constituting a plurality of pixels, a light source module including a light emitting element array having the plurality of light sources arranged in a longitudinal direction, and a controller that generates at least one sub-frame at a location between a first main frame and a second main frame formed by the panel, wherein the first main frame precedes the second main frame in time. 
     In addition, the controller may multiply the first main frame and the second main frame by weights, respectively, during each image scanning duration, and generate the at least one sub-frame by combining the first main frame and the second main frame respectively multiplied by the weights with each other. 
     In addition, the controller may detect a difference between the first main frame and the second main frame, select linear weights as the weights when the difference is equal to or greater than a preset threshold value, and select non-linear weights as the weights when the difference is smaller than the preset threshold value. 
     In addition, the controller may increase the weights in a portion where an amount of change between the first main frame and the second main frame is small when the non-linear weights are selected as the weights. 
     In addition, the controller may, when the panel includes a plurality of panels, divide an image scanning area into areas for the respective panels, and apply the weights to the areas. 
     As a first aspect for achieving the above object, the present disclosure provides a method for controlling a POV display device including inputting image data of a first main frame and a second main frame, detecting weights, applying the weights to the first main frame and the second main frame, respectively, forming a sub-frame by combining the first main frame and the second main frame applied with the weights to each other, and outputting synthesized image data. 
     In addition, the detecting of the weights may include detecting a difference between the first main frame and the second main frame, selecting linear weights as the weights when the difference is equal to or greater than a preset threshold value, and selecting non-linear weights as the weights when the difference is smaller than the preset threshold value. 
     In addition, the selecting of the non-linear weights as the weights may further include pre-processing images of the first main frame and the second main frame, and detecting the weights of the frames based on analysis of the image. 
     In addition, the method may further include, before the inputting of the image data of the first main frame and the second main frame, dividing an image scanning area into areas for respective panels when there are the plurality of panels. 
     Advantageous Effects 
     According to one embodiment of the present disclosure, the problem as described above may be solved. 
     That is, the occurrence of the tearing in the image of the POV display device may be solved. 
     Furthermore, in the present disclosure, there are additional technical effects not mentioned here, and those skilled in the art are able to understand such effects through the entirety of the specification and the drawings. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view showing a POV (Persistence Of Visual) display device according to an embodiment of the present disclosure. 
         FIG.  2    is a diagram showing a conventional image output scheme. 
         FIG.  3    is a diagram showing frames based on a conventional image output scheme. 
         FIG.  4    is a block diagram of a POV display device according to an embodiment of the present disclosure. 
         FIG.  5    is a diagram showing an image output scheme according to an embodiment of the present disclosure. 
         FIG.  6    is a diagram showing frames based on an image output scheme according to an embodiment of the present disclosure. 
         FIG.  7    is a diagram showing a combining scheme in a case in which weights are linearly applied according to an embodiment of the present disclosure. 
         FIG.  8    is a diagram showing a combining scheme in a case in which weights are linearly applied according to an embodiment of the present disclosure. 
         FIG.  9    is a diagram showing a combining scheme in a case in which weights are non-linearly applied according to an embodiment of the present disclosure. 
         FIG.  10    is a flowchart of forming a sub-frame according to an embodiment of the present disclosure. 
         FIG.  11    is a diagram more specifically showing a flowchart of forming a sub-frame according to an embodiment of the present disclosure. 
     
    
    
     BEST MODE 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and redundant description thereof will be omitted. As used herein, the suffixes “module” and “unit” are added or used interchangeably to facilitate preparation of this specification and are not intended to suggest distinct meanings or functions. In describing embodiments disclosed in this specification, relevant well-known technologies may not be described in detail in order not to obscure the subject matter of the embodiments disclosed in this specification. In addition, it should be noted that the accompanying drawings are only for easy understanding of the embodiments disclosed in the present specification, and should not be construed as limiting the technical spirit disclosed in the present specification. 
     Furthermore, although the drawings are separately described for simplicity, embodiments implemented by combining at least two or more drawings are also within the scope of the present disclosure. 
     In addition, when an element such as a layer, region or module is described as being “on” another element, it is to be understood that the element may be directly on the other element or there may be an intermediate element between them. 
     The display device described herein is a concept including all display devices that display information with a unit pixel or a set of unit pixels. Therefore, the display device may be applied not only to finished products but also to parts. For example, a panel corresponding to a part of a digital TV also independently corresponds to the display device in the present specification. The finished products include a mobile phone, a smartphone, a laptop, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, a tablet, an Ultrabook, a digital TV, a desktop computer, and the like. 
     However, it will be readily apparent to those skilled in the art that the configuration according to the embodiments described herein is applicable even to a new product that will be developed later as a display device. 
     In addition, the semiconductor light emitting element mentioned in this specification is a concept including an LED, a micro LED, and the like, and may be used interchangeably therewith. 
       FIG.  1    is a perspective view showing a POV (Persistence of Visual) display device according to an embodiment of the present disclosure. 
       FIG.  1    shows a POV display device in which each light emitting element array (not shown) is disposed on each of fan type-panels  310 ,  320 ,  330 , and  340  in a longitudinal direction of each panel. 
     Although  FIG.  1    shows a cylinder type-POV display device, the present disclosure is also applicable to a fan type-POP display device. 
     Such POV display device may largely include a fixed module  100  including a motor  110 , a rotatable module  200  positioned on this fixed module  100  and rotated by the motor  110 , and a light source module  300  that is coupled to the rotatable module  200 , includes the light emitting element arrays, and displays an afterimage by the rotation so as to implement a display. 
     In this regard, the light source module  300  may include the one or more bar-shaped panels  310 ,  320 ,  330 , and  340  radially disposed from a central point of rotation. However, this is an example, and the light source module  300  may include one or more panels. 
     The light source module  300  may include the light emitting element arrays arranged on the panels  310 ,  320 ,  330 , and  340  in the longitudinal direction, respectively. 
     Each of the panels  310 ,  320 ,  330 , and  340  constituting the light source module  300  may form a printed circuit board (PCB). That is, each of the panels  310 ,  320 ,  330 , and  340  may have a function of the printed circuit board. In each of such panels, each of the light emitting element arrays may implement individual unit pixels and may be disposed in the longitudinal direction of each panel. 
     The panels  310 ,  320 ,  330 , and  340  respectively equipped with such light emitting element arrays may implement the display while rotating using the afterimage. The implementation of the afterimage display will be described in detail below. 
     As such, the light source module  300  may be composed of the panels  310 ,  320 ,  330 , and  340  on which the light emitting element arrays are respectively arranged. 
     That is, multiple light emitting elements (not shown) may be arranged in one direction on each of the panels  310 ,  320 ,  330 , and  340  to constitute pixels so as to constitute each of the light emitting element arrays. In this regard, a light emitting diode (LED) may be used as the light emitting element. 
     On each of the panels  310 ,  320 ,  330 , and  340 , each of the light emitting element arrays on which the light emitting elements are arranged to form individual pixels in one direction and are linearly installed may be disposed. 
     As mentioned above, the light source module  300  may be composed of the multiple panels  310 ,  320 ,  330 , and  340 , but may also be implemented with a single panel including the light emitting element arrays. However, when the light source module  300  is implemented with the multiple panels as in the example in  FIG.  1   , because the multiple panels may implement one frame image in a divided manner, the light source module  300  may rotate at a lower rotation speed than when implementing the image of the same frame. 
     In one example, drivers  314  (see  FIG.  4   ) for driving the light emitting elements may be installed on a rear surface of each of the panels  310 ,  320 ,  330 , and  340  constituting the light source module. 
     As such, the drivers  314  are installed on the rear surface of each of the panels  310 ,  320 ,  330 , and  340 , so that a light emitting surface of each panel may not be disturbed, an effect on lighting of light sources (the light emitting elements) caused by interference or the like may be minimized, and the panels  310 ,  320 ,  330 , and  340  may be constructed with minimal areas. Such panels  310 ,  320 ,  330 , and  340  with the small areas may improve transparency of the display. 
     In one example, a front surface of each of the panels  310 ,  320 ,  330 , and  340  on which each light emitting element array is installed may be treated with a dark color (for example, black) so as to improve a contrast ratio, a color, and the like of the display, thereby maximizing an effect of the light sources. 
     In one example, the fixed module  100  may form frame structures. That is, the fixed module  100  may include multiple frames  101  that are designed to be divided from each other and coupled with each other. 
     Such frame structures may provide a space in which the motor  110  may be installed, and may provide a space in which a power supply  120 , an RF module  126  (see  FIG.  4   ), and the like are installed. 
     In addition, a weight (not shown) may be installed in the fixed module  100  in order to reduce an effect of the high-speed rotation of the rotatable module  200 . 
     Similarly, the rotatable module  200  may form frame structures. That is, the rotatable module  200  may include multiple frames  201  that are designed to be divided from each other and coupled with each other. 
     Such frame structures may provide a space in which a driving circuit  210  for driving the light emitting element arrays to implement the display is installed. 
     In this regard, a driving shaft of the motor  110  may be fixed with a shaft fixing module formed in a lower frame  201  of the rotatable module  200 . As such, the driving shaft of the motor  110  and a center of rotation of the rotatable module  200  may be located on the same axis. 
     In addition, the light source module  300  may be fixedly installed on the frame structures. 
     In one example, power may be transferred between the fixed module  100  and the rotatable module  200  in a wireless power transfer scheme. To this end, a transfer coil  130  for transmitting wireless power may be installed at a top of the fixed module  100 , and a receiving coil  220  located at a position facing the transfer coil  130  may be installed at a bottom of the rotatable module  200 . 
       FIG.  2    is a diagram showing a conventional image output scheme, and  FIG.  3    is a diagram showing frames based on a conventional image output scheme. 
     Conventionally, when converting frames, as shown in  FIG.  2   , a first main frame  401  is converted into a second main frame  402  without a separate sub-frame, so that a screen tearing phenomenon, that is, a tearing phenomenon occurred between the first main frame  401  and the second main frame  402  as shown in  FIG.  3   . 
     When such a tearing phenomenon occurs, there was a problem in that an image is displayed unnaturally because the image is not continuously and naturally converted. 
       FIG.  4    is a block diagram of a POV display device according to an embodiment of the present disclosure that has solved the above problem. 
     Hereinafter, a configuration for driving the POV display device will be briefly described with reference to  FIG.  4   . Such configuration may be equally applied to not only the cylinder type-POV display device shown in  FIG.  1   , but also the fan type-POV display device. 
     First, a driving circuit  120  may be installed in the fixed module  100 . Such driving circuit  120  may include a power supply. The driving circuit  120  may include a wireless power transmitter  121 , a DC-DC converter  122 , and an LDO  123  for supplying individual voltages. 
     External power may be supplied to the driving circuit  120  and the motor  110 . 
     In addition, the fixed module  100  may have an RF module  126 , so that the display may be driven by a signal transmitted from the outside. 
     In one example, the fixed module  100  may have means for sensing the rotation of the rotatable module  200 . An infrared ray may be used as such means for sensing the rotation. Accordingly, an IR emitter  125  may be installed in the fixed module  100 , and an IR receiver  215  may be installed in the rotatable module  200  at a location corresponding to an infrared ray emitted from such IR emitter  125 . 
     In addition, the fixed module  100  may include a controller  124  for controlling the driving circuit  120 , the motor  110 , the IR emitter  125 , and the RF module  126 . 
     In one example, the rotatable module  200  may include a wireless power receiver  211  for receiving a signal from the wireless power transmitter  121 , a DC-DC converter  212 , and an LDO  213  for supplying individual voltages. 
     The rotatable module  200  may have an image processor  216  that processes the image to be realized via the light emitting element arrays using RGB data of the displayed image. A signal processed by the image processor  216  may be transmitted to the driver  314  of the light source module  300  so as to realize the image. 
     In addition, in the rotatable module  200 , a controller  214  for controlling the wireless power receiver  211 , the DC-DC converter  212 , the LDO  213 , the IR receiver  215 , and the image processor  216  may be installed. 
     Such image processor  216  may generate a signal for controlling light emission of the light sources of the light source module  300  based on image data to be output. In this regard, data for the light emission of the light source module  300  may be internal or external data. 
     The data stored internally (in the rotatable module)  200  may be image data stored in advance in a storage device, such as a memory (e.g., a SD card), mounted together in the image processor  216 . The image processor  216  may generate the light emission control signal based on such internal data. 
     The image processor  216  may transmit, to the driver, a signal for controlling image data of a specific frame to be displayed on each light emitting element array after delay. 
     In addition, the image processor  216  may receive the image data from the fixed module  100 . In this regard, the external data may be output via an optical data transmitting device with the same principle as a photo coupler, or a data transmitting device of an RF scheme such as Bluetooth or Wi-Fi. 
     In this regard, as mentioned above, the means for sensing the rotation of the rotatable module  200  may be disposed. That is, as means for recognizing a location (a speed) with respect to the rotation, such as an absolute location and a relative location with respect to the rotation, so as to output light source data suitable for each rotational position (speed) during the rotation of the rotatable module  200 , the IR emitter  125  and the IR receiver  215  may be arranged. In one example, the same function may be implemented via an encoder, a resolver, and a Hall sensor. 
     In one example, data required to drive the display may optically transmit a signal at a low cost using the principle of the photo coupler. That is, when the light emitting elements and light receiving elements are positioned in the fixed module  100  and the rotatable module  200 , the data may be received without interruption even when the rotatable module  200  rotates. In this regard, the IR emitter  125  and the IR receiver  215  described above may be used for such data transmission. 
     As described above, the power may be transferred between the fixed module  100  and the rotatable module  200  using the wireless power transfer (WPT). 
     The power may be supplied without a wire connection using a resonance shape of the wireless power transfer coil. 
     To this end, the wireless power transmitter  121  may convert the power into an RF signal of a specific frequency, and a magnetic field generated by a current flowing through the transfer coil  130  may generate an induced current in the receiving coil  220 . 
     In this regard, a natural frequency of the coil and a transmission frequency at which actual energy is transmitted may be different from each other (a magnetic induction scheme). 
     In one example, resonant frequencies of the transfer coil  130  and the receiving coil  220  may be the same with each other (a self-resonant scheme). 
     The wireless power receiver  211  may convert the RF signal input from the receiving coil  220  into a direct current so as to transmit required power to a load. 
       FIG.  5    is a diagram showing an image output scheme according to an embodiment of the present disclosure, and  FIG.  6    is a diagram showing frames based on an image output scheme according to an embodiment of the present disclosure. 
     As shown in  FIG.  5   , the present disclosure may form and output sub-frames  411 ,  412 , and  413  during the conversion from the first main frame  401  to the second main frame  402 . 
     That is, the image signal processor  216  (see  FIG.  4   ) may form the at least one sub-frame at a location between the first main frame  401  and the second main frame  402  formed by the panels  310 ,  320 ,  330 , and  340 . 
     In this regard, the first main frame  401  temporally precedes the second main frame  402 . 
     In this case, as shown in  FIG.  6   , at a point at which the first main frame  401  and the second main frame  402  meet each other, the images may be continuously and naturally converted without the tearing phenomenon. 
       FIGS.  7  and  8    are diagrams showing a combining scheme in a case in which weights are linearly applied according to an embodiment of the present disclosure, and  FIG.  9    is a diagram showing a combining scheme in a case in which weights are non-linearly applied according to an embodiment of the present disclosure. 
     As shown in  FIGS.  7  to  9   , the sub-frame may be formed by multiplying the first main frame  401  and the second main frame  402  by the weights, respectively, during each image scanning duration, and combining the first main frame  401  and the second main frame  402  to which the weights are applied to each other. 
       FIG.  7    is a diagram showing a scheme for combining the first main frame  401  and the second main frame  402  to each other by applying a linear algorithm in a case in which there is one panel. 
       FIG.  8    is a diagram illustrating a scheme of combining the first main frame  401  and the second main frame  402  to each other by applying the linear algorithm in a case in which there are two or more panels  310 ,  320 ,  330 , and  340 . In this case, after dividing an image scanning area of each frame into areas for respective panels, the respective divided areas of the frames are multiplied by the weights, respectively, and the frames are combined with each other in the same manner as in  FIG.  7   . Four panels  310 ,  320 ,  330 , and  340  are shown in  FIG.  1   , but the number of panels is irrelevant as long as there are two or more panels when using the combining scheme in the case in which there are a plurality of panels in  FIG.  8   . 
     In this regard, the weight may be applied to the first main frame  401  while decreasing from 100% to 0%, and the weight may be applied to the second main frame  402  while increasing from 0% to 100%. 
     In this regard, in terms of the weights, linear weights may be selected when a difference between the first main frame  401  and the second main frame  402  is equal to or greater than a preset threshold value, and non-linear weights may be selected when the difference is smaller than the preset threshold value. 
       FIG.  9    is a diagram showing a scheme of combining the first main frame  401  and the second main frame  402  to each other by applying a non-linear algorithm in the case in which there is one panel. In this regard, the weight may be changed to become great, and be applied to a portion with a small amount of change between the first main frame  401  and the second main frame  402 , such as a background or a still portion. When the non-linear algorithm is applied, a problem of sharpness deterioration by the image combination of the linear algorithm may be compensated. 
     When the non-linear weights are selected, the weight may be increased in the portion in which the amount of change between the first main frame  401  and the second main frame  402  is small. 
     When the non-linear weights are selected, the problem of the sharpness deterioration by the image combination may be compensated than in the case in which the linear weights are selected. 
     In addition, when there are the plurality of panels, the image signal processor  216  may divide the image scanning area into the areas for the respective panels, and apply the weight to each area. 
       FIG.  10    is a flowchart of forming a sub-frame according to an embodiment of the present disclosure. 
     As shown in  FIG.  10   , first, the first and second main frames  401  and  402  are input (s 1101 ), and the weights of the first and second main frames  401  and  402  are detected (s 1102 ). The detected weights are applied to the first and second main frames  401  and  402 , respectively, and the first and second main frames  401  and  402  are combined with each other (s 1103 ) so as to form a first sub-frame  411  (s 1104 ). The first sub-frame  411  thus formed may be output at the location between the first and second main frames  401  and  402   
     The weight may be applied to the first main frame  401  while decreasing from 100% to 0% and the weight may be applied to the second main frame  402  while increasing from 0% to 100% during each image scanning duration. 
     By repeating the processes from s 1101  to s 1105 , n sub-frames may be formed. 
     The first sub-frame  411  temporally precedes second and third sub-frames  412  and  413 , and the second sub-frame  412  temporally precedes the third sub-frame  413 . 
     Although  FIG.  5    shows the first, second, and third sub-frames  411 ,  412 , and  413 , the number of sub-frames is not limited thereto. The number of sub-frames may be equal to or greater than one. 
     In a following image, the second main frame  402  may become the first main frame  401 , and a third main frame (not shown) may become the second main frame  402 . 
       FIG.  11    is a diagram more specifically showing a flowchart of forming a sub-frame according to an embodiment of the present disclosure. 
     As shown in  FIG.  11   , first, the difference between the first main frame  401  and the second main frame  402  is detected, and whether to apply the linear algorithm is determined based on the detected difference value. Specifically, when the detected difference value is equal to or greater than the preset threshold value, the linear weights are applied as the weight, and when the detected difference value is smaller than the preset threshold value, the non-linear weights are applied as the weight (s 1201 ). 
     When the linear weights are applied, an elapsed time within one frame is set to t frame , a period of one frame is set to T, and values of α and β are detected based on Mathematical Equations 1 and 2 below (s 1202 ). 
       α=1−( t   frame   /T )  [Mathematical Equation 1]
 
       β=( t   frame   /T )  [Mathematical Equation 2]
 
     In the present disclosure, there may be one or the plurality of panels. In this regard, the POV display device of the present disclosure is a display that outputs the image by the afterimage. The minimum required number of panels may be determined based on a rotation speed. As the number of panels increases, the rotation speed may be lowered. 
     When the non-linear weights are applied, images of the first main frame  401  and the second main frame are preprocessed (s 1203 ), and the weights of the first and second main frames are detected based on such analysis (s 1204 ). 
     D (before-frame) and D (after-frame) values that are respectively image data of the first main frame  401  and the second main frame  402  are input (s 1205 ), and the detected weights are applied to such image data values and the image data values to which the weights are applied are added together Based on Mathematical Equations 3 to 5 below (s 1206 ). 
       D α =D before-frame X α   [Mathematical Equation 3]
 
       D β =D after-frame X β   [Mathematical Equation 4]
 
         D=D   α   +D   β   [Mathematical Equation 5]
 
     Here, D is image data of the first sub-frame  411  obtained by applying the weights to the image data of the first and second main frames  401  and  402  and then adding the image data to which the weights are applied together. 
     The synthesized image data is output (s 1207 ). 
     The weight may be applied to the first main frame  401  while decreasing from 100% to 0% and the weight may be applied to the second main frame  402  while increasing from 0% to 100% during each image scanning duration. 
     By repeating the processes from s 1201  to s 1207 , n sub-frames may be formed. 
     Although  FIG.  5    shows the first, second, and third sub-frames  411 ,  412 , and  413 , the number of sub-frames is not limited thereto. The number of sub-frames may be equal to or greater than one. 
     In the following image, the second main frame  402  may become the first main frame  401 , and the third main frame (not shown) may become the second main frame  402 . 
     As such, in the present disclosure, the POV display device may solve the occurrence of the phenomenon in which the screen is torn in the process of the frame conversion, that is, the tearing phenomenon by synthetizing and outputting the sub-frame to which the weights of the first main frame  401  and the second main frame  402  based on the image scanning duration are applied between the first main frame  401  and the second main frame  402 . 
     The above description is merely illustrative of the technical idea of the present disclosure. Those of ordinary skill in the art to which the present disclosure pertains will be able to make various modifications and variations without departing from the essential characteristics of the present disclosure. 
     Therefore, embodiments disclosed in the present disclosure are not intended to limit the technical idea of the present disclosure, but to describe, and the scope of the technical idea of the present disclosure is not limited by such embodiments. 
     The scope of protection of the present disclosure should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.