JP2007047918A - Position detector, and liquid crystal display device provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detector for stably detecting a position selected by a position instruction device, and a liquid crystal display device using it. <P>SOLUTION: This position detector 30 comprises a sensor part 300 including a plurality of coil sensors Xn and Ym aligned in a planar form and a selection circuit 304 successively selecting the plurality of coil sensors Xn and Ym, an oscillator 322 generating an output signal inputted to a coil sensor Xn, Ym selected by the selection circuit 304, at least one amplifier 328 adjusting the intensity of the output signal of the oscillator 322, and a switching circuit 326 switching a first route r1 for inputting the output signal of the oscillator 322 as it is to the coil sensor Xn, Ym and a second route r2 for inputting the output signal of the oscillator 322 to the coil sensor Xn, Ym through an adjustment means 328 according to the alignment position of the coil sensor Xn, Ym selected by the selection circuit 304. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a position detection device that detects a position selected by a position indicating device or the like, and a liquid crystal display device including the position detection device.

  In recent years, with the rapid growth of communication devices, lifestyles that exchange information while moving outdoors have become widespread. Accordingly, a tablet personal computer (hereinafter referred to as a tablet PC), which is one of mobile computing, has attracted attention.

  Generally, a flat display device used for this type of tablet PC includes a liquid crystal display panel as a flat display panel. A surface light source device that illuminates the liquid crystal display panel is disposed on the back side of the liquid crystal display panel so as to face the surface. The liquid crystal display panel and the surface light source device are stacked and accommodated in a frame, and the periphery is held by a bezel cover attached from above the liquid crystal display panel. The liquid crystal display device further includes a position detection device incorporated on the back side of the surface light source device.

  This position detection device has, for example, a sensor unit provided with a plurality of coil sensors. The position detection device sequentially selects a plurality of coil sensors arranged in parallel in the position detection direction on the plane, and emits radio waves (for example, a magnetic field, an electric field, or an electromagnetic field) from the coil sensors. On the other hand, when the resonance circuit provided in the position indicating device that indicates the position of any of the plurality of coil sensors resonates, the position detection device receives the resonance output via the corresponding coil sensor. Then, the position detecting device obtains the coordinate value of the position selected by the position indicating device from the distribution of the received signal intensity.

  At this time, the signal level supplied to the coil sensor had the same intensity at all plane positions. For this reason, an error may occur in the position detection result at a position affected by external noise (for example, noise generated by a liquid crystal display device or the like and having a frequency close to the use frequency of the position detection device).

  In particular, when a bezel cover formed of metal is attached, the intensity of the radio wave used for position detection is weak at the outer peripheral portion of the liquid crystal display device. As a result, an error may occur in position detection at the outer periphery of the screen.

2. Description of the Related Art Conventionally, a position pointing device has been developed that performs transmission and reception of radio waves between a coil sensor and a position pointing device at least twice so that an error due to noise as described above does not occur. (See Patent Document 1)
JP 2003-67124 A

  However, in the above position detection device, it is not considered that the intensity of the radio wave is weak at the outer periphery of the screen, and the same processing is performed for all the coil sensors.

  The present invention has been made in view of the above problems, and reduces the position detection result error due to noise or the like, particularly the error in the outer peripheral portion of the liquid crystal display device, and the position selected by the position pointing device. It is an object of the present invention to provide a position detection device that stably detects a light source and a liquid crystal display device using the same.

  The position detection device according to the first aspect of the present invention is selected by the selection unit including a sensor unit including a plurality of coil sensors arranged in a plane and a selection unit that sequentially selects the plurality of coil sensors. An oscillator for generating an output signal input to the coil sensor, at least one adjusting means for adjusting the intensity of the output signal of the oscillator, a first path for directly inputting the output signal of the oscillator to the coil sensor, Switching means for switching the second path for inputting the output signal of the oscillator to the coil sensor via the adjusting means according to the arrangement location of the coil sensor selected by the selection circuit.

  The liquid crystal display device according to the second aspect of the present invention includes a liquid crystal display panel in which a plurality of display pixels are arranged in a matrix, a surface light source device disposed on the back surface of the liquid crystal display panel, and the surface light source device. A position detection device disposed on the back surface, and a bezel cover for holding the periphery of the liquid crystal display panel and the surface light source device, the position detection device, a plurality of coil sensors arranged in a plane, A selection unit that sequentially selects the plurality of coil sensors; an oscillator that generates an output signal input to the coil sensor selected by the selection unit; and an intensity of the output signal of the oscillator is adjusted. At least one adjusting means, a first path for inputting the output signal of the oscillator as it is to the coil sensor, and the output signal of the oscillator via the adjusting means. And a second path to be input to the sensor, and a switching means for switching in accordance with the arrangement location of the coil sensor is selected in the selection circuit.

  According to the present invention, an error in position detection results due to noise or the like, in particular, an error in the outer peripheral portion of the liquid crystal display device, and a position detection device that stably detects the position selected by the position pointing device, and A liquid crystal display device using can be provided.

  A liquid crystal display device according to a first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a liquid crystal display device 100 includes a liquid crystal display panel 10, a surface light source device 20 that illuminates the liquid crystal display panel 10 from the back, and a position detection device 30 that is disposed on the back side of the surface light source device 20. A bezel cover 40 that holds the periphery of the liquid crystal display panel 10 and the surface light source device 20 is provided. The bezel cover 40 is made of metal.

  The liquid crystal display panel 10 includes a pair of substrates arranged opposite to each other, that is, an array substrate 12 and a counter substrate 14, and a liquid crystal layer LQ held between the array substrate 12 and the counter substrate 14. The liquid crystal display panel 10 has a substantially rectangular display area 11 for displaying an image.

  The display area 11 is composed of a plurality of pixels PX arranged in a matrix. The array substrate 12 has a plurality of scanning lines Sc extending along the row direction (X direction) of the pixels PX and a plurality of signal lines extending along the column direction (Y direction) of the pixels PX in the display region 11. Sg, a switching element SW arranged for each pixel PX in the vicinity of the intersection of the scanning line Sc and the signal line Sg, a pixel electrode PE connected to the switching element SW, and the like. The counter substrate 14 includes a counter electrode CE and the like common to all the pixels PX in the display region 11.

  The array substrate 12 and the counter substrate 14 are disposed with the pixel electrode PE and the counter electrode CE facing each other, and a gap is formed between them. The liquid crystal layer LQ is formed of a liquid crystal composition sealed in the gap between the array substrate 12 and the counter substrate 14.

  The circuit board 18 is electrically connected to one side edge of the liquid crystal display panel 10 via the flexible board 16 and supplies a drive signal to the liquid crystal display panel 10. The circuit board 18 is disposed on the back side of the surface light source device 20 by curving the flexible substrate 16 toward the back side of the surface light source device 20.

  The surface light source device 20 has a substantially rectangular emission region 20A that emits illumination light. The surface light source device 20 is stacked on the back surface of the liquid crystal display panel 10 so that the emission region 20A and the display region 11 of the liquid crystal display panel 10 correspond to each other. In this state, the liquid crystal display panel 10 and the surface light source device 20 are accommodated in the frame 50. Further, the liquid crystal display panel 10 and the surface light source device 20 are attached with a bezel cover 40 from above and are held around.

  As illustrated in FIGS. 1 and 2, the position detection device 30 includes a sensor unit 300 including a sensor region 302 and a detection unit 310 that transmits and receives signals to and from the sensor unit 300.

  The position detection device 30 is disposed on the back side of the surface light source device 20 so that the sensor region 302 and the display region 11 of the liquid crystal display panel 10 correspond to each other.

  The sensor region 302 includes a plurality of coil sensors arranged in a plane. In this embodiment, a plurality of coil sensors Xn extending in the Y direction (n = 1, 2,... A, A: total number of coil sensors extending in the Y direction) and a plurality of extending in the X direction. Coil sensor Ym (m = 1, 2,... B, B: total number of coil sensors extending in the X direction), for example, 40 coil sensors X1 to X40 extending in the Y direction, and extending in the X direction The existing 40 coil sensors Y1 to Y40 are provided.

  Around the sensor region 302, a selection circuit 304 connected to the coil sensors Xn and Ym is provided. The selection circuit 304 is a selection unit that sequentially selects coil sensors that transmit or receive signals from the plurality of coil sensors Xn and Ym. The selection circuit 304 is connected to the detection unit 310.

  The detection unit 310 is connected to the signal generation unit 320 that outputs a signal input to the coil sensor, the signal reception unit 330 that receives signals from the coil sensors Xn and Ym, and the signal generation unit 320 and the signal reception unit 330. A transmission / reception switching unit 340 for switching transmission / reception of signals to the coil sensors Xn and Ym, and a central processing unit (hereinafter referred to as CPU) 350.

  The signal generator 320 includes an oscillator 322 that generates a signal input to the coil sensors Xn and Ym. The oscillator 322 generates an AC signal having a constant frequency, and its output terminal is connected to the current driver 324. The current driver 324 converts the output signal of the oscillator 322 into a current.

  The current signal output from the current driver 324 is input to the switching circuit 326. The output terminal of the switching circuit 326 is connected to one of the first path r1 and the second path r2. That is, the switching circuit 326 is controlled by the CPU 350 to switch the connection to the first path r1 or the second path r2. The second path r2 is provided with an amplifier 328 as adjusting means. The output signal of the switching circuit 326 is input to the transmission / reception switching unit 340 via either the first path r1 or the second path r2.

  On the other hand, the signal reception unit 330 includes a reception buffer 332 that receives an output signal of the transmission / reception switching unit 340. The output signal of the reception buffer 332 is input to the detection circuit 334. The detection circuit 334 extracts a specific signal from the signal input from the reception buffer 332 and outputs it. The output terminal of the detection circuit 334 is connected to the low pass filter 336. The low pass filter 336 removes high frequency components of the input signal. The output signal of the low pass filter 336 is input to the sample hold circuit 338.

  In the sample hold circuit 338, the output signal of the sample hold circuit 338 is input to an analog / digital conversion circuit (hereinafter referred to as A / D conversion circuit) 339. An output signal of the A / D conversion circuit 339 is input to a central processing unit (hereinafter referred to as CPU) 350.

  The CPU 350 controls operations of the selection circuit 304, the switching circuit 326, the sample hold circuit 338, the A / D conversion circuit 339, and the transmission / reception switching unit 340.

  Next, the operation of the position detection device 30 will be described with reference to FIGS.

  The oscillator 322 generates an AC signal having a specific frequency, for example, a frequency f1, and outputs the AC signal. An output signal of the oscillator 322 is input to the current driver 324. The current driver 324 converts the input AC signal into a current signal and outputs the current signal. An output signal of the current driver 324 is input to the switching circuit 326.

  The switching circuit 326 is controlled by the CPU 350 and the connection is switched to one of the first path r1 and the second path r2. When the switching circuit 326 is connected to the first path r1, the current signal output from the switching circuit 326 is input to the transmission / reception switching unit 340 as it is. When the switching circuit 326 is connected to the second path r2, the current signal output from the switching circuit 326 is input to the transmission / reception switching unit 340 via the amplifier 328.

  That is, when the switching circuit 326 is connected to the second path r2, the intensity of the current signal input to the switching circuit 326 is amplified and input to the transmission / reception switching unit 340.

  Here, the selection circuit 304 selects the coil sensors (in this embodiment, the coil sensors Y1, Y2, Y39, Y40, and the coil sensors X1, X2, X39, X40) arranged around the sensor region 302. In this case, the switching circuit 326 is connected to the second path r2, and when a coil sensor other than the above (in this embodiment, the coil sensors Y3 to Y38 and the coil sensors X3 to X38) is selected, the switching circuit 326 326 is connected to the first route r1.

  In the present embodiment, the current input to the coil sensor via the first path r1 is about 0.5 mA, and the current input to the coil sensor via the second path r2 is about 1 mA.

  As described above, the output signal output from the switching circuit 326 is input to the transmission / reception switching unit 340 as the output of the signal generation unit 320. The transmission / reception switching unit 340 is controlled by the CPU 350 and the connection is switched between the transmission side and the reception side at a fixed timing. When the connection of the transmission / reception switching unit 340 is switched to the transmission side, the current signal input from the signal generation unit 320 to the transmission / reception switching unit 340 is output toward the selection circuit 304.

  The current signal input from the transmission / reception switching unit 340 to the selection circuit 304 is input to the coil sensor selected by the selection circuit 304. As shown in FIG. 3, the selection circuit 304 is controlled by the CPU 350 so that the coil sensors X1 to X40 and the coil sensors Y1 to Y40 are fixed in the order of Y1, Y2,..., Y40, X1, X2,. Select by timing.

  For example, when the selection circuit 304 selects the coil sensor Y4, a current flows through the coil sensor Y4 and an alternating magnetic field is generated. Here, the alternating magnetic field generated by the coil sensor Y4 has the same frequency f1 as the signal output from the oscillator 322. Hereinafter, a case where the selection circuit 304 selects the coil sensor Y4 will be described.

  At this time, if the position indicating device 32 for indicating the position of any of the coil sensors Xn and Ym is near the coil sensor Y4, the resonance circuit 32A of the position indicating device 32 resonates with the magnetic field generated by the coil sensor Y4. That is, the frequency f1 of the magnetic field generated by the coil sensor Y4 is a resonance frequency with respect to the capacitance C of the capacitor included in the resonance circuit 32A and the inductance L of the coil. The resonant magnetic field generated by the resonant circuit 32A is input to the switching circuit via the coil sensor Y4.

  The resonant magnetic field input to the selection circuit 304 is input to the transmission / reception switching unit 340. When the connection of the transmission / reception switching unit 340 is switched to the reception side, the resonance magnetic field is output from the transmission / reception switching unit 340 and input to the reception buffer 332. The reception buffer 332 outputs the input signal toward the detection circuit 334. The detection circuit 334 extracts a resonance frequency component from the input signal and outputs it to the low-pass filter 336.

  The low-pass filter 336 removes the high frequency component of the input signal and outputs it to the sample hold circuit 338. The sample hold circuit 338 samples the value of the input signal at an arbitrary timing and holds the value for a predetermined period. The sample hold circuit 338 is controlled by the CPU 350 at the timing for sampling the signal value and the period for holding the value.

  The signal output from the sample hold circuit 338 is input to the A / D conversion circuit 339 and converted into a digital signal. The digital signal output from the A / D conversion circuit 339 is input to the CPU 350.

  Similar to the case where the coil sensor Y4 described above is selected, the magnitude of the output signal output from the oscillator 322 is adjusted by switching the path by the switching circuit 326, and the coil sensor selected by the selection circuit 304 is selected. Input to Xn and Ym. Then, an electric field having an intensity corresponding to the distance from the position pointing device 32 is output from the coil sensor to which the current signal is input. The electric field output from the coil sensor is input to the CPU 350 via the signal receiving unit 330. The CPU 350 obtains the coordinate value of the position selected by the position pointing device from the distribution of the electric field strength output from each of the coil sensors Xn and Ym.

  In general, when the bezel cover 40 formed of metal is around the sensor unit 300, the coil sensors X 1, X 2, Y 1, and Y 2 arranged around the sensor region 302 may be located even when the position pointing device 32 is nearby. In some cases, the strength of the electric field is weakened.

  Therefore, in the above embodiment, the intensity of the current signal input to the coil sensors X 1, X 2, Y 1, Y 2 disposed around the sensor region 302 is increased by the amplifier 328. Thereby, even if it is coil sensor X1, X2, Y1, Y2 arrange | positioned around the sensor area | region 302, the intensity | strength of an electric field does not become weak and the position of the position pointing device 32 can be detected stably.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the following description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As illustrated in FIG. 4, the position detection device 30 includes a sensor unit 300 including a sensor region 302 and a detection unit 310 that transmits and receives signals to and from the sensor unit 300. Furthermore, the detection unit 310 includes a signal generation unit 320, a signal reception unit 330, a transmission / reception switching unit 340, and a CPU 350.

  The signal generation unit 320 includes an oscillator 322, a current driver 324, and a variable resistor 328A as an adjustment unit. The oscillator 322 generates an AC signal having a constant frequency. An output signal of the oscillator 322 is input to the current driver 324. The current driver 324 converts the output signal of the oscillator 322 into a current.

  The current signal output from the current driver 324 is input to the transmission / reception switching unit 340 via a variable resistor 328A serving as an adjusting unit. The resistance value of the variable resistor 328 </ b> A is controlled by the CPU 350 and adjusts the intensity of the current signal output from the current driver 324.

  That is, when the selection circuit 304 selects the coil sensors X3 to X38 and the coil sensors Y3 to Y38, the resistance value of the variable resistor 328A is controlled to be a predetermined value. On the other hand, when the selection circuit 304 selects the coil sensors X1, X2, X39, X40 and the coil sensors Y1, Y2, Y39, Y40 arranged around the sensor region 302, the variable resistor 328A The resistance value is controlled to be smaller than a predetermined value. That is, the resistance value of the variable resistor 328A is determined by the current signals input to the coil sensors X1, X2, X39, and X40 and the coil sensors Y1, Y2, Y39, and Y40 arranged around the sensor region 302 other than the above. It is controlled so as to be larger than current signals input to the coil sensors X3 to X38 and the coil sensors Y3 to Y38.

  As described above, the signal generator 320 includes the variable resistor 328A that adjusts the intensity of the current signal input to the coil sensor, so that the same effect as that of the first embodiment can be obtained.

  Furthermore, since the signal transmission unit does not need to have a path for each magnitude of the current signal to be output, the apparatus can be reduced in size. In addition, since the resistance value of the variable resistor 328A can be controlled to a plurality of values by the CPU 350, it is possible to cope with the noise characteristics of a plurality of patterns.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  For example, in the first embodiment, the amplifier 328 is used as an adjustment unit that adjusts the intensity of the current signal transmitted to the coil sensors X1, X2, Y1, and Y2 arranged around the sensor region 302. A variable resistor may be used.

  In the first embodiment and the second embodiment, the intensity of the current input to the coil sensors X1, X2, Y1, and Y2 is increased, but the characteristics of noise applied to the coil sensors Xn and Ym are increased. Correspondingly, a strong current may be input to the coil sensor that is susceptible to noise. As a result, the position of the position indicating device 32 can be detected stably as in the above embodiment.

  Further, the position detection device 30 sequentially selects the coil sensors Xn and Ym extending in the X direction and the Y direction by one selection circuit 304, and a selection circuit for selecting one of the coil sensors Xn; A selection circuit for selecting one of the coil sensors Ym may be provided. In that case, the detection unit 310 may also be provided in each of the coil sensor Xn and the coil sensor Ym. By providing a plurality of selection circuits in this way, the selection circuit is not controlled at high speed.

  In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  For example, in the first embodiment described above, the switching circuit 326 switches between two paths, the first path r1 and the second path r2, but three or more paths may be switched. In this case, the influence of noise can be further reduced by providing adjusting means in a plurality of paths and switching the paths in accordance with the characteristics of noise applied to the coil sensors Xn and Ym.

  Further, the CPU 350 may have a learning function so that stable position detection can be performed. In that case, it is possible to cope with a change in noise characteristics due to an environment in which the liquid crystal display device is used.

1 is an exploded perspective view showing an example of a liquid crystal display device according to an embodiment of the present invention. The figure which shows the example of 1 structure of the position detection apparatus which concerns on 1st Embodiment of this invention. The figure explaining the example of 1 operation | movement of the position detection apparatus shown in FIG. The figure which shows the example of 1 structure of the position detection apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display panel, PX ... Display pixel, 20 ... Surface light source device, 30 ... Position detection apparatus, 32 ... Position indication apparatus, 32A ... Resonance circuit, 300 ... Sensor part, Xn, Ym ... Coil sensor, 302 ... Sensor area | region , 304 ... selection circuit, 310 ... detection unit, 320 ... signal generation unit, 322 ... oscillator, 326 ... switching circuit, 328 ... amplifier, 328A ... variable resistor, r1 ... first path, r2 ... second path, 330 ... signal Receiving unit, 340 ... transmission / reception switching circuit

Claims (6)

A sensor unit comprising a plurality of coil sensors arranged in a plane and a selection means for sequentially selecting the plurality of coil sensors;
An oscillator that generates an output signal input to the coil sensor selected by the selection means;
At least one adjusting means for adjusting the intensity of the output signal of the oscillator;
The selection circuit selects a first path for directly inputting the output signal of the oscillator to the coil sensor and a second path for inputting the output signal of the oscillator to the coil sensor via the adjusting means. Switching means for switching according to the arrangement location of the coil sensors.   The position detection device according to claim 1, wherein the switching unit selects the second path when the selection unit selects a coil sensor arranged around the sensor unit.   The position detecting device according to claim 1, wherein the adjusting means is an amplifier for amplifying a signal generated in the oscillator.   2. The position detection device according to claim 1, wherein the adjusting means is a variable resistor that changes the intensity of a signal generated in the oscillator. A sensor unit comprising a plurality of coil sensors arranged in a plane and a selection means for sequentially selecting the plurality of coil sensors;
An oscillator for generating an output signal input to the coil sensor selected by the selection means;
Adjusting means for adjusting the intensity of the output signal of the oscillator;
And a control means for controlling the adjusting means in accordance with a place where the coil sensor selected by the selecting means is arranged. A liquid crystal display panel in which a plurality of display pixels are arranged in a matrix;
A surface light source device disposed on the back surface of the liquid crystal display panel;
The position detection device according to claim 1 or 5 disposed on a back surface of the surface light source device;
A liquid crystal display device.

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