JPH054254U - Input device - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an input device capable of surely operating a touch panel or a touch screen at low cost. [Structure] An electrode on a CRT, a step pulse generation circuit and a detection circuit connected to one side of the electrode, and a circuit which inputs a signal from the step pulse generation circuit and a signal from the detection circuit and outputs a time difference between the two signals. An input device comprising: and a dielectric placed on the contact means and detecting the position where the dielectric is placed from the impedance change of the electrode structure at that time.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an input device for detecting a position, and more particularly to an input device for detecting a position on a screen by touching a dielectric on a display screen, that is, a touch screen.

[0002]

[Prior Art]

 The touch screen of the conventional example detects the position by infrared rays. An infrared light receiving element is required for such position detection by infrared rays, but the manufacturing process of this infrared light receiving element is difficult, and the defective rate is high when commercialized. Also, infrared rays have no directivity unlike laser beams.

[0003]

[Problems to be solved by the device]

 When using a touch screen that detects the position by such infrared rays, there are problems that it is difficult to make a profit for the infrared light receiving element or the positioning accuracy is poor. The present invention is intended to solve the above problems, and is intended to realize a touch screen type input device with improved manufacturing cost and positioning accuracy.

[0004]

[Means for Solving the Problems]

 According to the present invention, a contact means having one side grounded and having an electrode structure, a CRT provided with the contact means on the surface of a screen for displaying, and a step pulse generation circuit connected to a contact which is not the ground side of the electrode. , A detection circuit that is connected to a contact that is not on the ground side of the electrode, observes a signal change at the connection point, and detects whether or not the signal is equal to or higher than a set reference voltage, A time difference measuring circuit for inputting a signal and a signal from the detection circuit and outputting a time difference between the two signals, and a control means for inputting a signal from the time difference measuring circuit to control an arithmetic process and a step pulse generating circuit are provided. The input device is characterized in that a dielectric is placed on the contact means, a step pulse is applied to the contact means, and the reflection is measured to detect the position where the dielectric is placed. It

[0005]

[Action]

 When a finger is placed on the electrode placed on the surface of the CRT, the impedance of the electrode changes, so that the position where the finger is placed can be detected by measuring the change in impedance. It should be noted that this change in impedance is detected by inputting a step pulse from the first contact of the electrode and measuring the reflection thereof, that is, measuring the time-domain-reflectometry (hereinafter referred to as TDR).

[0006]

【Example】

 FIG. 1 is a block diagram of an input device of the present invention.

In the figure, reference numeral 1 is a control means for controlling the time difference measuring circuit 2, the step pulse generating circuit 3 and the CRT 6. The time difference measurement circuit 2 inputs the oscillation signal from the step pulse generation circuit 3 and the detection signal from the detection circuit 4, measures the time difference between the two, and outputs it to the control means 1. The step pulse generation circuit 3 generates a step pulse by the signal from the control means 1 and outputs it to the contact means 5. It also outputs a transmission signal indicating the rise of the step pulse to the time difference measuring circuit 2. The detection circuit 4 receives the reflected signal from the contact means 5 and detects the signal change. One side of the contact means 5 is grounded, and the other side is an electrode connected to the step pulse generation circuit 3 and the detection circuit 4. The CRT 6 is for display used in an ordinary waveform observing device and has a structure having the contact means 5 on the surface.

The operation in such a structure will be described. A step pulse is input to the contact means 5 from the step pulse generation circuit 3 by a signal from the control means 1. This step pulse has a sufficient time width to detect the reflected wave at the contact means 5 (equivalent to the above-mentioned reflected signal), and the output impedance of the step pulse generation circuit 3 is the end of the contact means 5. It should be commensurate with the resistance. The detection circuit 4 inputs a signal waveform (combined of a step pulse and a reflected signal) from a connection point with the contact means 5, and this signal is reflected at a dielectric on the contact means 5 there. Changes appear in the signal waveform, the signal change is detected and a detection signal is output. In the time measuring circuit 2, the time from the rise of the step pulse to the detection signal is measured, and the time width from the rise of the step pulse to the fall of the signal waveform showing the reflection from the ground portion of the contact means 5 is measured. The controller 1 calculates the ratio with the measurement result to detect the position of the dielectric.

FIG. 2 is a block diagram of an embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals. The control means 1 in FIG. 1 is a CPU, the time measuring circuit 2 is a counter or the like, the step pulse generating circuit 3 is a step recovery diode D, a sampler S or the like, and the detection circuit 4 is a comparator or the like. The contact means 5 is composed of an electrode, and the material thereof is, for example, a transparent electrode used in a liquid crystal, and is embedded in a filter or the like covering the surface of the CRT with the structure shown in FIG. This is to prevent the electrodes from interfering with the display screen of the CRT. When a dielectric such as a finger approaches the contact means 5, the impedance of the contact means 5 changes.

The operation of the configuration of this embodiment will be described with reference to FIG. 3 shows a signal waveform appearing at the connection point p between the detection circuit 4 and the contact means 5, FIG. 3 (a) shows a signal waveform observed when there is no dielectric on the contact means 5, and (b). Shows a signal waveform observed when a dielectric is present on the contact means 5. A signal waveform when the contact means 5 has no dielectric will be described. The step pulse generation circuit 3 generates a step pulse by a signal from the CPU. This step pulse is input to the electrode 5, and its reflection can be observed at the connection point p. Since the electrode 5 is grounded in this embodiment, the signal waveform shown in FIG. 3A appears at the connection point p. The time width of this signal at H level is (T). When the electrode 5 has a dielectric, reflection occurs where the dielectric is on the electrode 5. Therefore, if a capacitive dielectric such as a finger is placed, the signal waveform shown in Fig. 3 (b) becomes the connection point. Appears in p. The change shown by b in Fig. 3 (b) is proportional to the distance between the place where the capacitive dielectric is placed and the connection point. For example, the position of the dielectric can be detected. The position detection will be described. Since the comparator 4 uses the reference voltage Vh ', its output is inverted when the level becomes lower than Vh which is the level of the signal waveform at which reflection is observed. In the signal waveform counter 2 as shown in a and b of FIG. 3, the counting is started at the rising edge of the step pulse, and the counting is ended by inverting the output of the comparator 4. If there is no dielectric, (T) is counted, and if there is a dielectric, (t) is counted. If L is the length of the electrode, the distance l from the connection point p of the electrode of the dielectric can be calculated by l = L × (t / T). Therefore, this calculation is performed by the CPU, and where the dielectric is placed. It is possible to detect that

[0011]

[Effect of the device]

 As described above, according to the input device of the present invention, the operation of the touch panel or touch screen can be reliably performed at low cost by performing the TDR measurement.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a detailed configuration diagram of an embodiment of the present invention.

FIG. 3 is a diagram showing a time chart of an electrical change of a reflected signal in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Control means, 2 ... Time difference measurement circuit, 3 ... Step pulse generation circuit, 4 ... Detection circuit, 5 ... Contact means, 6 ... CRT, D ... Step recovery diode, S ... Sampler.

Claims (1)

[Claims for utility model registration] [Claim 1] A CRT having contact means, one of which is grounded and has an electrode structure, and the contact means provided on the surface of a screen for displaying.
A step pulse generation circuit connected to the contact not on the ground side of the electrode, and a step pulse generation circuit connected to the contact not on the ground side of the electrode, observing a signal change at the connection point, and the signal is equal to or higher than a set reference voltage. A detection circuit for detecting whether or not, a time difference measurement circuit which inputs a signal from the step pulse generation circuit and a signal from the detection circuit and outputs a time difference between the two signals, and a signal from the time difference measurement circuit , Providing control means for controlling the arithmetic processing and the step pulse generation circuit,
An input device, characterized in that a dielectric is placed on the contact means, a step pulse is given to the contact means, and the reflection thereof is measured to detect the position where the dielectric is placed.