JPH0424721A - Scanning system for coordinate reader - Google Patents

Abstract

PURPOSE:To detect coordinates at high speed by calculating a position, where a second- order peak appears, from a coordinate value detected by a coordinate detection part and preventing any sense lines from being scanned except for the sense line required for calculating the coordinates and inclination at an irreducible minimum. CONSTITUTION:A control part 5 selects a sense line 3 in a rectangular area with a sense line position, where a coordinate indicator 1 exists, as a center and executes a scan processing to read an inductive voltage, and peak detection processing to calculate the sense line position of peak detection detecting the peak in the rectangular area. On the other hand, a second-order peak detection position decision processing is executed for calculating the position to generate the second-order peak according to the calculated peak detection sense line position, and a second-order peak detection processing is executed to read the second-order peak by applying the sense line position calculated by the second-order peak detection position decision processing to a scanning part 4. Thus, only the area required for coordinate calculation and second-order peak detection is scanned at an irreducible minimum, and scanning for coordinate detection can be executed at high speed while omitting the scan of any excess sense line 3.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a coordinate reading device.

[Conventional technology]

In a coordinate reading device that magnetically couples a coordinate indicator and a tablet, it is known that an error occurs in coordinate detection due to the angle formed between a coil built in the coordinate indicator and the tablet surface.

Coordinate detection errors due to inclination will be briefly explained with reference to FIGS. 3 and 4. FIG. 3 shows the coil position and induced voltage when the coordinate indicator is perpendicular to the table left surface. The indicated position 8 indicated by the coordinate indicator is located at the center of the coil 7. Since the coil is located at the center of the second grain of the sense line 3, the voltages induced in the first grain and the third grain of the sense line 3 are equal. FIG. 4 shows a case where the coordinate indicator is tilted with respect to the tablet surface, and points to the same pointing position 8 as in FIG. 3, but inside the coil 7.
There is no A. Since the coil 7 is located between the second grain and the third grain of the sense line 3, the voltages induced in the first grain and the third grain of the sense line 3 are not equal. Therefore, when the coordinate indicator is tilted, an error occurs in which the coordinate values move in the direction in which the coordinate indicator is tilted rather than the actually indicated position.

One method for correcting this error is to use a secondary peak. The correction method will be briefly explained with reference to FIG. Fifth
Figure fat is a distribution diagram of the induced voltage when the coordinate indicator is perpendicular to the Tablev plane. As shown in the figure, the maximum induced voltage is generated in the vicinity of the coordinate indicator, but local maximum values (secondary peaks) whose amplitude is smaller than the peak are also generated in the surrounding area.

This is due to the negative phase component of the coil.

If the coordinate indicator is vertical, the secondary peaks on both sides are equal. FIG. 5(b) is a distribution diagram of induced voltage when the coordinate indicator is tilted with respect to the tablet surface. When the coordinate indicator is tilted, the secondary peak on the tilted side becomes larger, and the secondary peak on the opposite side becomes smaller. The difference between the secondary peaks on both sides is used to correct the error due to the slope.

In order to read out the secondary peak, the conventional coordinate reading device scans a sense line in a square area including the area where the secondary peak can be detected, such as the sixth leap, and reads out the secondary peak.

[Problem to be solved by the invention]

In the conventional method of scanning sense lines in a square area including an area where a secondary peak can be read, the number of sense lines to be scanned is large. Accordingly, a large amount of processing time was required to detect the l coordinate.

Therefore, the present invention provides the minimum necessary coordinate calculation area and two
The purpose of this method is to scan only the next peak detection area, omit scanning of unnecessary sense lines, and perform scanning for coordinate detection at high speed.

Means for Solving Problem C] In order to solve the above problem, the present invention provides a coordinate indicator that indicates a coordinate reading point, a tablet that is electromagnetically coupled to the coordinate indicator, and a sense line installed on the tablet. In the coordinate reading device, the control section includes a scanning section that selects the sense lines one by one and extracts the voltage induced in the sense lines, and a control section that instructs the scanning section which sense lines to select. A scanning process that selects a sense line in a rectangular area centered around the sense line position where the sensor is located and reads the induced voltage, and a peak detection process that determines the peak detection sense line position where a peak is detected within the rectangular area. Then, from the peak detection sense line position determined by the peak detection process, a secondary peak detection position determination process is performed to determine the position where the secondary peak occurs, and the sense line position determined by the secondary peak detection position determination process is scanned. A secondary peak detection process was provided to read the secondary peaks.

[Effect]

In the coordinate reading device configured as described above, a minimum number of sense lines are scanned to calculate coordinates by scanning processing, and voltages induced in the sense lines are read out. In the peak detection process, the position of the peak detection sense line where the largest voltage is read out of the induced voltages read out by the scanning process is determined. The secondary peak position determination process determines a secondary peak detection position based on the peak detection sense line position determined by the peak detection process. In the secondary peak detection process, the sense line where the secondary peak is located is scanned and the secondary peak is read based on the secondary peak detection position, so unnecessary sense lines are not scanned and scanning can be performed at high speed.

〔Example〕

Embodiments of the coordinate reading device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a coordinate reading device according to the present invention. The scanning unit 4 scans the sense line 3 instructed by the control unit 5.
is selected, and the voltage induced by the coordinate indicator 1 is taken in and passed to the control unit 5. Each process within the control section 5 will be explained with reference to the flowchart in FIG. FIG. 2 is a schematic flowchart of the control unit, including scanning processing S1, peak detection processing S2, secondary peak detection position determination processing S3 and S2.
The present invention is realized by four processes including the next peak detection process S4.

(Scanning process sl) In scanning process S1, 0 lines (5 lines in this embodiment) of nx on one axis centering on the previously detected peak detection sense line position
n sense lines are scanned and the voltage induced on each sense line is read.

(Peak Detection Process 32) The peak detection process S2 detects peak detection sense line positions pax and Pa3' from which the maximum value is read out of the induced voltages in the rectangular area (nxn) read by the scanning process S1.
seek.

(Secondary peak detection position determination process 53) The secondary peak detection position determination process S3 is a peak detection process S
The peak detection sense line position Pa determined by 2
The sense line position where the secondary peak exists is determined by xSPay and secondary peak appearance positions Pol and Po2 located at a constant distance from Pax and Pay by experiment.

In this example, the sense line pinch is 6.35 mm, the coil diameter is 5 mm, and the height from the sense line to the coil is 4.5 mm.
mm, and Po1=3 and Po2=4.

According to experiments, it has been confirmed that the secondary peak is included in these two ranges. The formula for determining the sense line position where the secondary peak exists is as follows.

al= (Pax+Po1.Pay) a2= (Pax+Po2.Pay) a3= (Pax-Pol, Pa)') a4= (Pa
x-Po2. Pay) a5= (Pax, Pay+Po1) a5=
(Pax, Pay+Po2)a 7= (Pa
x, Pay-Po 1) ag= (Pax,
Pay-Po2) (Secondary Peak Detection Process 34) In the secondary peak detection process S4, the sense line position determined in the secondary peak detection position determination process S3 is instructed to the sequential scanning unit, and the induced voltage is extracted. The extracted voltage values are the voltage values (Vl and ■2, v3 and ■4) of each adjacent detection part l (a1 and a2, a3 and a4, a5 and a6, a7 and a8).
, v5 and v6, Vl and VB), and the larger voltage value is adopted as the secondary peak.

Normal scanning time per sense line is 150μse
Since 200 μsec is required from c, the scanning time of the conventional device is 9×9=81 lines, which is 12150 μsec to 162
00 μsec was required.

The scanning time of the coordinate reading device according to the invention is 5X5+8
= 495 for 33 lines (1!1sec to 6600μsec
Coordinate detection can be performed using

〔Effect of the invention〕

As described above, in the present invention, the secondary peak appearance position is determined from the coordinate values detected by the coordinate detection section, and coordinates can be detected at high speed because only the minimum sense line necessary for coordinate calculation and tilt correction is scanned.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a coordinate reading device according to the present invention;
Fig. 2 is a schematic flowchart of the control unit according to the present invention, Figs. 3 and 4 are explanatory diagrams for explaining the coordinate detection error caused by the 1st rotation of the coordinate indicator, and Fig. 5 is due to the tilt of the coordinate indicator. FIG. 6 is an induced voltage distribution diagram illustrating changes in the distribution of induced voltage, and FIG. 6 is an explanatory diagram of sense line scanning using a conventional scanning method. ...Coordinate indicator...Tablet...Sense line...Scanning unit...Control unit Sense line scanning range scanning processing Peak detection processing Secondary peak detection position determination processing Secondary peak detection processing

Claims (1)

[Claims] A) a coordinate indicator that indicates a coordinate reading point, b) a tablet that is electromagnetically coupled to the coordinate indicator, and c) a sense line laid on the tablet that selects one by one. , a scanning unit that extracts a voltage induced in the sense line, and d) a control unit that instructs the scanning unit which sense line to select, e) the control unit includes: A scanning process that selects a sense line in a rectangular area centered on the sense line position where the coordinate indicator is located and reads the induced voltage; g) a peak detection process for determining the position of the peak detection sense line where the peak detection sense line was detected; , find the position where a signal with an opposite phase to the peak (hereinafter referred to as a secondary peak) occurs 2
scanning of the coordinate reading device, including: a secondary peak detection position determination process; and h) a secondary peak detection process of providing the sense line position determined by the secondary peak detection position determination process to the scanning unit and reading the secondary peak. method.