JPH05274085A - Input and display device - Google Patents

Abstract

PURPOSE:To eliminate a derived component superimposed on a signal by providing an integration circuit which adds a reception signal on a processing circuit to process the signal of a position sensor substrate for plural times. CONSTITUTION:A reception circuit 7 selects the resonance electromagnetic wave of an indicator 8 which resonates with an electromagnetic wave radiated from the loop coil 51 of an oscillator 63, and judges that the maximum reception value should be taken when which loop coil 51 is selected, and also, the amount of deflection is found from the output value of a neighboring loop coil 51 at that time. The integration means of a waveform processing circuit 72 in the reception circuit 7 is to perform the delay by one cycle of a burst signal, and the reception signals for the same loop with different number of times appear at an input part and an output part on an analog delay line by supplying the burst signal to the same loop for plural times. An original signal can be doubled by adding such signal by an analog adder, and a noise component appears at random, which results mutual negation. Therefore, noise elimination synchronized with the burst signal can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input and display device having a so-called coordinate input device.

[0002]

2. Description of the Related Art Conventionally, as shown in JP-A-63-53595 and JP-A-63-70326, liquid crystal cells and position sensor means are laminated and coordinate input (key input Input and display devices have been proposed. As one of these so-called input and display devices with a coordinate input device, there is a device that uses a proximity sensor or a position sensor means of an electromagnetic transfer action method. In these methods, a position sensor substrate is provided below a liquid crystal cell. Are arranged and the coordinates are detected when the display surface is pointed by an indicator or the like.

[0003]

However, these electromagnetic transmission / reception systems and proximity sensors are vulnerable to changes and excursions of magnetic fields and electric fields. On the other hand, liquid crystal cells are dark and have low contrast unless an illuminating means is used. Have difficulty. However, since the light source and the lighting circuit used for the illuminating means tend to displace the magnetic field and the electric field or generate noise, both of them are often inconvenient for recognizing the coordinate position, which is inconvenient.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points. First, a processing circuit for processing a signal of a position sensor substrate has an integrating means for adding a received signal a plurality of times. Is provided. The present invention secondly provides a processing circuit for processing the output of the position sensor substrate with a filter circuit for the driving frequency of the illumination means.

Thirdly, the output of the position sensor substrate is added a plurality of times by the integrating means a signal that has passed through a filter circuit for the drive frequency of the illuminating means, and position calculation is performed based on the outputs of these filter circuits and integrating means. Means are provided.

[0006]

As a result, the inductive component superimposed on the signal is removed.

[0007]

1 is a sectional view a of an input and display device and a block diagram b of a processing circuit according to an embodiment of the present invention. In the figure, reference numeral 1 is a field effect type liquid crystal cell.
This is a so-called super twist nematic liquid crystal display which is twisted by 20 degrees, and polarizing plates are attached to both surfaces of the substrate so that the liquid crystal layer is sandwiched between the outer surfaces of the substrate. Reference numeral 2 denotes a liquid crystal driving element arranged around the liquid crystal cell 1. It is preferable that the driving element 2 has a short distance from the side in the longitudinal direction of the integrated circuit to the liquid crystal cell because it is uniform with respect to the magnetic field. 3 is a liquid crystal cell 1
Is a hard transparent plate disposed on the display surface side of, and is made of a plate glass or an acrylic resin plate having a sufficient thickness, and a certain space is secured between the liquid crystal cell 1 and the hard transparent plate 3, which is undesired. Prevent the display and coloring from appearing.

Numeral 4 is a lighting means which is arranged on the back surface of the liquid crystal cell 1 and is driven by alternating current. And a light-reflecting sheet such as white glossy paper or paper coated with a pigment is attached, and a light-diffusing sheet is attached to the surface, and a light guide plate 4
1. A light source 42 including a cold cathode tube arranged on one side surface
And a lighting circuit section 43 for lighting the light source 42 with an AC signal around 70 kHz.

Reference numeral 5 denotes a position sensor substrate disposed below the light guide plate 4 and fixed to the bottom surface of the frame with screws or the like, which is a substrate used for position sensor means of an electromagnetic transfer action system, and is made of a resin such as glass epoxy. As a material, a plurality of loop coils 51, which are displaced from each other, are arranged in a portion of the surface corresponding to the effective display area of the liquid crystal cell 1. Reference numeral 6 denotes a signal processing unit that applies an AC signal to the loop coil 51 of the position sensor substrate 5 and detects a received signal, and a loop selector 61 that sequentially selects a specific loop coil 51, and an oscillator 63 for the selected loop coil 51. An AC signal of a predetermined frequency is applied or its loop coil 51 is connected to the receiving circuit 7
Switching device 62 for selecting whether to connect to and to receive a signal
And a control unit 65 including a microprocessor for controlling these loop selectors and the like. Of these, the oscillator 63 oscillates a rectangular wave of 530 kHz, for example. Further, the receiving circuit 7 has a filter 71 for selecting a signal of the frequency of the oscillator 63, a waveform processing circuit 72 for waveform shaping and standardizing the signal of the filter 71, and an operation based on the output of the waveform processing circuit 72 to calculate the position coordinate of the indicator. Calculation unit 73 for obtaining
The waveform processing circuit 72 has a built-in integrating means including an analog delay line for adding received signals a plurality of times and an adder made of an operational amplifier for each burst time delay of the analog delay line. Accordingly, by having an A / D converter, the subsequent processing is processed with digital values.

The receiving circuit 7 selects the resonance electromagnetic wave of the indicator 8 that resonates with the electromagnetic wave radiated from the loop coil 51 of the oscillator 63, and determines which loop coil 51 has the maximum reception value. The amount of deviation is determined from the output value of the adjacent loop coil 51 at that time,
It is possible to find the position where the indicator 8 is located further in the elongated loop coil 51 than in the longitudinal direction. By arranging the loop coil 51 in two directions orthogonal to each other, the absolute coordinates can be calculated.
Therefore, the indicator 8 is provided with an LC resonator corresponding to this radiation frequency. The position sensor means is composed of the substrate 5, the signal processing unit 6, and the indicator 8.

In such a structure, when the position sensor means is of the electromagnetic transfer action type as described above, a plurality of loop coils 5 arranged on the surface of the position sensor substrate 5 are provided.
An alternating electric field having a predetermined frequency is applied in a burst manner in order from the loop having 1 at one end, and the same loop is placed in the receiving state this time. Then, if there is no resonator (indicator 8) for a predetermined frequency in the vicinity, the loop coil 51 receives nothing, but when the indicator 8 is located, the resonator resonates due to the application of the electric field to maintain the resonance. Same loop coil 5
It will be detected by 1. Since the intensity of this reception changes according to the distance between the resonator and the loop coil, the position of the resonator can be determined by sequentially changing the position of the loop coil. If there is a predetermined noise source in the vicinity of these, a specific superimposed signal is induced in the signal received by the loop coil, and therefore sensitivity determination cannot be performed. However, the area in which the sensitivity cannot be determined is not all loop coil positions, and the superimposed signal is not limited to, for example, the driving AC of the illumination means. When the sensitivity cannot be determined, the superimposed signal can be filtered by the filter 71 described above. However, since the waveform is saturated, the present invention treats it as so-called noise and removes it.
In the above configuration, the integrating means of the waveform processing circuit 72 of the receiving circuit 7 delays one cycle of the burst signal. When the burst signal is applied to the same loop a plurality of times, the analog delay line has an input section and an output section. Received signals for the same loop appear different times in the section. When these are added by the analog adder, the original signal component becomes twice as large, and the noise components are random in time, so they cancel each other out. Therefore, noise removal synchronized with the burst signal is performed. If the amplification factor of the adder is set to 1 for the input signal line, its output can be treated as a signal component extracted.

Such an integrating means can digitally operate using an A / D converter, a memory and an adder or an ALU. That is, the input signal is sampled at a predetermined timing from the reception start time synchronized with the burst signal, converted into an 8-bit digital value, and stored in the memory.
After the end of one burst period, the sampled digital value corresponding to the A / D conversion of the next burst period and the digital value stored in the memory are added by an adder, and the envelope value of the sample time unit is taken to be integrated. You can get a signal. Noise removal may be performed in this manner.

Further, in the above-described embodiment, the noise directly propagated from the power source of the illumination means cannot be completely removed because it has a fixed cycle. For such noise, a notch-type filter circuit for the drive frequency of the illumination unit 4 may be provided in the processing circuit that processes the output of the position sensor substrate 5. Since the above-mentioned filter 71 has to be a bandpass filter due to its character,
Those that cannot be completely filtered can be efficiently removed with a notch filter.

Such a notch filter may be provided in the preceding stage of the filter 71 or in the preceding stage of the waveform processing circuit 72, or in the latter stage thereof, but it is preferable to arrange it between the filter 71 and the waveform processing circuit 72. This means that those that are difficult to remove when superposed on a predetermined received signal are processed lastly, so that the filter 71 removes general noise, removes specific frequency noise due to the illumination means, and finally removes unspecified noise. This is because it is possible to efficiently extract the signal component.

[0015]

As described above, it is less likely that the position coordinates will be difficult to determine due to the auxiliary device such as the illumination means because it is overlapped with the display, and the display quality can be kept good.

[Brief description of drawings]

FIG. 1 is a sectional view a of an input and display device according to an embodiment of the present invention.
2 is a block diagram b of the processing circuit.

[Explanation of symbols]

 1 liquid crystal cell 4 illumination means 5 position sensor substrate 6 processing circuit unit 7 receiving unit

Claims (3)

[Claims] 1. An input and display device comprising a liquid crystal cell, a position sensor substrate used for electromagnetic sensor position sensor means arranged below the liquid crystal cell, and a processing circuit for processing a signal of the position sensor substrate. In the input and display device, the processing circuit is provided with an integrating means for adding the received signals a plurality of times. 2. A process for processing an output of a position sensor substrate, comprising a liquid crystal cell, illumination means arranged on the back surface of the liquid crystal cell and driven by an alternating current, and a substrate used for position sensor means laminated on the liquid crystal cell. An input and display device characterized in that the circuit is provided with a filter circuit for the drive frequency of the illumination means. 3. An input and display device comprising a liquid crystal cell, a position sensor substrate used for an electromagnetic transfer type position sensor means arranged below the liquid crystal cell, and a processing circuit for processing a signal of the position sensor substrate. In the processing circuit, a filter circuit for the drive frequency of the illuminating means, an integrating means for adding the output signals of the filter circuit a plurality of times, and an operating means for performing a position operation based on the output of the integrating means are provided. An input and display device characterized by: