JP2015092204A - Image display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display system with a light pen which allows for entering characters and pictures from a display screen and pointing at a specific location on the image display screen from a distance.SOLUTION: An image display system 100 with a light pen 50 having a photosensitive element 52 for detecting luminescence of an image display device 30 and a drawing switch 51 includes; a coordinate computation circuit 56 which computes coordinates of a position pointed by the light pen 50 on a display screen of the image display device 30 based on output of the photosensitive element 52; and a drawing circuit 46 which generates an image signal for displaying a cursor based on the position coordinates computed by the coordinate computation circuit 56. The drawing circuit 46 generates an image signal for displaying a trajectory of the cursor by storing past position coordinates when the drawing switch 51 is turned on, and generates an image signal for displaying the cursor by not storing past position coordinates when the drawing switch 51 is turned off.

Description

  The present invention relates to an image display system capable of handwritten input using a light pen.

  A typical AC surface discharge type plasma display panel (hereinafter abbreviated as “panel”) as an image display device includes a front substrate on which a plurality of display electrode pairs each composed of a pair of scan electrodes and sustain electrodes are formed, The rear substrate on which the data electrodes are formed is arranged oppositely, and a large number of discharge cells are formed therebetween. Then, ultraviolet rays are generated by gas discharge in the discharge cell, and the phosphors of red, green and blue colors are excited and emitted by the ultraviolet rays to perform color display.

  As a method for driving the panel, a subfield method in which one field period is composed of a plurality of subfields and gradation display is performed by a combination of subfields to emit light is generally used. Each subfield has an initialization period, an address period, and a sustain period. In the initialization period, an initialization discharge is generated, and an initialization operation for forming wall charges necessary for the subsequent address operation is performed. In the address period, address discharge is selectively generated in the discharge cells in accordance with the image to be displayed to form wall charges. In the sustain period, a sustain pulse is alternately applied to the scan electrode and the sustain electrode to generate a sustain discharge, and the phosphor layer of the corresponding discharge cell is caused to emit light, thereby displaying an image.

  In recent years, an application as an electronic blackboard that can input characters and pictures from a display screen, such as a blackboard or a whiteboard, using such a panel has been studied. For example, Patent Document 1 divides one field period into a plurality of subfields, sets the light emission time in each subfield to a different value to enable gradation display, and provides an abscissa detection subfield. There is described an image display device that displays an abscissa detection pattern within a subfield period, detects light emission of the abscissa detection subfield with a light pen, and obtains the abscissa indicated by the light pen from the light emission timing.

  In Patent Document 2, a coordinate detection period is provided in one field only at the time of coordinate detection, and a drive signal for display position detection is output to the scan driver and data driver within this period, and the coordinates are displayed on the plasma display panel. A method is described in which a detection light signal is generated and a position coordinate is detected at a timing at which a light pen light signal is detected.

JP 50-108838 A JP 2001-318765 A

  In the image display system, in addition to a function as an electronic blackboard using a light pen, for example, a pointer that points to a part of the screen is required when giving a presentation. However, it is cumbersome to change the light pen and the pointer for use, and the convenience for the user is impaired.

  The present invention has been made in view of the above problems, and is an image including a light pen that can input characters and pictures from the display screen and can point to a specific position on the image display screen from a remote position. An object is to provide a display system.

  In order to achieve the above object, the present invention is an image display system including an image display device, a light pen having a light receiving element that detects light emission of the image display device, and a drawing switch, and an image indicated by the light pen A coordinate calculation circuit that calculates position coordinates on the display screen of the display device based on the output of the light receiving element; and a drawing circuit that generates an image signal for displaying a cursor based on the position coordinates calculated by the coordinate calculation circuit. When the drawing switch is on, the circuit saves the past position coordinates and creates an image signal that displays the locus of the cursor. When the drawing switch is off, the circuit moves the cursor without saving the past position coordinates. An image signal to be displayed is created. With this configuration, it is possible to provide an image display system including a light pen that can input characters and pictures from the display screen and can point to a specific position on the image display screen from a remote position.

  According to the present invention, it is possible to provide an image display system including a light pen that can input characters and pictures from the display screen and can point to a specific position on the image display screen from a remote position. It becomes.

It is a disassembled perspective view of the panel used for the image display system in embodiment of this invention. It is an electrode array figure of the panel used for the image display system. It is a drive voltage waveform figure applied to the panel of the image display system. It is a drive voltage waveform figure applied to the panel of the image display system. It is a circuit block diagram of the image display system. It is a timing chart of the coordinate detection subfield of the image display system. It is a schematic diagram explaining the position coordinate detection method of the image display system. It is a block diagram of the filter circuit of the image display system. It is a schematic diagram which shows an example of drawing of the image display system. It is a schematic diagram which shows an example of drawing of the image display system.

  Hereinafter, an image display system according to an embodiment of the present invention will be described using an example in which a plasma display panel is used as an image display device with reference to the drawings.

(Embodiment)
FIG. 1 is an exploded perspective view of panel 10 used in the image display system according to the embodiment of the present invention. On the glass front substrate 11, a plurality of display electrode pairs 14 made up of scanning electrodes 12 and sustaining electrodes 13 are formed. A dielectric layer 15 is formed so as to cover the display electrode pair 14, and a protective layer 16 is formed on the dielectric layer 15. A plurality of data electrodes 22 are formed on the rear substrate 21, a dielectric layer 23 is formed so as to cover the data electrodes 22, and a grid-like partition wall 24 is formed thereon. A phosphor layer 25 that emits red, green, and blue light is provided on the side surface of the partition wall 24 and on the dielectric layer 23.

  The front substrate 11 and the rear substrate 21 are arranged to face each other so that the display electrode pair 14 and the data electrode 22 intersect with each other with a minute discharge space interposed therebetween, and the outer periphery thereof is sealed with a sealing material such as glass frit. Has been. In the discharge space, for example, a mixed gas of neon and xenon is sealed as a discharge gas. The discharge space is partitioned into a plurality of sections by barrier ribs 24, and discharge cells are formed at portions where display electrode pairs 14 and data electrodes 22 intersect. These discharge cells discharge and emit light to display an image.

  Note that the structure of the panel 10 is not limited to the above-described structure, and for example, the panel 10 may include a stripe-shaped partition wall.

  FIG. 2 is an electrode array diagram of panel 10 used in the image display system according to the embodiment of the present invention. The panel 10 includes n scan electrodes SC1 to SCn (scan electrode 12 in FIG. 1) and n sustain electrodes SU1 to SUn (sustain electrode 13 in FIG. 1) extending in the first direction. The m data electrodes D1 to Dm (data electrode 22 in FIG. 1) extending in the second direction intersecting with the first direction are arranged. A discharge cell is formed at a portion where one pair of scan electrode SCi (i = 1 to n) and sustain electrode SUi intersects one data electrode Dj (j = 1 to m), and the discharge cell is in the discharge space. M × n are formed. Here, the three discharge cells formed at the intersection of the three adjacent data electrodes and the pair of display electrodes are a red pixel, a green pixel, and a blue pixel. Then, a red pixel, a green pixel, and a blue pixel constitute one pixel as a set. Therefore, for example, if the panel 10 is a high definition panel having 1080 × 1920 pixels, n = 1080 and m = 1920 × 3 = 5760. Hereinafter, for convenience, the first direction is referred to as a row direction, and the second direction is referred to as a column direction.

  Next, the drive voltage waveform of the image display apparatus will be described. In the present embodiment, one field period is composed of a plurality of image display subfields for displaying an image and a plurality of coordinate detection subfields for detecting coordinates.

  First, details of the image display subfield will be described. The image display subfield includes a plurality of subfields having a predetermined luminance weight, and displays an image by controlling light emission / non-light emission of each image display subfield for each discharge cell.

  In the present embodiment, the image display subfield is eight subfields SF1 to SF8 having an initialization period, an address period, and a sustain period. The luminance weights of the subfields SF1 to SF8 are, for example, (1, 34). 21, 13, 8, 5, 3, 2). Then, in the initializing period of the subfield SF1 arranged first, a forced initializing operation for forcibly generating initializing discharge is performed regardless of the previous discharge history. In the initializing period of subfields SF2 to SF8, a selective initializing operation is performed in which an initializing discharge is generated only in the discharge cells that have generated a discharge in the immediately preceding subfield. However, the subfield configuration such as the number of subfields and the luminance weight is not limited to the above.

  FIG. 3 is a drive voltage waveform diagram applied to the panel of the image display system in the embodiment of the present invention, and shows drive voltage waveforms applied to each electrode of panel 10 in subfields SF1 to SF3.

  In the first half of the initialization period Pia of the subfield SF1, the voltage 0 (V) is applied to the data electrodes D1 to Dm, and the voltage 0 (V) is applied to the sustain electrodes SU1 to SUn. An upward ramp voltage that rises from voltage Vi1 to positive voltage Vi2 is applied to scan electrodes SC1 to SCn. Then, weak initializing discharge occurs between scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, and scan electrodes SC1 to SCn and data electrodes D1 to Dm, respectively. Negative wall voltage is accumulated on scan electrodes SC1 to SCn, and positive wall voltage is accumulated on data electrodes D1 to Dm and sustain electrodes SU1 to SUn. Here, the wall voltage on the electrode represents a voltage generated by wall charges accumulated on the dielectric layer covering the electrode, the protective layer, the phosphor layer, and the like. In this way, variations in the wall voltage depending on the discharge history of each discharge cell are eliminated, and an initializing discharge that matches the wall voltage of each discharge cell is generated.

  In the second half of the initialization period Pia, the voltage 0 (V) is applied to the data electrodes D1 to Dm, and the positive voltage Ve is applied to the sustain electrodes SU1 to SUn. A downward ramp voltage that falls from voltage 0 (V) to negative voltage Vi4 is applied to scan electrodes SC1 to SCn. During this time, weak initialization discharges occur between scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, and between scan electrodes SC1 to SCn and data electrodes D1 to Dm. Then, the wall voltage on scan electrodes SC1 to SCn and the wall voltage on sustain electrodes SU1 to SUn are weakened, and the positive wall voltage on data electrodes D1 to Dm is adjusted to a value suitable for the write operation. Thus, the initialization period Pia forcibly performing the initialization discharge ends.

  In the subsequent address period Pw, the voltage 0 (V) is applied to the data electrodes D1 to Dm, the voltage Ve is applied to the sustain electrodes SU1 to SUn, and the voltage Vc is applied to each of the scan electrodes SC1 to SCn.

  Next, a scan pulse of negative voltage Va is applied to scan electrode SC1 in the first row. Then, an address pulse of a positive voltage Vd is applied to the data electrode Dk (k = 1 to m) of the discharge cell that should emit light in the first row among the data electrodes D1 to Dm. Then, the voltage difference at the intersection between the data electrode Dk and the scan electrode SC1 of the discharge cell to which the address pulse is applied exceeds the discharge start voltage, and between the data electrode Dk and the scan electrode SC1, and between the sustain electrode SU1 and the scan electrode SC1. Address discharge occurs between A positive wall voltage is accumulated on scan electrode SC1, a negative wall voltage is accumulated on sustain electrode SU1, and a negative wall voltage is also accumulated on data electrode Dk. In this manner, an address operation is performed in which an address discharge is caused in the discharge cells to be lit in the first row and wall voltage is accumulated on each electrode. On the other hand, the voltage at the intersection between the data electrode to which the address pulse is not applied and the scan electrode SC1 does not exceed the discharge start voltage, so that address discharge does not occur.

  Next, a scan pulse of voltage Va is applied to scan electrode SC2 in the second row. Then, an address pulse of the voltage Vd is applied to the data electrode Dk of the discharge cell that should emit light in the second row among the data electrodes D1 to Dm. Then, address discharge occurs in the discharge cell to which the address pulse is applied.

  Similarly, scan pulses are sequentially applied to scan electrodes SC3 to SCn and address pulses are applied to data electrodes Dk of the discharge cells to be lit to sequentially write in the discharge cells to be lit in the third to nth rows. Generate a discharge. Thus, the writing period Pw ends.

  In the subsequent sustain period Ps, the voltage 0 (V) is applied to the data electrodes D1 to Dm. A sustain pulse of positive voltage Vs is applied to scan electrodes SC1 to SCn, and voltage 0 (V) is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the address discharge has occurred, a sustain discharge occurs between scan electrode SCi and sustain electrode SUi, and phosphor layer 25 emits light due to the ultraviolet rays generated at this time. Then, negative wall voltage is accumulated on scan electrode SCi, and positive wall voltage is accumulated on sustain electrode SUi. Further, a positive wall voltage is also accumulated on the data electrode Dk. In the discharge cells in which no address discharge has occurred in the address period Pw, no sustain discharge occurs, and the wall voltage at the end of the initialization period Pia is maintained.

  Subsequently, voltage 0 (V) is applied to scan electrodes SC1 to SCn, and a sustain pulse of voltage Vs is applied to sustain electrodes SU1 to SUn. Then, the sustain discharge occurs again in the discharge cell in which the sustain discharge has occurred, the negative wall voltage is accumulated on the sustain electrode SUi, and the positive wall voltage is accumulated on the scan electrode SCi. Similarly, sustain pulses of the number corresponding to the luminance weight are alternately applied to scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, and sustain discharge is continuously generated in the discharge cells that have caused address discharge in address period Pw. Let

  At the end of sustain period Ps, voltage 0 (V) is applied to data electrodes D1 to Dm, voltage 0 (V) is applied to sustain electrodes SU1 to SUn, and voltage 0 (V) is applied to scan electrodes SC1 to SCn. To the positive voltage Vr is applied. Then, a weak erasing discharge occurs between scan electrode SCi that has generated the sustain discharge and sustain electrode SUi. Then, the wall voltage on scan electrode SCi and sustain electrode SUi is weakened while the positive wall voltage on data electrode Dk remains. Thus, sustain period Ps ends.

  In the initialization period Pib of the subfield SF2, the voltage 0 (V) is applied to the data electrodes D1 to Dm, the voltage 0 (V) is applied to the sustain electrodes SU1 to SUn, and the voltage 0 (to the scan electrodes SC1 to SCn). A downward ramp voltage that falls from V) to voltage Vi4 is applied. Then, in the discharge cell that has caused the sustain discharge in the immediately preceding subfield SF1, a weak initializing discharge is generated between scan electrode SCi and data electrode Dk and between scan electrode SCi and sustain electrode SUi. Then, the wall voltage on scan electrode SCi and sustain electrode SUi is weakened, and the positive wall voltage on data electrode Dk is adjusted to a wall voltage suitable for the write operation. On the other hand, no discharge occurs in the discharge cell that did not cause the sustain discharge in the immediately preceding subfield SF1, and the wall voltage at the end of the initialization period Pia of the immediately preceding subfield SF1 is maintained.

  Since the operation in the writing period Pw of the subfield SF2 is the same as the operation in the writing period Pw of the subfield SF1, description thereof is omitted. The operation in subsequent sustain period Ps is similar to the operation in sustain period Ps of subfield SF1 except for the number of sustain pulses. The operations of subfields SF3 to SF8 are the same as those of subfield SF2 except for the number of sustain pulses.

  Next, details of the coordinate detection subfield will be described. The coordinate detection subfield includes a timing detection subfield SFo, a y coordinate detection subfield SFy, and an x coordinate detection subfield SFx. The timing detection subfield SFo is a subfield for detecting the driving timing of the panel, and is provided for synchronization between the light pen and the image display device. The y coordinate detection subfield SFy is a subfield for detecting the y coordinate on the display screen indicated by the light pen. The x-coordinate detection subfield SFx is a subfield for detecting the x-coordinate on the display screen indicated by the light pen.

  FIG. 4 is a waveform diagram of driving voltages applied to the panel of the image display system in the embodiment of the present invention. Each of the panels 10 in the timing detection subfield SFo, the y coordinate detection subfield SFy, and the x coordinate detection subfield SFx. The drive voltage waveform applied to the electrode is shown. A part of the sustain period Ps of the subfield SF8 arranged immediately before the timing detection subfield SFo is also shown.

  Since the operation in the initialization period Pia of the timing detection subfield SFo is the same as the forced initialization operation in the initialization period Pia of the subfield SF1, description thereof is omitted.

  In the write period Pw of the timing detection subfield SFo, first, the voltage 0 (V) is applied to the data electrodes D1 to Dm, the voltage Ve is applied to the sustain electrodes SU1 to SUn, and the voltage Vc is applied to each of the scan electrodes SC1 to SCn. Apply. Thereafter, an address pulse of voltage Vd is applied to data electrodes D1 to Dm, and a scan pulse of voltage Va is applied to scan electrodes SC1 to SCn. Thereafter, an address discharge is generated in all the discharge cells.

  At this time, the address pulse may be applied to the data electrodes D1 to Dm and the scan pulse may be simultaneously applied to the scan electrodes SC1 to SCn to simultaneously generate the address discharge in all the discharge cells. However, in the present embodiment, the address pulse is applied to the data electrodes D1 to Dm and the scan pulse is sequentially applied to each of the plurality of scan electrodes SC1 to SCn to generate the address discharge.

  Then, the state where the discharge is not performed is maintained for a predetermined time To0 from the time to0 when the last address discharge is generated. The predetermined time To0 is set depending on the time interval of the timing detection discharge described later, and is set longer than the time To1, the time To2, and the time To3 described later.

  In the timing detection period Po of the timing detection subfield SFo, at the time to1, all the timing detection pulses of the voltage Vso are applied to the scan electrodes SC1 to SCn and the voltage 0 (V) is applied to the sustain electrodes SU1 to SUn. A timing detection discharge is generated in the discharge cell. Next, at time to2 after time To1 has elapsed from time to1, voltage 0 (V) is applied to scan electrodes SC1 to SCn and a timing detection pulse of voltage Vso is applied to sustain electrodes SU1 to SUn to detect timing again. Generate a discharge. Next, at time to3 after time To2 has elapsed from time to2, a timing detection pulse of voltage Vso is applied to scan electrodes SC1 to SCn, and voltage 0 (V) is applied to sustain electrodes SU1 to SUn. A timing detection discharge is generated. Subsequently, at time to4 after time To3 has elapsed from time to3, the voltage 0 (V) is applied to scan electrodes SC1 to SCn, and the timing detection pulse of voltage Vso is applied to sustain electrodes SU1 to SUn. A detection discharge is generated. In the present embodiment, the time To1, the time To2, and the time To3 are, for example, 40 μs, 20 μs, and 30 μs, respectively. The voltage Vso of the timing detection pulse is the same voltage as the voltage Vs of the sustain pulse. However, this is not always necessary, and any voltage may be used as long as the timing detection discharge is generated.

  At the end of the timing detection period Po, an ascending ramp voltage that rises to the voltage Vr is applied to the scan electrodes SC1 to SCn to generate a weak erase discharge. This completes the operation of the timing detection subfield SFo.

  The operation in the initialization period Pib of the y-coordinate detection subfield SFy performs the same initialization operation as the selective initialization operation in the initialization period Pib of the subfield SF2. However, since the timing detection discharge is generated in all the discharge cells in the immediately preceding timing detection subfield SFo, the initialization discharge is generated in all the discharge cells here.

  In the y coordinate detection period Py of the y coordinate detection subfield SFy, first, the voltage 0 (V) is applied to the data electrodes D1 to Dm, the voltage Ve is applied to the sustain electrodes SU1 to SUn, and the scan electrodes SC1 to SCn are respectively applied. Applies a voltage Vc.

  Next, a positive y-coordinate detection voltage Vdy is applied to the data electrodes D1 to Dm. Then, a y-coordinate detection pulse having a negative voltage Vay is applied to the scan electrode SC1 in the first row. Then, the voltage difference between the data electrodes D1 to Dm of the discharge cells in the first row and the scan electrodes SC1 exceeds the discharge start voltage, and between the data electrodes D1 to Dm and the scan electrodes SC1 and the sustain electrode SU1. A discharge for detecting the y coordinate occurs between the scan electrode SC1. A positive wall voltage is accumulated on scan electrode SC1, a negative wall voltage is accumulated on sustain electrode SU1, and a negative wall voltage is also accumulated on data electrodes D1 to Dm. In this way, the discharge for detecting the y coordinate is simultaneously generated in the first discharge cell, and the first discharge cell row constituted by the first pixel row, that is, the first discharge cell is changed. Emits light.

  Next, with the y-coordinate detection voltage Vdy applied to the data electrodes D1 to Dm, the y-coordinate detection pulse of the voltage Vay is applied to the scan electrode SC2 in the second row. Then, discharge for detecting y-coordinate occurs between data electrodes D1 to Dm and scan electrode SC2, and between sustain electrode SU2 and scan electrode SC2, and the second pixel row, that is, the second discharge cell row. Emits light. Similarly, the y-coordinate detection pulses are sequentially applied to the scan electrodes SC3 to SCn while the y-coordinate detection voltage Vdy is applied to the data electrodes D1 to Dm, so that the third to n-th discharge cell rows emit light sequentially. .

  Thus, in the y coordinate detection period Py, one horizontal line that moves from the upper end to the lower end of the display screen is displayed. Therefore, as will be described later, the y coordinate of the position of the display screen indicated by the light pen can be detected by receiving the light emission of the discharge cell row with the light pen and knowing the timing of the light emission. However, since the moving speed of the horizontal line is very fast, it looks visually as if the entire display screen is slightly brighter. Thus, the y coordinate detection period Py ends.

  The operation in the initialization period Pia of the x-coordinate detection subfield SFx performs the same forced initialization operation as that in the initialization period Pia of the timing detection subfield SFo.

  In the x coordinate detection period Px of the x coordinate detection subfield SFx, the voltage 0 (V) is applied to the data electrodes D1 to Dm, the voltage Ve is applied to the sustain electrodes SU1 to SUn, and the scan electrodes SC1 to SCn are respectively applied to the scan electrodes SC1 to SCn. A voltage Vc is applied.

  Next, a negative x-coordinate detection voltage Vax is applied to scan electrodes SC1 to SCn. Then, an x coordinate detection pulse of a positive voltage Vdx is applied to one of the data electrodes D1 to D3 in the first to third columns corresponding to one pixel, that is, a red pixel, a green pixel, and a blue pixel. Then, the voltage difference between the data electrodes D1 to D3 of the discharge cells in the first column to the third column and the scan electrodes SC1 to SCn exceeds the discharge start voltage, and the data electrodes D1 to D3 and the scan electrodes SC1 to SCn. And discharge for detecting the x coordinate occurs between sustain electrodes SU1 to SUn and scan electrodes SC1 to SCn. Then, positive wall voltage is accumulated on scan electrodes SC1 to SCn, negative wall voltage is accumulated on sustain electrodes SU1 to SUn, and negative wall voltage is also accumulated on data electrodes D1 to D3. The In this way, discharge for x-coordinate detection is simultaneously caused in the discharge cells in the first column to the third column, and the first column composed of the first pixel column, that is, the first discharge cell. The second discharge cell column composed of the discharge cell column, the second discharge cell, and the third discharge cell column composed of the third discharge cell emit light.

  Next, with the x coordinate detection voltage Vax being applied to the scan electrodes SC1 to SCn, the x coordinate detection pulse of the voltage Vdx is applied to the data electrodes D4 to D6 in the fourth column to the sixth column. Then, discharge for detecting the x coordinate occurs between the data electrodes D4 to D6 and the scan electrodes SC1 to SCn and between the sustain electrodes SU1 to SUn and the scan electrodes SC1 to SCn. The sixth to sixth discharge cell columns emit light.

  In the same manner, the x coordinate detection pulse is sequentially applied to each of the three data electrodes until reaching the data electrode Dm, and light is emitted in sequence until the discharge cell row reaches the m-th discharge cell row for every three discharge cell rows.

  Thus, in the x-coordinate detection period Px, one vertical line that moves from the left end to the right end of the display screen is displayed. Therefore, as will be described later, the x coordinate of the position of the display screen indicated by the light pen can be detected by receiving the light emission of the discharge cell array with the light pen and knowing the timing of the light emission. However, since the moving speed of the vertical line is very fast, it looks visually as if the entire display screen is slightly brighter. Thus, the x coordinate detection period Px ends.

  In this embodiment, the voltage value applied to each electrode is, for example, voltage Vi1 = 150 (V), voltage Vi2 = 350 (V), voltage Vi4 = −175 (V), voltage Va = voltage Vay = voltage Vax. = −200 (V), voltage Vc = −50 (V), voltage Vs = voltage Vso = 205 (V), voltage Vr = 205 (V), voltage Ve = 155 (V), voltage Vd = voltage Vdy = voltage Vdx = 55 (V).

  As described above, in the present embodiment, the voltage Va, the voltage Vay, and the voltage Vax are set to be equal, and the voltage Vd, the voltage Vdy, and the voltage Vdx are set to be equal because of the configuration of the drive circuit. Further, the slope of the rising ramp voltage applied to the scan electrode in the initialization period Pia of the subfield SF1 is 1.5 (V / μs), and the slope of the descending ramp voltage applied to the scan electrode in the initialization periods Pia and Pib is −2.5 (V / μs), the gradient of the rising ramp voltage applied to the scan electrode at the end of the sustain period Ps is 10 (V / μs). However, these voltage values and gradients of the gradient voltage are merely examples, and it is desirable to set them to optimum values as appropriate in accordance with the characteristics of the panel 10 and the specifications of the image display device.

  Next, the configuration of the image display system will be described. FIG. 5 is a circuit block diagram of image display system 100 in the embodiment of the present invention. The image display system 100 includes an image display device 30, a drawing device 40, and a light pen 50.

  The image display device 30 is necessary for the panel 10, the image signal processing circuit 31, the data electrode drive circuit 32, the scan electrode drive circuit 33, the sustain electrode drive circuit 34, the timing generation circuit 35, and each circuit block. And a power supply circuit (not shown) for supplying power.

  The image signal processing circuit 31 switches or synthesizes the input image signal and the drawing signal output from the drawing device 40, and converts them into image data indicating light emission / non-light emission for each subfield. The data electrode drive circuit 32 converts the image data into address pulses corresponding to the data electrodes D1 to Dm and applies them to the data electrodes D1 to Dm.

  The timing generation circuit 35 generates various timing signals for controlling the operation of each circuit block based on the horizontal and vertical synchronization signals, and supplies them to the respective circuit blocks. Scan electrode drive circuit 33 applies a drive voltage to each of scan electrodes SC1 to SCn based on the timing signal, and sustain electrode drive circuit 34 applies a drive voltage to sustain electrodes SU1 to SUn based on the timing signal.

  The light pen 50 is for inputting characters and pictures from the display screen of the panel 10, and includes a drawing switch 51, a light receiving element 52, a timing detection circuit 54, a coordinate calculation circuit 56, and a transmission circuit 58. And.

  The drawing switch 51 is attached to the tip of the light pen 50 and turns on when the light pen 50 is in contact with the display screen of the panel 10 and turns off when the light pen 50 is away from the display screen. The light receiving element 52 receives light emitted from the panel 10 and outputs a light reception signal to the timing detection circuit 54 and the coordinate calculation circuit 56.

  FIG. 6 is a timing chart of the coordinate detection subfield of the image display system 100 according to the embodiment of the present invention, and shows a light reception signal output from the light receiving element 52.

  The timing detection circuit 54 detects light emission generated at a time interval corresponding to a predetermined number sequence determined in advance from the received light signal, and specifies the timing detection discharge in the timing detection period Po of the timing detection subfield SFo. Specifically, four consecutive light emission intervals in which the light emission intervals are time To1, time To2, and time To3 are searched from the received light signal. Then, based on one of four consecutive light emission, for example, light emission generated at time to1 of the timing detection period Po, a rising edge at time ty0 and time tx0 based on the time Toy and the time Tox that are known in advance. Is generated and output to the coordinate calculation circuit 56.

  The coordinate calculation circuit 56 includes a counter for measuring the length of time and an arithmetic circuit that performs an operation on the output of the counter. Then, the position coordinates on the display screen 10 of the image display device 30 indicated by the light pen 50 are calculated based on the output of the light receiving element 52.

  FIG. 7 is a schematic diagram for explaining a coordinate calculation method of the image display system 100 according to the embodiment of the present invention.

  Since the linear light emission extending in the first direction in the y coordinate detection period Py of the y coordinate detection subfield SFy is moved in the second direction, on the display screen of the panel 10, as shown in FIG. A horizontal line Ly moving from the upper end to the lower end of the display screen is displayed. Then, at the time tyy when the horizontal line Ly passes the coordinates (x, y) of the display screen indicated by the light pen 50, the light receiving element of the light pen 50 receives the light emission of the horizontal line Ly. For this reason, the light receiving element outputs a light receiving signal indicating light reception at time tyy as shown in FIG.

  Further, since the linear light emission extending in the second direction is moved in the first direction in the x-coordinate detection period Px of the x-coordinate detection subfield SFx, the display screen of the panel 10 is shown in FIG. Thus, one vertical line Lx that moves from the left end to the right end of the display screen is displayed. At time txx when the vertical line Lx passes the coordinates (x, y) of the display screen indicated by the light pen 50, the light receiving element of the light pen 50 receives the light emission of the vertical line Lx. Therefore, the light receiving element outputs a light receiving signal indicating light reception at time txx as shown in FIG.

  The coordinate calculation circuit 56 measures a time Tyy from time ty0 to time tyy based on the coordinate reference signal output from the timing detection circuit 54 and the light reception signal output from the light receiving element 52 in the y coordinate detection period Py. Then, the y coordinate Y is obtained by dividing the time Tyy by the time Ty1. Further, based on the coordinate reference signal output from the timing generation circuit 35 and the light reception signal output from the light receiving element of the light pen 50 in the x coordinate detection period Px, a time Txx from time tx0 to time txx is measured. Then, the time Txx is divided by the time Tx1 to obtain the x coordinate X. In this way, the coordinate calculation circuit 56 obtains the coordinates (X, Y) of the display screen indicated by the light pen 50.

  The transmission circuit 58 encodes the x-coordinate X and y-coordinate Y calculated by the coordinate calculation circuit 56 and transmits them to the drawing apparatus 40 with a wireless signal. At the same time, the state S of the drawing switch 51 (for example, S = “1” if the drawing switch 51 is on, S = “0” if the drawing switch 51 is off) is encoded and transmitted to the drawing apparatus 40 by a wireless signal. To do.

  The drawing device 40 includes a receiving circuit 42, a filter circuit 44, and a drawing circuit 46.

  The receiving circuit 42 decodes the radio signal sent from the light pen 50 to reproduce the x coordinate X, the y coordinate Y, and the state S of the drawing switch 51. Note that the x-coordinate X, the y-coordinate Y, and the state S of the drawing switch 51 are sent to the receiving circuit 42 from time to time for each field. X (t), y coordinate Y (t), and state S (t) of the drawing switch 51 are described.

  The filter circuit 44 performs a filtering process on the position coordinates calculated by the coordinate calculation circuit 56, here, the x-coordinate X (t) and the y-coordinate Y (t) output from the receiving circuit 42. Then, the filtered x-coordinate FX (t) and y-coordinate FY (t) are output to the drawing circuit 46.

  The x and y coordinates calculated by the coordinate calculation circuit 56 include random errors that occur accidentally. This random error is a statistical variation in discharge or quantization noise generated when digitally processing an optical signal. Since the average value is almost “0”, the position coordinates are not greatly deviated. However, this random error causes a problem that even if the light pen is stopped, the detected coordinates fluctuate finely.

  The filter circuit 44 is provided for performing filter processing for suppressing such random errors. When the filtering process is performed, the problem that the detected coordinates fluctuate finely can be solved. Further, in the present embodiment, a low-pass filter that suppresses rapid changes in the x-coordinate X (t) and the y-coordinate Y (t) input to the filter circuit 44 is provided, and the x-coordinate X (t) and the y-coordinate Y (t) And the strength of the filter is controlled depending on the state S (t) of the drawing switch 51. Thereby, the responsiveness of the detected x-coordinate X (t) and y-coordinate Y (t) is improved, and the problem that the drawing cannot catch up with the movement of the light pen is eliminated. In addition, when writing a fine character that includes a fine outline and repeats drawing and moving, it does not feel unwieldy.

  FIG. 8 is a block diagram of filter circuit 44 of image display system 100 in the embodiment of the present invention. The filter circuit 44 includes a coefficient calculation unit 60, an x coordinate filter 70, and a y coordinate filter 80.

  The x coordinate filter 70 is a cyclic IIR filter including a multiplier 72, an adder 74, a delay unit 75, and a multiplier 76. The multiplier 72 multiplies the input x coordinate X (t) by the filter coefficient Kx (t). The adder 74 adds the output {X (t) × Kx (t)} of the multiplier 72 and the output of the multiplier 76, and outputs an x-coordinate FX (t) subjected to filter processing. The delay unit 75 delays the filtered x coordinate FX (t) by one field. The multiplier 76 multiplies the delayed x coordinate FX (t−1) by a coefficient {1-Kx (t)}. In this way, the low-pass filter process having a strength depending on the filter coefficient Kx (t) is applied to the x-coordinate X (t), and the x-coordinate FX (t) is output. Here, the filter coefficient Kx (t) is a coefficient having a value of “0” or more and “1” or less. As the filter coefficient Kx (t) is smaller, stronger filter processing is performed, and the filter coefficient Kx (t) is larger. The filter processing becomes weak. When the filter coefficient Kx (t) becomes “1”, the x coordinate X (t) is output as it is as the x coordinate FX (t) without performing the filtering process.

  The y-coordinate filter 80 is a cyclic IIR filter having a multiplier 82, an adder 84, a delay unit 85, and a multiplier 86, and depends on the filter coefficient Ky (t) like the x-coordinate filter 70. The y-coordinate FY (t) is output by applying the low-pass filter process of the strength to the y-coordinate Y (t). Again, the filter coefficient Ky (t) is a coefficient having a value of “0” or more and “1” or less. As the filter coefficient Ky (t) is smaller, stronger filter processing is performed, and the filter coefficient Ky (t) is larger. The filter processing becomes weak.

  The coefficient calculation unit 60 includes a delay unit 62, a delay unit 64, and a coefficient calculation unit 66. The delay device 62 delays the input x coordinate X (t) by one field and outputs the x coordinate X (t−1). The delay unit 62 delays the input y coordinate Y (t) by one field and outputs the y coordinate Y (t−1).

  The coefficient calculation unit 66 includes the x coordinate X (t), the y coordinate Y (t), the delayed x coordinate X (t−1), the delayed y coordinate Y (t−1), and the state S ( Based on t), filter coefficients Kx (t) and Ky (t) are calculated.

In this embodiment,
Kx (t) = min (Rx (t) · γ (S (t)), 1)
Ky (t) = min (Ry (t) · γ (S (t)), 1)
It is. However, min (a, b) is a function indicating the smaller of “a” and “b”, and the coefficients Rx (t) and Ry (t) are respectively
Rx (t) = αx · {X (t) −X (t−1)} ^ 2 + βx · {Y (t) −Y (t−1)} ^ 2
Ry (t) = αy · {X (t) −X (t−1)} ^ 2 + βy · {Y (t) −Y (t−1)} ^ 2
It is. Here, α and β are predetermined constants. Γ (S (t)) is a coefficient determined depending on the state S (t) of the drawing switch 51,
γ (1) = 1
γ (0) = 2.8
It is.

  As described above, the coefficients Rx (t) and Ry (t) are inputted coordinates (X (t), Y (t)) and coordinates inputted one field before (X (t−1), Y (t− As the difference from 1)), that is, the amount of change in position coordinates increases, it increases. Therefore, the coefficients Rx (t) and Ry (t) increase when the light pen 50 moves fast on the display screen and decrease when the light pen 50 moves slowly. Thus, the coefficients Rx (t) and Ry (t) are coefficients indicating the moving speed of the light pen 50. When the moving speed of the light pen 50 is large, the filter coefficients Kx (t) and Ky (t) are also large. Therefore, the strength of the filter is weak, and when the moving speed of the light pen 50 is small, the filter coefficients Kx (t), Since Ky (t) also decreases, the strength of the filter increases.

  As described above, the filter circuit 44 according to the present embodiment is a coefficient calculator that calculates the filter coefficients Kx and Ky based on the x-coordinate filter 70 and the y-coordinate filter 80 configured by the cyclic IIR filter and the change amount of the position coordinates. A cyclic component of the x-coordinate filter 70 and the y-coordinate filter 80 when the change amount of the position coordinate is small, and a cyclic component of the x-coordinate filter 70 and the y-coordinate filter 80 when the change amount of the position coordinate is large. The filter coefficients Kx and Ky are calculated so as to be larger than the components. Thus, the filter circuit 44 constitutes a low-pass filter that suppresses rapid changes in the input position coordinates (X (t), Y (t)), and the position coordinates (X (t), Y ( The higher the moving speed of t)), the stronger the filtering process is performed.

  As a result, when the light pen 50 is moved slowly, the filter becomes stronger and the random error becomes smaller, and the coordinates (FX (t), FY (t)) subjected to the filter processing may fluctuate finely. Disappear. Further, since the filter becomes weak when the light pen 50 is moved quickly, the response of the filter process becomes fast, and the coordinates (FX (t), FY (t)) subjected to the filter process cannot catch up with the movement of the light pen. There is no fear of that.

  Γ (S (t)) is a coefficient determined depending on the state S (t) of the drawing switch 51, and is a small value when the drawing switch 51 is on, and is large when the drawing switch 51 is off. Value. Therefore, the filter circuit 44 has more cyclic components of the x-coordinate filter 70 and the y-coordinate filter 80 when the drawing switch 51 is on than the cyclic components of the x-coordinate filter 70 and the y-coordinate filter 80 when the drawing switch 51 is off. Thus, filter coefficients Kx and Ky are calculated. Thus, the filter circuit 44 performs stronger filtering when the drawing switch 51 is on than when the drawing switch 51 is off.

  For this reason, the filter becomes stronger during drawing and the random error becomes smaller, and the filter becomes weaker during movement of the light pen and the response is improved. As a result, even when writing fine characters, it is possible to draw with a natural feeling.

  In this embodiment, in order to achieve both suppression of random errors and responsiveness, when the drawing switch 51 is on, the coordinate movement speed is 14 (cm / s) or more, and the drawing switch 51 is off. The filter coefficients Kx (t) and Ky (t) are set to “1” when the coordinate moving speed is 9 (cm / s) or higher, that is, the filter is not effective. However, these values are desirably set optimally depending on the screen size of the image display apparatus.

  The drawing circuit 46 includes a frame memory. When the drawing switch 51 is on, the filtered x-coordinate FX (t) and y-coordinate FY (t) are written in the frame memory. Based on the position coordinates (FX (t), FY (t)) thus filtered by the filter circuit 44, an image signal for displaying the locus of the position coordinates indicated by the light pen 50 when the drawing switch 51 is turned on is created. And output to the image display device 30. When the drawing switch 51 is off, the x coordinate FX (t-1) and the y coordinate FY (t-1) are deleted from the frame memory, and the x coordinate FX (t) and the y coordinate FY (t) are deleted from the frame memory. Write to. In this way, a drawing signal for displaying the cursor indicating the position pointed to by the light pen 50 is created and output to the image display device 30.

  9A and 9B are schematic diagrams illustrating an example of drawing of the image display system 100 according to the embodiment of the present invention. For example, the drawing switch is turned on by bringing the light pen 50 into contact with the image display surface at the position A shown in FIG. 9A. Then, the drawing circuit 46 writes a pattern such as a circle of a predetermined color and size in the frame memory with the pixel corresponding to the coordinates (FX (t), FY (t)) calculated from the filter circuit 44 as the center. . When the user moves the light pen to position B in FIG. 9A while keeping the light pen in contact with the image display surface of panel 10, the coordinates (FX (t), FY (t)) also move. The drawing circuit 46 sequentially writes a predetermined pattern in the frame memory around the moving coordinates (FX (t), FY (t)). In this way, the drawing circuit 46 creates a drawing signal indicating the locus of the light pen 50 as shown in FIG. 9A.

  Further, the light pen 50 is moved away from the image display surface at the position B shown in FIG. 9B to turn off the drawing switch. Even in this case, the coordinates (X (t), Y (t)) can be calculated while the light receiving element 52 receives the light emitted from the panel 10, and the coordinates (FX) are obtained from the filter circuit 44. (T), FY (t)) is output. Then, the drawing circuit 46 writes a pattern of a predetermined color and shape indicating the cursor in the frame memory with the pixel corresponding to the coordinates (FX (t), FY (t)) as the center. When the user moves the light pen 50 away from the panel 10 to the position C in FIG. 9B, the coordinates (FX (t), FY (t)) also move. Then, the drawing circuit 46 deletes the coordinates of the previous field, that is, the coordinates corresponding to the past position coordinates (FX (t−1), FY (t−1)) without saving the coordinates (FX (T), FY (t)) A pattern of a predetermined color and shape indicating the cursor is written in the frame memory with the corresponding pixel as the center. In this way, the drawing circuit 46 creates a drawing signal indicating a cursor that moves the position on the display screen indicated by the light pen 50, as shown in FIG. 9B.

  In this way, the drawing circuit 46 saves the past position coordinates when the drawing switch 51 is on and creates an image signal that displays the locus of the cursor, and when the drawing switch 51 is off, the past position. Create an image signal that displays the cursor without saving the coordinates.

  Thus, the user can input characters, pictures, and the like from the display screen using the light pen 50, and can point to a specific position on the image display screen from a distant position using the same light pen 50. .

  The image signal processing circuit 31 of the image display device 30 converts the image data indicating light emission / non-light emission for each subfield based on the drawing signal output from the drawing device 40. Thereby, the image and the cursor written with the light pen can be displayed on the display screen. Alternatively, the input image signal and the drawing signal output from the drawing device 40 are combined and converted into image data indicating light emission / non-light emission for each subfield. Thereby, the image written with the light pen and the image of the input image signal can be superimposed and displayed.

  Although not described in this embodiment, a coordinate reference signal can also be used as a masking signal for blocking light emission not related to the position coordinates. That is, as shown in FIG. 6, by setting the falling timing of the coordinate reference signal generated by the timing detection circuit 54 to the end time of the y coordinate detection period Py and the end time of the x coordinate detection period Px, The light reception signal may be output to the coordinate calculation circuit 56 only during the period when the coordinate reference signal is “high level”.

  In the present embodiment, the drawing switch 51 is described as being attached only to the tip of the light pen 50. However, a drawing switch may be provided on the side of the light pen 50 so that the user can operate it. . Or you may provide a drawing switch in both the front-end | tip part of the light pen 50, and the side surface of the light pen 50. FIG. As a result, even a position away from the display screen can be drawn. Furthermore, the drawing may be performed with a drawing switch provided at the tip of the light pen 50, and a cursor pointing to one point on the display screen may be displayed with the drawing switch provided on the side surface of the light pen 50.

  In addition, each circuit block described in the embodiment may be configured as an electric circuit, or may be configured using a processor or the like programmed to perform the same operation.

  Furthermore, each specific numerical value used in the embodiment is merely an example, and it is desirable to appropriately set an optimal value according to the characteristics of the panel, the specifications of the image display device, and the like.

  Since the present invention includes a light pen that can input characters and pictures from the display screen and can point to a specific position on the image display screen from a distant position, the plasma display panel, the liquid crystal display panel, and the organic EL The present invention is useful as an image display system capable of handwritten input using a light pen on an image display device using a display panel, an LED panel, or the like.

DESCRIPTION OF SYMBOLS 10 Panel 12 Scan electrode 13 Sustain electrode 22 Data electrode 30 Image display apparatus 31 Image signal processing circuit 32 Data electrode drive circuit 33 Scan electrode drive circuit 34 Sustain electrode drive circuit 35 Timing generation circuit 40 Drawing apparatus 42 Receiving circuit 44 Filter circuit 46 Drawing Circuit 50 Light pen 51 Drawing switch 52 Light receiving element 54 Timing detection circuit 56 Coordinate calculation circuit 58 Transmission circuit 60 Coefficient calculation unit 62, 64, 75, 85 Delay unit 66 Coefficient calculation unit 70 x coordinate filter 72, 76, 82, 86 Multiplication 74, 84 Adder 80 Y coordinate filter 100 Image display system X, Y, FX, FY Coordinate Kx, Ky Filter coefficient

Claims (1)

An image display system comprising: an image display device; and a light pen having a light receiving element that detects light emission of the image display device and a drawing switch;
A coordinate calculation circuit for calculating a position coordinate on the display screen of the image display device indicated by the light pen based on an output of the light receiving element;
A drawing circuit for creating an image signal for displaying a cursor based on the position coordinates calculated by the coordinate calculation circuit;
The drawing circuit saves the past position coordinates when the drawing switch is on to generate an image signal for displaying the locus of the cursor, and when the drawing switch is off, the past position coordinates An image display system for generating an image signal for displaying a cursor without saving the image.

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