JP2000172420A - Pressure-sensitive resistance film digitizer circuit constant estimating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for finding an index indicating dynamic characteristics of a pressure-sensitive resistance film digitizer in two-layered structure. SOLUTION: The pressure-sensitive resistance film digitizer in two-layered structure is regarded as an equivalent circuit of a main resistor 204a, a 2nd resistor 202, and inter-film capacitors 211 and 212 between the main and 2nd resistor; and step response is observed by applying a ground-level potential (0 V) to one terminal 206 and a step input to the other terminal 205 through the resistance and compared with the logically calculated value to estimate the circuit constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of evaluating a resistive digitizer, and more particularly to a method of estimating a circuit constant of a resistive digitizer.

[0002]

2. Description of the Related Art As shown in FIG. 1, a resistive film pressure-sensitive digitizer 100 includes a base 101 made of glass or a film, and a conductive film 10 provided on the base 101.
2 and an insulating film 103 provided over the conductive film 102
And a main resistance film 104 provided on an upper layer of the insulating film 103 and related to coordinate detection, and electrodes 105 and 106 disposed at both ends of the main resistance film 104.
This configuration is excellent in electrical characteristics and optical characteristics (light transmission).

In general, indexes indicating the characteristics of a resistive film digitizer include a linearity of a resistive film, a resistance value between electrodes, an insulation resistance value between resistive films, a capacitance value between resistive films, and the like. The resistance film pressure-sensitive digitizers currently on the market use a so-called static characteristic measurement method that detects the place where the measured value is sufficiently stable by applying a pen load for a long time, and confirms the operation.
The measurement results are published. Therefore, when designing a system using a digitizer, the design is performed with reference to the published values measured by the method for measuring static characteristics.

When a system design that does not require high-speed operation, such as the digitizer sampling speed, is designed, a digitizer whose operation has been confirmed only by the above-described static characteristic measurement method can be sufficiently used. When it is necessary to increase the speed or operation speed, in the digitizer 100 having the two-layer structure, the capacitor component between the main resistance film 104 as the first resistance film and the conductive film 102 as the second resistance film is reduced. In some cases, when the digitizer is operated at high speed, the response of the output to the input is slow and an accurate coordinate value cannot be obtained.

Therefore, when designing a system using a digitizer, it is necessary to know whether or not the digitizer is a digitizer that can cope with high-speed operation. Therefore, in the case where the pen load is applied only for a moment, for example, an index representing a so-called dynamic characteristic for detecting a response speed at the time of high-speed operation is required.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for obtaining an index representing dynamic characteristics of a two-layer resistive pressure-sensitive digitizer.

[0007]

According to the present invention, claim 1 is provided.
In the method for estimating the circuit constant of a two-layer resistive film pressure-sensitive digitizer having a second resistive film with an insulating film below a main resistive film, an equivalent circuit is applied to the two-layer resistive film pressure-sensitive digitizer. The circuit constant of the two-layer resistive film pressure-sensitive digitizer is estimated based on the equivalent circuit.

According to a second aspect of the present invention, in a method of estimating a circuit constant of a two-layer resistive film pressure-sensitive digitizer having a second resistive film via an insulating film below a main resistive film, the resistive film is disposed at both ends of the resistive film. The two-terminal circuit element is regarded as a two-terminal circuit element, and a resistance element corresponding to the second resistance film and a capacitor element corresponding to an inter-film capacitance between the main resistance film and the second resistance film are connected in series. , An equivalent circuit of the two-layer resistive film pressure-sensitive digitizer in which a resistance element corresponding to the main resistive film is connected in parallel, and a circuit of the two-layer resistive film pressure-sensitive digitizer based on the equivalent circuit. It is characterized by estimating a constant.

According to a third aspect of the present invention, in the second aspect, a step input is performed to the electrode, a value obtained by measuring a step response to be output is compared with a calculated step response value, and the film of the equivalent circuit is compared. The method is characterized in that an inter-capacitance value and a resistance value of the second resistance film are estimated.

According to a fourth aspect of the present invention, in the second aspect, the Wheatstone bridge is formed by opposing the two-layer resistive film pressure-sensitive digitizer to be measured and the equivalent circuit as a reference, and the circuit of the equivalent circuit is formed. By adjusting the constant, the equilibrium point is detected, and the inter-film capacitance value of the equivalent circuit and the resistance value of the second resistance film are estimated.

[0011]

FIG. 2 shows an equivalent circuit of the two-layer resistive pressure-sensitive digitizer shown in FIG. 1 between the electrodes 105 and 106 as a two-terminal circuit element.

In FIG. 2, reference numeral 204 denotes a main resistance R1 corresponding to the main resistance film 104 as the first resistance film in FIG. 1, and reference numeral 202 denotes a conductive film as the second resistance film in FIG. 102
And a second resistor R2 corresponding to
The electrodes 105, 10 arranged at both ends of the main resistance film 104 in FIG.
Equivalent to 6. When the resistance is the main resistance film 104 (the main resistance R1 (2
04)) may be treated as pure resistance, but in the case of a two-layer structure, the conductive film 10
2 (second resistor R2 (202)), it is assumed that there is a path through which an alternating current flows. Therefore, the main resistance film 104 (main resistor R1 (204)) and the conductive film 102 (second resistor R2 (2)
02)) and capacitors C1 (211) and C2
(212) occurs. When a resistive digitizer with a two-layer structure is strictly expressed, it is necessary to arrange a countless number of small-capacity capacitors and countless resistive films as a distributed constant circuit. When a normal electrode operation is performed as a digitizer, it can be accurately represented by an equivalent circuit composed of simple lumped circuit constants in FIG.

When coordinate detection is performed using such a digitizer, a potential difference is applied to the electrodes 205 and 206, and a state in which a potential difference is applied between the electrodes 205 and 206 and a state in which no voltage is applied are alternated. Repeat.

Next, a method for estimating the lumped circuit constant of a two-layer resistive film pressure-sensitive digitizer will be described.

First, the first method is a method of observing the step response of a resistive digitizer having a two-layer structure and estimating a circuit constant by comparing the step response with a logically calculated value.

As shown in FIG. 3, a resistor r (303) is connected in series to one electrode 105 of the resistive digitizer 100 having a two-layer structure, and a step input is applied from an input terminal 301 as shown in FIG. The other electrode 106 applies a ground level potential (0 V). When a step response is observed, the output from the terminal 302 is observed as a step response. The resistance r (303) is usually appropriate to be about 1 KΩ.

On the other hand, when the step response in the circuit shown in FIG. 2 is calculated,

[0018]

(Equation 1) Becomes

Therefore, comparing the step response observed in FIG. 3 with the result of the step response obtained by the calculation of the above equation (1), the second resistor R2 in FIG.
(202) and the approximate value of the capacitor C (211 and 212) can be estimated.

The second method is a method of estimating circuit constants by forming a Wheatstone bridge by opposing an equivalent circuit to a two-layer resistive film pressure-sensitive digitizer.

FIG. 4 shows an example of a Wheatstone bridge configuration.

One electrode 106 of the resistive digitizer 100 having a two-layer structure as a measurement sample is connected to a terminal 409, and the other electrode 105 is connected to a terminal A of a resistor 408. Reference numeral 405 denotes an equivalent circuit of the resistive film pressure-sensitive digitizer 100, which includes a main resistance 401, a second resistance film 402, and an inter-film capacitance (capacitor C4) 403 between the main resistance 401 and the second resistance film (R4) 402. Is connected to the terminal 409, and the other end is connected to the terminal B of the resistor 408.

[0023]

(Equation 2) The inter-film capacitances are regarded as the same for simplicity and are combined into one. Reference numerals 406 to 408 denote a group of resistors for constituting a Wheatstone bridge.
It is formed by the degree of resistance. The resistors 406 and 407 are connected to the terminal 410.

The terminal 409 has a ground level potential (0
V), and an AC waveform or a step-like waveform (continuous rectangular wave) is applied to the terminal 410. In this state, the values of the capacitor C4 (403) and the second resistance film R4 (402) are adjusted, and a value at which the potential difference between both ends (between A and B) of the resistor 408 becomes 0 is detected. The approximate value of the second resistor R2 (202) and the capacitors C (211 and 212) of the resistive film pressure-sensitive digitizer 100 can be estimated.

[0025]

According to the present invention, the dynamic characteristics of a two-layer resistive pressure-sensitive digitizer can be detected.

Further, assuming a state of use as a resistive film pressure-sensitive digitizer, it can be expressed by a simple lumped parameter equivalent, which is effective for application to circuit simulation and the like.

Also, the dynamic characteristics of a two-layer resistive film pressure-sensitive digitizer can be expressed by two parameters.
The quality control at the time of manufacturing a two-layer resistive pressure-sensitive digitizer is simplified.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a structure of a two-layer resistive film pressure-sensitive digitizer.

FIG. 2 is a schematic diagram showing an embodiment of a configuration of an equivalent circuit of a two-layer resistive film pressure-sensitive digitizer.

FIG. 3 is a schematic diagram showing an embodiment of a circuit of a first constant estimation method according to the present invention.

FIG. 4 is a schematic diagram showing an embodiment of a circuit of a second constant estimation method according to the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 resistive film digitizer of two-layer structure 101 base 102 conductive film 103 insulating film 104 main resistive film 105, 106 electrode 202 second resistor R2 204 main resistor R1 205, 206 electrode 211 inter-film capacitor C1 212 inter-film capacitor C2 303 Resistance r 405 Equivalent circuit of resistive film pressure-sensitive digitizer with two-layer structure 401 Main resistance of equivalent circuit 402 Second resistance R4 of equivalent circuit 403 Inter-film capacitance capacitor C4 of equivalent circuit

Continued on the front page (72) Inventor Shinsuke Morai 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. (72) Inventor Takashi Baba 2-5-5-1 Keihanhondori, Moriguchi-shi, Osaka F-term (reference) in Sanyo Electric Co., Ltd. 5B068 AA04 BB06 CC12

Claims (4)

[Claims] 1. A method of estimating a circuit constant of a two-layer resistive film pressure-sensitive digitizer having a second resistive film below an main resistive film via an insulating film, the method being equivalent to the two-layer resistive film pressure-sensitive digitizer. A method for estimating a circuit constant of a resistive digitizer of a resistive film type, characterized by applying a circuit and estimating a circuit constant of a two-layer resistive digitizer based on the equivalent circuit. 2. A method for estimating a circuit constant of a two-layer resistive film pressure-sensitive digitizer having a second resistive film via an insulating film below a main resistive film. Considering the space between the electrodes as a two-terminal circuit element, a resistance element corresponding to the second resistance film and a capacitor element corresponding to an inter-film capacitance between the main resistance film and the second resistance film are connected in series. An equivalent circuit of the two-layer resistive film pressure-sensitive digitizer in which resistance elements corresponding to the main resistive film are connected in parallel, and a circuit constant of the two-layer resistive film pressure-sensitive digitizer is estimated based on the equivalent circuit. And a method for estimating a resistive film pressure-sensitive digitizer circuit constant. 3. The inter-film capacitance value of the equivalent circuit according to claim 2, wherein a step input is performed to the electrode, and a value obtained by measuring a step response to be output is compared with a calculated step response value. And estimating a resistance value of the second resistive film. 4. The Wheatstone bridge according to claim 2, wherein the two-layer resistive film pressure-sensitive digitizer to be measured and the reference equivalent circuit are opposed to each other to adjust a circuit constant of the equivalent circuit. A resistive film digitizer circuit constant estimating method, wherein an equilibrium point is detected, and an inter-film capacitance value of the equivalent circuit and a resistance value of the second resistive film are estimated.