Patent Publication Number: US-2009224698-A1

Title: Visual staying display and scan method thereof

Description:
This application claims priority of No. 097108260 filed in Taiwan R.O.C. on Mar. 10, 2008 under 35 USC 119, the entire content of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to the LED-associated technology, and more particularly to a visual staying display and a scan method thereof. 
     2. Related Art 
     Recently, due to the progress of the technology, many consumer electronic products have been sequentially developed. In the early age, a light-emitting diode (LED) light bar is designed according to the visual staying principle.  FIG. 1  is a structure diagram showing a conventional LED light bar. Referring to  FIG. 1 , the circuit includes sixteen LEDs D 01  to D 16  and a handle  10 .  FIG. 2  is a schematic illustration showing an internal memory of the conventional LED light bar. As shown in  FIG. 2 , the LED light bar generally has the internal memory for storing to-be-displayed images. In this memory, each column represents lighting information of the first to sixteenth LEDs D 01  to D 16  in one period of time, wherein “1” represents that the LED emits light and “0” represents that the LED does not emit light. For example, the first column represents that the first to third LEDs D 01  to D 03  and the fourteenth to sixteenth LEDs D 14  to D 16  do not emit light, while the fourth to thirteenth LEDs D 04  to D 13  emit light in the zeroth to ninth unit periods of times. 
       FIG. 3  is a schematic illustration showing the displaying of the conventional LED light bar. As shown in  FIG. 3 , when the user grasps the handle and starts to wave the LED light bar, the LEDs D 01  to D 16  start to flicker according to the order stored in the memory. Thus, when the LED light bar is being waved, “GO” will be displayed. However, the image displayed by the LED light bar is typically fixed, if the to-be-displayed image is to be updated, the LED light bar has to be connected to a computer inevitably to update the internal memory so that the displayed pattern can be changed. However, the user may feel inconvenient in using the LED light bar. 
     The prior art has to update the displayed pattern via the computer. Thereafter, Nippon Optical Ltd. has disclosed a scan-type LED light bar.  FIG. 4A  is a circuit diagram disclosed in China Patent Publication No. N1728197. As shown in  FIG. 4A , the circuit mainly utilizes one multiplexer  41  to select one of the LEDs, such as D 01 , for receiving, and the other multiplexer  42  to select the corresponding LED D 02  to make it emit light. When the sensing starts, a capacitor  43  is charged and a node  44  has a ground voltage.  FIG. 4B  shows operation waveforms in China Patent Publication No. N1728197. As shown in  FIG. 4B , the horizontal axis represents the time, and the vertical axis represents a voltage at a node  45 . During scanning, the position corresponding to the first LED D 01  is black, and the capacitor  43  is discharged via the first LED D 01  at the higher rate. Thus, the balance voltage at the node  45  is higher. When the position corresponding to the first LED D 01  is white, the capacitor  43  is discharged via the first LED D 01  at the lower rate. Thus, the balance voltage at the node  45  is lower. 
     However, this configuration has to divide the time into a plurality of time sectors according to the order of the LEDs D 01  to D 16  when scanning each column, and then the corresponding LEDs are respectively selected using the multiplexers  41  and  42  in each corresponding time sector so that the voltage at the node  45  is sensed. Thus, when the LED light bar is scanning and the LED light bar is moved quicker, the sensing tends to fail. In addition, this technique uses two multiplexers  41  and  42 , two LED driving circuits and two light detecting circuits. If the quick scan has to be reached, the quicker microprocessor is needed to execute the procedure of progressive scan. In addition, the lighting operations have to be respectively performed according to the order of the LEDs D 01  to D 16  during displaying. In order to keep the lighting brightness, the required current during displaying is relatively high. 
     SUMMARY OF THE INVENTION 
     It is therefore an objective of the present invention to provide a visual staying display capable of decreasing the design complexity and decreasing the current flowing through the LED. 
     Another objective of the present invention is to provide a scan method for increasing the scan speed. 
     To achieve the above-identified or other objectives, the present invention provides a visual staying display having a bar-like casing. The visual staying display includes a rear end portion, a front end portion and a microprocessor. A plurality of first LEDs and a plurality of second LEDs are disposed on the front end portion. The first LEDs and the second LEDs are interlacedly arranged in one row. The microprocessor is coupled to the first LEDs and the second LEDs. When a pattern is being scanned, the microprocessor drives the first LEDs to emit light and determines image data on a corresponding position of the second LEDs according to a variation of terminal voltages of the second LEDs with respect to time in each of preset periods. 
     The visual staying display according to the preferred embodiment of the present invention further includes a memory for storing the image data, a button for controlling an operation of the display and a wobble sensor for detecting a wobble frequency of the visual staying display. 
     The present invention provides a scan method. The method includes the steps of: providing a plurality of first LEDs and a plurality of second LEDs, wherein the first LEDs and the second LEDs are interlacedly arranged in one row; and driving the first LEDs to emit light, and determining image data on a corresponding position of the second LEDs according to a variation of terminal voltages of the second LEDs with respect to time in each of preset periods. 
     In the scan method according to the preferred embodiment of the present invention, the steps of driving the first LEDs to emit light and determining the image data on the corresponding position of the second LEDs according to the variation of the terminal voltages of the second LEDs with respect to time comprise: providing a first common cathode pin coupled to cathodes of the first LEDs; providing a second common cathode pin coupled to cathodes of the second LEDs; providing a plurality of first control pins respectively coupled to anodes of the first LEDs; providing a plurality of second control pins respectively coupled to anodes of the second LEDs; and when a pattern is being scanned: supplying a ground voltage to the first common cathode pin; controlling the first control pins to supply a supply voltage to the anodes of the first LEDs; setting the second common cathode pin to a first predetermined voltage; supplying the ground voltage for the second control pins for the preset period, and then setting the second control pins to a high impedance state; and determining the image data of the second LEDs on the corresponding position according to a time when voltages of the anodes of the second LEDs reach a second predetermined voltage. 
     In the scan method according to the preferred embodiment of the present invention, the steps of driving the first LEDs to emit light and determining the image data on the corresponding position of the second LEDs according to the variation of the terminal voltages of the second LEDs with respect to time comprise: providing a first common anode pin coupled to anodes of the first LEDs; providing a second common anode pin coupled to anodes of the second LEDs; providing a plurality of first control pins respectively coupled to cathodes of the first LEDs; providing a plurality of second control pins respectively coupled to cathodes of the second LEDs; and when a pattern is being scanned: supplying a supply voltage to the first common anode pin; controlling the first control pins to supply a ground voltage to the cathodes of the first LEDs; setting the second common anode pin to a first predetermined voltage; supplying the supply voltage to the second control pins for the preset period and then setting the second control pins to a high impedance state; and determining the image data of the second LEDs on the corresponding position according to a time when voltages of the cathodes of the second LEDs reach a second predetermined voltage. 
     The spirit of the present invention is to utilize at least two sets of LEDs interlaced arranged in one row, wherein one set of the LEDs emits light during scanning, and the other set of LEDs scans the image. In addition, as for the LED for detection and its corresponding LED for emitting the light, more than one set of corresponding LEDs can be simultaneously turned on at the same time instant of scanning. Thus, the scan speed is higher than that of the prior art. In the circuit design, it is unnecessary to utilize the multiplexer to select the LEDs, and the system design can be simplified. In addition, the parallel output is adopted, so no additional driving circuit is needed to enhance the brightness. Thus, the cost can be reduced. 
     Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention. 
         FIG. 1  is a structure diagram showing a conventional LED light bar. 
         FIG. 2  is a schematic illustration showing an internal memory of the conventional LED light bar. 
         FIG. 3  is a schematic illustration showing the displaying of the conventional LED light bar. 
         FIG. 4A  is a circuit diagram disclosed in China Patent Publication No. N1728197. 
         FIG. 4B  shows operation waveforms in China Patent Publication No. N1728197. 
         FIG. 5A  is a structure diagram showing a visual staying display according to an embodiment of the present invention. 
         FIG. 5B  is a circuit diagram showing the visual staying display according to the embodiment of the present invention. 
         FIG. 6  is a flow chart showing a scan method according to the embodiment of the present invention. 
         FIG. 7  is a schematic illustration showing the scan principle of the LED according to the embodiment of the present invention. 
         FIG. 8  shows waveforms at an anode of the LED D 81  according to the embodiment of the present invention. 
         FIG. 9  shows the common anode control adopted in the LED of this embodiment different from the embodiment of  FIG. 5B . 
         FIG. 10  is a schematic illustration showing the scan principle of the LED according to the embodiment of the present invention. 
         FIG. 11  shows waveforms at an anode of the LED D 101  according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
       FIG. 5A  is a structure diagram showing a visual staying display according to an embodiment of the present invention.  FIG. 5B  is a circuit diagram showing the visual staying display according to the embodiment of the present invention. Referring to  FIG. 5A , the display has a bar-like casing. The display includes a rear end portion  501  and a front end portion  502 . The rear end portion is to be handled by the user, for example. A plurality of LEDs D 501  to D 516  is disposed on the front end portion. Next, as shown in  FIG. 5B , the LEDs D 501  to D 516  are divided into two sets, which are respectively odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515 , and even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516 . The cathodes of the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are coupled to a first common cathode pin N 01  of a microprocessor  503 , while the cathodes of the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  are coupled to a second common cathode pin N 02  of the microprocessor  503 . The anodes of the LEDs D 501  to D 516  are coupled to control pins C 01  to C 16  of the microprocessor  503  via resistors R, respectively. One of ordinary skill in the art should understand that R is a current-limiting resistor, and is not an essential element. So, detailed descriptions thereof will be omitted. 
     When a pattern is to be displayed, as shown in  FIGS. 2 and 3 , the corresponding LEDs are simultaneously lighted up in each of preset periods. For example, the fourth to twelfth LEDs D 504  to D 512  are lighted up at the time instant T 1 , the third to fourteenth LEDs D 503  to D 514  are lighted up at the time instant T 2 , and so on, wherein the detailed descriptions thereof will be omitted. 
       FIG. 6  is a flow chart showing a scan method according to the embodiment of the present invention. Referring to  FIGS. 5B and 6 , the scan method includes the following steps. 
     In step S 601 , the method starts. 
     In step S 602 , a plurality of first LEDs and a plurality of second LEDs are provided, wherein the first LEDs and the second LEDs are interlacedly arranged in one row. In  FIG. 5B , the LEDs D 501  to D 516  are divided into the odd-numbered sets of LEDs and the even-numbered sets of LEDs, which are interlacedly arranged. 
     In step S 603 , in each first preset period, the first LED is driven to emit light, and image data on a corresponding position of the second LEDs is determined according to a variation of terminal voltages of the second LEDs with respect to time. When the user starts to scan the image using the visual staying display, the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are lighted up. The second common cathode pin N 02  is charged to a supply voltage Vdd of an integrated circuit before the scanning starts.  FIG. 7  is a schematic illustration showing the scan principle of the LED according to the embodiment of the present invention.  FIG. 8  shows waveforms at an anode of the LED D 81  according to the embodiment of the present invention. Referring to  FIGS. 7 and 8 , the LED D 81  may be regarded as one of the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  in  FIG. 5B . When the scanning starts, the cathode of the LED D 81  is charged to Vdd, and the anode of the LED D 81  is discharged to the ground voltage GND in advance so that it is kept at the high impedance state. 
     Next, when the LED D 81  has scanned the image, the LEDs on two sides thereof emit light to illuminate the to-be-scanned image. The cathode of the LED D 81  charges the anode of the LED D 81  according to the brightness of the scanned image (i.e., according to the received brightness). When the LED D 81  is being manufactured, a stray capacitance Cx is formed. Thus, the voltage at the anode of the LED D 81  is increased with time during scanning. Herein, the microprocessor  503  may detect a time when the voltage at the anode of the LED for receiving the image reaches a predetermined voltage via the control pins C 01  to C 16 , or may detect the voltage at the anode of the LED for receiving the image via the control pins C 01  to C 16  in a certain preset period to determine the brightness of the image. 
     The waveform  801  corresponds to the voltage at the anode of the LED D 81  when the scanned image is brighter; and the waveform  802  corresponds to the voltage at the anode of the LED D 81  when the scanned image is darker. That is, when the scanned image is darker, the image absorbs the light generated by the LEDs adjacent to the LED D 81  so that the light received by the LED D 81  is less. Thus, the current flowing from the cathode of the LED D 81  to the anode of the LED D 81  is lower, so the voltage rise is slower. Correspondingly, when the scanned image is brighter, the image reflects the light generated by the LED adjacent to the LED D 81  so that the light received by the LED D 81  is more. The current flowing from the cathode of the LED D 81  to the anode of the LED D 81  is also higher, so the voltage rise is quicker. Thus, the brightness of the image can be easily judged. 
     In step S 604 , in each second preset period, the second LED is driven to emit light, and image data on a corresponding position of the first LEDs is determined according to a variation of terminal voltages of the first LEDs with respect to time. In the second preset period, the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  becomes the light source and the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are for detecting the image. In addition, the first preset period and the second preset period are interlacedly and repeatedly arranged. Therefore, the captured image will become clearer and the resolution of the captured image can be raised. Since the image captured concept in the embodiment of the present invention is described in step S 603 , so, the detailed descriptions thereof is omitted. 
     Although one aspect of the present invention is disclosed hereinabove, one of ordinary skill in the art should understand that the target voltage for charging the LED D 81  does not have to be the supply voltage Vdd of the integrated circuit after he or she has realized the embodiment of the invention, and that the voltage may be determined according to the design. In addition, a capacitor may also be coupled between the anode of the LED D 81  and the ground voltage in addition to the stray capacitance Cx. In addition, the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are lighted up, and the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  are for detecting the image and then the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  are lighted up, and the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are for detecting the image in this embodiment. However, one of ordinary skill in the art should understand that the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  are used for the light source, and the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are only used for detecting the image. Alternatively, the odd-numbered sets of LEDs D 501 , D 503 , D 505 , D 507 , D 509 , D 511 , D 513  and D 515  are only used for the light source, and the even-numbered sets of LEDs D 502 , D 504 , D 506 , D 508 , D 510 , D 512 , D 514  and D 516  are only used for detecting the image without departing from spirit of the present invention. So, detailed descriptions thereof will be omitted. 
     Next, one embodiment will be described to make one of ordinary skill in the art easily understand the spirit of the present invention. 
       FIG. 9  shows the common anode control adopted in the LED of this embodiment different from the embodiment of  FIG. 5B . Referring to  FIG. 9 , the circuit includes a button  901 , a memory  902 , a microprocessor  903 , LEDs D 901  to D 916  and a wobble sensor  904 . The button may be used to control an operation of the visual staying display to start lighting or entering the scan mode, for example. The memory  902  stores the to-be-displayed image data or the scanned image data. The wobble sensor  904  is mainly adopted to detect the wobble frequency of the visual staying display. The microprocessor  903  may correct the lighting times of the LEDs D 901  to D 916  according to the wobble frequency detected by the wobble sensor  904 . 
     The difference between the embodiments of  FIGS. 9 and 5B  is that the LED of this embodiment of  FIG. 9  adopts the common anode control. The anodes of the odd-numbered sets of LEDs D 901 , D 903 , D 905 , D 907 , D 909 , D 911 , D 913  and D 915  are coupled to a first common anode pin P 01  of the microprocessor  903 , while the anodes of the even-numbered sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  are coupled to a second common anode pin P 02  of the microprocessor  903 . 
     During scanning, the odd-numbered sets of LEDs D 901 , D 903 , D 905 , D 907 , D 909 , D 911 , D 913  and D 915  start to emit light, while the anodes of the even-numbered sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  are set to the ground voltage. In addition, the cathodes of the even-numbered sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  are pre-charged to the supply voltage VDD, and are then set to the high impedance state. After the even-numbered sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  receive the light, the cathodes thereof discharge the anode thereof. Thus, as long as the time when the cathodes of the even-numbered sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  reach the predetermined voltage is detected, or the voltages at the cathodes of several sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  are detected in a predetermined time, the image data on the corresponding position may be obtained. 
       FIG. 10  is a schematic illustration showing the scan principle of the LED according to the embodiment of the present invention.  FIG. 11  shows waveforms at an anode of the LED D 101  according to the embodiment of the present invention. As shown in  FIGS. 10 and 11 , the LED D 101  may be regarded as any one of the even-numbered sets of LEDs D 902 , D 904 , D 906 , D 908 , D 910 , D 912 , D 914  and D 916  of  FIG. 9 . When the scanning starts, the cathode of the LED D 101  is discharged to the ground voltage GND, and the anode of the LED D 101  is pre-charged to the supply voltage Vdd so that the LED D 101  is kept at the high impedance state. 
     Next, when the LED D 101  scans the image, the LEDs on two sides thereof emit light to illuminate the to-be-scanned image. The cathode of the LED D 101  charges the anode thereof according to the brightness of the scanned image (i.e., the received brightness). Because the LED D 101  has the stray capacitance Cx during the manufacturing process, the voltage of the cathode of the LED D 101  is increased with time during scanning. Herein, the microprocessor  903  may detect the time when the voltage at the anode of the LED for receiving the image reaches a predetermined voltage via the control pins C 01  to C 16 , or may detect the voltage at the anode of the LED for receiving the image via the control pins C 01  to C 16  in a certain preset period to determine the brightness of the image. 
     The waveform  1001  corresponds to the voltage at the cathode of the LED D 101  when the scanned image is brighter; and the waveform  1002  corresponds to the voltage at the cathode of the LED D 101  when the scanned image is darker. That is, when the scanned image is darker, the image absorbs the light generated by the LEDs adjacent to the LED D 101  so that the light received by the LED D 101  is less. Thus, the current flowing from the anode of the LED D 101  to the cathode of the LED D 101  is also lower, and the voltage drop is slower. Correspondingly, when the scanned image is brighter, the image reflects the light generated by the LEDs adjacent to the LED D 101  so that the light received by the LED D 101  is more. Thus, the current flowing from the anode of the LED D 101  to the cathode of the LED D 101  is also higher, so the voltage drop is quicker. Thus, the brightness of the image may be easily judged. 
     In summary, the spirit of the present invention is to utilize at least two sets of LEDs interlaced arranged in one row, wherein one set of the LEDs emits light during scanning, and the other set of LEDs scans the image. In addition, as for the LED for detection and its corresponding LED for emitting the light, more than one set of corresponding LEDs can be simultaneously turned on at the same time instant of scanning. Thus, the scan speed is higher than that of the prior art. In the circuit design, it is unnecessary to utilize the multiplexer to select the LEDs, and the system design can be simplified. In addition, the parallel output is adopted, so no additional driving circuit is needed to enhance the brightness. Thus, the cost can be reduced. 
     While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications.