JPH0318995Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a coordinate input device configured to read a specified position on an input plane with high precision. [Prior Art] As an example of a coordinate input device that reads a specified position on a plane with high precision,
There is an application filed as 117761. This coordinate input device simultaneously sends scanning signals of the same phase to at least two of a plurality of conductors buried in parallel on a tablet, and coordinates the signals generated by the scanning signals sent to the conductors. The polarity of the detected signal is detected by an indicator, and it is determined that the polarity of the detected signal has been reversed.The signal level before and after the polarity is reversed is detected, and the position and the position where the polarity reversal is determined are detected. It is intended to calculate and detect the position pointed by the coordinate pointing device based on the signal level. FIG. 13 shows the principle configuration diagram of the above conventional example,
A more specific explanation will be given based on this drawing. In the figure, 1 is a switching circuit, 2 is a conductor buried parallel to the input plane, 3 is a pickup that detects the magnetic field generated by high frequency current flowing through the conductor in the form of an electric signal, 4 is an amplifier circuit, 5 is a polarity determination circuit that determines whether the polarity of the signal detected and amplified by the pickup 3 has been reversed; 6-1, 6;
-2 is a sample/hold circuit, 7 is an A/D converter, 8 is an oscillator that supplies high frequency current to conductor 2,
9 is a driver, 10 is a detection circuit, 11 is an adder,
12 represents a control device. In FIG. 13, the conventional coordinate input device first roughly detects whether the position of the pickup 3 is near any of the conductors 2. Second, the position between the conductor 2 and, for example, an adjacent conductor is detected with high precision. The details will be explained below. The first rough detection will be explained. Desired data is sent from the control device 12 to the switching circuit 1. Based on the data received, the switching circuit 1 operates the oscillator 8 and the driver 9.
The high-frequency current generated by the conductor 2 is sequentially switched so that the same current scans two adjacent conductors such as A and B, B and C, C and D, D and E, etc. of conductor 2. . The magnetic field generated by these two conductors 2 is detected in the form of an electrical signal by a pickup 3 and amplified by an amplifier circuit 4.
The amplified signal is supplied to a polarity determining circuit 5, and it is determined whether or not the polarity has been reversed corresponding to which scanning position. If it is determined that the polarity has been reversed, this is notified to the control device 12. This means that the rough position of the pickup 3 has been detected. Second, highly accurate detection will be explained. Upon receiving the notification that the polarity has been reversed, the control device 12 supplies the hold pulse to the sample/hold circuit 6-1, and at this time, the hold pulse is amplified and detected via the amplifier circuit 4 and the detection circuit 10 and is input. Hold and store signal _V2 . Next, the control device 12
A notification is issued to the switching circuit 1 to return to the state in which high frequency current was being supplied to the conductor 2 one step before. Then, a hold pulse is supplied to the sample/hold circuit 6-2, and at this time, the input signal _V1 amplified and detected via the amplifier circuit 4 and the detection circuit 10 is held and stored. The signal V ₁ and signal V ₂ stored in this manner are supplied to an adder 11 to calculate a sum signal (V ₁ +V ₂ ).
Then, this sum signal (V ₁ +V ₂ ) is supplied to the reference voltage input terminal V _REF of the A/D converter 7, and one of the signals V ₁ and V ₂ , for example, is supplied to the input terminal V _IN.
Supply V ₁ . As a result, the value of the following formula is calculated. Xi=V ₁ /V ₁ +V ₂ ...(1) In this way, the denominator value and numerator value of equation (1) are applied to the reference voltage input terminal V _REF and input terminal V _IN of the A/D converter 7, respectively. By inputting it, the value of equation (1) can be calculated without using an expensive division circuit. Also, the denominator sum signal (V ₁ + V ₂ )
Since the signal V ₁ is normalized by the value of , it is possible to always stably calculate the input coordinate value X _i even if the detected voltage fluctuates. The calculated input coordinate value X _i is notified to the control device 12. Similarly, the input coordinate value Y _i is calculated and notified to the control device 12. Then, based on the input coordinate values (X _i , Y _i ), the position coordinates (X, Y) where the pick-up exists on the input plane are calculated and output. Specifically, this coordinate input device is constructed as described above, and with this construction, the position of the pickup 3 can be detected with high precision within 0.3 mm above. [Problems to be solved by the invention] The above invention aims to improve the linearity of the change characteristics of the detected magnetic field and calculate using this linearity. In order to perform detection, the influence of the common conducting wire 2s cannot be ignored. In other words, conventional magnetic field distribution calculations have been performed on conductors that are considered to be infinitely long, so when detecting segments that detect rough positions, for example, two conductors (loops) are selected at positions where the polarity is reversed. Although the later arithmetic processing is carried out by specifying the midpoint of the common conductor 2 as shown in Fig. 14,
It was found that the magnetic field generated from s is involved, and the polarity reversal position shifts away from the common conducting wire 2s. Furthermore, even if the conductor 2 that is farthest from the common conductor 2s is selected, the influence becomes greater as the conductor approaches the common conductor 2s in the direction perpendicular to the conductor 2. Therefore, a compensation loop 21 through which a current having an opposite phase to the current flowing through the common conducting wire 2s flows is arranged near the common conducting wire 2s so as to surround the entire main loop 2m, thereby eliminating the influence of the common conducting wire 2s. I have a way of thinking. When loop 2 is selected as shown in Figure 2, assuming that the value of the current flowing through the compensation loop 21 is equal to the current flowing through the common conductor 2s (indicated by 〓〓 in the figure), the opposite is true. The magnetic fields generated by the directional currents cancel each other out, and no magnetic field is emitted to the outside. As a result, the state shown in FIG. 2 is considered to equivalently become the state shown in FIG. 3, and as a result, the polarity inversion position is shifted to the right in the figure. However, loop 2 has a common conductor 2 in the direction perpendicular to loop 2.
The influence of the magnetic field caused by s still remains, and in order to move the polarity reversal position to the midpoint of the predetermined loop 2, it is necessary to appropriately change the current flowing through the compensation loop 21 according to the coordinate position of the pickup 3. There is. In this way, in order to flow an appropriate current into the compensation loop 21 according to the coordinate position of the pickup 3,
The current driver circuit of the compensation loop 21 needs a function that can define the current value as a digital value. That is, it is necessary to vary the amplitude of the tributary current with high precision using a digital value. This requires a high-precision multiplier, D/A converter, variable gain, amplifier, analog switch, etc., making the device itself expensive. Therefore, the purpose of this idea is to
Another object of the present invention is to provide a highly accurate coordinate input device at a low cost. [Means for solving the problem] In order to solve the above problem, this invention sequentially sends scanning signals to a main loop consisting of a plurality of conductors buried parallel to each other in the input plane,
In a coordinate input device that detects a coordinate position based on a signal detected by a coordinate indicating tool that can arbitrarily point on the input plane, a wire is provided near the common conductor of the main loop, so as to surround the main loop. a compensation loop consisting of separate conductors provided in the main loop; switching means for sequentially sending scanning signals to predetermined loops of the main loop; and signals generated by the scanning signals sent to each loop using the switching means; a coordinate indicating device for detecting the polarity of the signal detected by the coordinate indicating device, a polarity determining means for determining whether the polarity of the signal detected by the coordinate indicating device is reversed, and a predetermined current flowing through each loop under the condition that the current flowing through the compensation loop is constant. Focusing on the scanning position where polarity reversal has been determined by the storage means that stores in advance a compensation value corresponding to the rough coordinate position on the input plane of the coordinate pointing tool when sending out, and the polarity determining means, detecting the rough coordinate position of the coordinate pointing tool, and calling a compensation value according to the position from the storage means;
The magnetic field strength from the loops before and after the polarity detected by the coordinate indicating device is reversed, and the magnetic field strength when the current is stopped being sent to the main loop and the constant current is sent only to the compensation loop. , and calculation means for calculating the position pointed by the coordinate pointing tool from the called compensation value. [Operation] The above means relieves the magnetic field generated by the common conducting wire (source wire) that supplies current to the main loop to some extent by flowing a constant current in the opposite direction to the compensation loop, and at the same time This method attempts to detect coordinates with less error by introducing correction values and performing arithmetic processing, and the principle thereof will be explained below. If we consider the magnetic field near the area where interpolation is performed, it will be as shown in Figure 4 a, b, and c. Figure 4a
For example, the magnetic field due to the nth loop 2 is
4b shows the magnetic field due to the (n+1)th loop 2, and FIG. 4c shows the magnetic field due to the compensation loop 21. After detecting a rough area (segment), interpolation is performed in the area where the graph in FIG. 4a is negative and the graph in FIG. 4b is positive. Now, the magnetic field strength Hz from the nth loop 2 is
Hz ₁ , magnetic field strength from the n+1st loop 2
Hz is Hz ₂ , magnetic field strength from compensation loop 21 Hz is Hz
c, the combined magnetic field strength of each loop 2 and the compensation loop 21 is Hz ₁ +Hzc (1) Hz ₂ +Hzc (2). Therefore, when detecting it as a voltage, it is detected with the following values, with the proportionality constant being α: V ₁ = α | Hz ₁ + Hzc | ...(3) V ₂ = α | Hz ₂ + Hzc | ...(4) , considering the sign of Hz, it can be expressed as V ₁ =α|Hz ₁ |−α|Hzc| V ₂ =α|Hz ₂ |+α|Hzc|. Considering the correction by calculation here, Hz ₁ , Hz ₂ ,
When detecting Hzc individually, the detection voltage at Hz ₁ is set as V ₁ ', the detection voltage at Hz ₂ is set as V ₂ ', and the compensation current value (ratio) ISC is set equal to the current value flowing through each loop, that is, ISC = 1, the detected voltage due to the magnetic field from the compensation loop 21 alone is
Let Vc be the compensation factor for the nth loop.
ISC, the compensation factor for the n+1th loop is
ISC ₂ , then the detected voltage after correction is V ₁ = V ₁ ′−ISC ₁・Vc……(7) V ₂ =V ₂ ′+ISC ₂・Vc……(8), and the interpolated value X is , X=V ₁ /V ₁ +V ₂ =V ₁ ′−ISC ₁・Vc/V ₁ ′+V ₂ ′+(ISC ₂ −ISC ₁ )・Vc…
…(9) becomes. Therefore, if equation (9) is used, the compensation loop 21
When V ₁ ′ and V ₂ ′ are detected with no current flowing through them, and current is flowing only through the compensation loop 21 (ISC=1)
By detecting Vc at , the interpolated value X can be found. In reality, the compensation factors ISC ₁ and ISC ₂ must be stored in advance in a storage means such as a ROM table, and after voltage detection, the predetermined compensation factors ISC ₁ and ISC ₂ must be set to be called and calculated, respectively. No. In this method, there is a large error in the Hz polarity reversal position, so there is a risk that the conditions for the interpolation region, that is, the condition that the graph in Figure 4 a is negative and the graph in Figure 4 b is positive, may not hold true. . Therefore, it is necessary to perform interpolation using the detected voltages obtained when the compensation loop 21 and each loop 2 are driven simultaneously, and in a state where the above conditions are satisfied. For this reason, if the current flowing through the compensation loop 21 is fixed to be the same as the current flowing through each loop (ISC =
In 1), the detection voltage when the n-th loop 2 and the compensation loop 21 are driven simultaneously is V ₁ ″, and the detection voltage when the n+1-th loop 2 and the compensation loop 21 are simultaneously driven is V ₂ '', the detected voltage when only the compensation loop 21 is driven is Vc. Here, using the voltages V ₁ ′ and V 2 ′ when only the nth and n+1th loops 2 are driven, respectively, V _{1 ″} =V ₁ ′−Vc ……(10) V ₂ ′=V ₂ ′−Vc ……(11) From this, V ₁ ′=V ₁ ″+Vc ……(12) V ₂ ′=V ₂ ″−Vc ……(13) ₁₂ ) _, ( ₁₃ ) into _equation ( ₉ ), we get
_C1 )・Vc...(14) Then, the interpolated value X can be found. By doing this for the Y coordinate as well,
The interpolated value Y of the Y coordinate can also be obtained in the same manner. With the above method, a current with a constant amplitude is passed through the compensation loop 21 during detection of a rough region (segment) and during interpolation within a segment as a rough region. Errors do not occur, and highly accurate detection is possible. [Example] Hereinafter, an example of this invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a coordinate input device according to an embodiment of this invention. In the figure, 21 is a compensation loop, 22 is a driver, and 23 is a ROM table, and the same components as in the conventional example are given the same reference numerals. A compensation loop 21 made of a conductor separate from the conductor 2 is provided on the outer periphery of the main loop 2m made of conductors 2 buried parallel to each other in the input plane, surrounding the main loop 2m. , one end thereof is connected to a driver 22 which receives a predetermined signal from an oscillator 8 for driving the main loop 2m and sends out a driving current. And the oscillator 8
This makes it possible to send a compensation current having the same strength as the main loop 2m to the compensation loop 21. ROM table 2 as a storage device from which the control device 12 can recall stored compensation factors;
3 stores the compensation factor ISC for each segment corresponding to the rough coordinate position as described above. This compensation factor can be achieved, for example, by embedding conductors 2 at intervals of 10 mm in the X and Y directions in a coordinate input plane on which 2 m of 200 mm x 200 mm main loops are formed, as shown in Fig. 5. An example of what is formed is as follows.

[Effect of idea]

As described above, a compensation loop is provided along the source line of the main loop, the segment where the pick-up is located is detected, the rough position is specified, and the compensation factor corresponding to that segment is stored.
The corresponding compensation factor is called from the ROM table, and the voltage within the segment is determined from the voltage detected by pick-up when the loop forming this segment is energized and the detected voltage when only the compensation loop is energized without energizing the loop. According to this invention, the position of the pick-up is determined by calculating the interpolated values of the coordinates of the segment and combining them with the coordinate values of the segment. Since there is no need to use a /D converter or the like, a highly accurate coordinate input device can be provided at low cost.

[Brief explanation of the drawing]

1 to 11 are for explaining an embodiment of this invention. FIG. 1 is a diagram showing the basic configuration of the coordinate input device according to the embodiment, and FIGS. 2 and 3 are diagrams of the compensation loop. Explanatory diagram showing the function, Fig. 4a,
b and c are diagrams each showing the state of the detected voltage, Fig. 5 is an explanatory diagram showing the loop of the coordinate input plane, and Fig. 6 is a diagram showing the state of the detected voltage.
Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11
12 are diagrams showing measurement errors, FIG. 13 is a diagram showing the basic configuration of a conventional coordinate input device, and FIG. 14 is an explanatory diagram showing an aspect of the main loop. 1...Switching circuit, 2...Conductor, 2...
...Loop, 2m...Main loop, 2s...Common conductor, 3...Pickup (coordinate indicator), 5...
...Polarity discrimination circuit, 7...A/D converter, 12...
Control device, 21... Compensation loop, 23... ROM
Table (memory means).

Claims (1)

[Claims for Utility Model Registration] Scanning signals are sequentially sent to a main loop consisting of a plurality of conductors buried parallel to each other in an input plane, and detected by a coordinate indicating tool that can arbitrarily point on the input plane. In a coordinate input device that detects a coordinate position based on a signal transmitted from the main loop, the scanning signal is sequentially sent to a compensation loop formed of a separate conductor provided near a common conductor of the main loop, and a predetermined loop of the main loop. switching means; a coordinate indicating device for detecting a signal generated by the scanning signal sent to each loop using the switching means; and determining whether the polarity of the signal detected by the coordinate indicating device has been reversed. A memory that stores in advance a compensation value corresponding to the approximate coordinate position on the input plane of the coordinate indicator when a predetermined current is sent to each loop while the current flowing through the compensation loop is kept constant. detecting the rough coordinate position of the coordinate pointing device by focusing on the scanning position where polarity reversal has been determined by the polarity determining means, and retrieving a compensation value corresponding to the position from the storage means; The magnetic field strength from the loops before and after the polarity detected by the coordinate indicating device is reversed, and the magnetic field strength when the current is stopped being sent to the main loop and the constant current is sent only to the compensation loop. , a calculation means for calculating the position pointed by the coordinate pointing tool from the called-up compensation value.