JPH0287219A - Plotting picture input device - Google Patents

Abstract

PURPOSE:To remove fluctuation caused by the noise of analog electric quantity by sampling the analog electric quantity indicated by an (x) or (y) coordinate, with a time interval shorter than a prescribed time several times at a sampling time of every prescribed time and calculating an input position based on a mean value. CONSTITUTION:The title device is provided with an input pad 11 to output the respective coordinate values of the (x) and (y) coordinates indicating show the input position as an analog electric quantity and a control part 15 to sample the analog electric quantity indicating the (x) and (y) coordinates, outputted from the input pad 11 alternatively every prescribed time and to calculate the input position based on a sampling value. The control part 15 executes the sampling every prescribed time several times with the time interval, which is shorter than the prescribed time, and calculates the input position based on the mean value. Thus, the mean value is almost coincident or approximated with the analog electric quantity when the noise is not overlapped. Then, the fluctuation caused by the noise is eliminated.

Description

[Detailed description of the invention] (b) Industrial application fields The invention relates to a drawn image input device.

(b) As an input device for conventional technical drawing + fii image communication,
The Graphics Tablet is suitable because it allows arbitrary characters and figures to be input without a special πIIN.In recent years, the demand for inputting graphics into computers has increased, and various types of detection A drawing image input device based on the principle has been announced (Nikkei Electronics, No.
, 69, P, 79.1973).

FIG. 1 shows a conventional a#1 human power device using an input pad made of a resistive sheet, (1) is an input pad made of a single resistive sheet such as - (2iJ to (2n)).

(3i) ~(3n), (4i) ~(4m), (5I
) to (5m) are electrodes arranged along the four peripheries of the input pad (1), (6i) to (6n), (7i) to (7n)
, (8+) ~ (8m), (9 layers) ~ (9m) are the reverse current prevention diodes connected to the electrodes, and the shout is the I/V conversion channel switching circuit of the 4-power l output circuit. Each input terminal Xi, X2, yl, y2 is connected to a diode (61) to (4n
) Connected to the diodes 71) to (7n) arranged on the right side, the diodes (81) to (8m) arranged on the lower side, and the diodes (91) to (9m) arranged on the upper side. . Further, the switching circuit (10) switches the input terminals X1+X2, . Current HL input from yl, y2
The voltage yl-, y4 proportional to %H4 is outputted sequentially to the output terminal OUT.
Output to.

(1 is an input pen, (14 is a constant current source, and by bringing the tip of the pen (11) into contact with the input pad lj, the constant current source (from the figure is output, and the Kuden accent is the input pad ( l(, electrodes (2i) to (5m) and diodes (6i)
) to (9m) to the input terminals Xi, X2゜yl, y
2 will be input respectively.

Note that the current value i[ inputted at the input terminal xIK'' is the total value of the specific gravity flow values collected from the input pad !1+W poles (2+) to (2n) on the left side, and similarly ,y
The I current values 12 to i4 inputted to 2 are the electrodes on the right side (
3I) to (3n), the total value of the current values taken out from the electrodes (4i) to (4m) on the lower side and one pole (5I) to (5m) on the upper side.

In addition, since the above-mentioned human-powered band fl+ has a uniform resistance value, the current jet taken out from each pole (21) to (5m) is at the contact position of each electrode and the input pen tll). is inversely proportional to the distance 111 between each input terminal xt.

z2. The current values input to yl and y2 also change depending on the contact position.

(131 is a low-pass filter, and this filter weighs the voltage output from the channel switching circuit (10) and removes high-frequency noise by 1. (I41 is an A/D converter, and this converter is a low-pass filter The pressure value outputted from 7 is converted into a digital value and output.

Therefore, the digital value is proportional to the current value Ht~i4. α5) is a control section composed of, for example, a microcomputer, and the control section S includes various registers and controls the above-mentioned sections based on a built-in control program. That is, as mentioned above, the channel switching circuit +101
By controlling the input terminal X1mX2+y1. y
I pressures v1 to v proportional to the currents 11 to i4 input to 2
In addition to outputting the signal at a predetermined time interval, it also reads the digital @1 output from the A/[] converter in synchronization with the output at a predetermined time interval. (U calculates and outputs the coordinate information X and Y on 11.

Specifically, in the X direction on the intervening cupad (l)! When the distance between the poles is Lx, and the distance between the poles is 'f1 in the y direction, the distance between the poles is Ly.
Assume that the contact point P is large and comes into contact with the position P of iy from the lower end side ya pole. In this case, the resistance of the input pad (1) is uniform. Therefore, the input terminal xt, x2 channel switching circuit 1υ,
7M flow if input to 1 respectively, north of i2 is i l:
12=(Lx-1x): lx, and input terminal yl
, y2 to the channel switching circuit 1101, the north of the current i8.i+ is 18Hi4=(Iy-1y
):iy. Therefore, the left end example above is the array line of poles (2I) to (2n) and the lower end side "'ritfi<41) to (4m)"
If the origin is the point 0 at the lower left corner of the input pad (1), which intersects 1tt with the array 1 line of the input pad (1), the coordinates X and Y of the contact position P are )-11+I1
It becomes 1.

Therefore, when the distances mLx and Ly are set in advance, the control unit 051 outputs the absolute distance of the contact position P from the origin 0 as the coordinates X and Y based on the above (11). , when the above Lx and Ly are not set, simply calculate "il+i2...(III)""mB+i4...GV) and output the result as relative coordinate position information from the origin 0. The above x,
Calculate y'2.

In this way, in the conventional device, the rf! Input bad tll based on the current value It-it sampled every 1
(c) Problems to be Solved by the Invention Accordingly, the current output from the input pad +I) and the channel switching circuit (lO) Induction noise caused by human hands, power supply noise, external noise, etc. are easily detected in the analog electrical quantity such as the voltage output from the device.

For this reason, the above-mentioned low-pass filter 1131i is inserted on the circuit to remove the above-mentioned noise, but it is not possible to completely remove the noise with a certain filter (13) alone, and the External noise may be superimposed again on the line leading to the D converter (I41VC).As a result, the coordinates calculated based on the digital values output from the A/D converter are
There will be a slight deviation from the coordinates of the actual contact position on the input cover (1).

That is, when noise is superimposed on the voltage input to the A/D converter i+4)K, the input ? Direct pressure value V.

is unstable, as indicated by the broken line in Figure 3.

Incidentally, the solid line in FIG. 3 indicates the input voltage value Vo when the above-mentioned noise is not superimposed. Also, horizontal 1IqlI in Figure 3
indicates all the timings for sampling the output of the control unit (lω is the A/D converter 04), specifically, hal, χ2
．． ．． t8. Each timing of χ reef indicates the timing at which the control unit (16) reads the digital value of the next voltage value yt-V4, which is proportional to the current value 1x, B4 input to each input terminal xl+x2*y1+y2 of the channel switching circuit number. ing.

Therefore, for example, the voltage value ■ read at the timing of χ1
1 is actually inputted to the input end x1 from the input pad (1) and is slightly deviated from the voltage value v1 which is proportional to the nine current value 41.

As a result, even when drawing is performed on the input pad (1) as shown in FIG. As shown in FIG. 4(b), the straight line turned into a wavy line, which was undesirable.

B) Means for Solving Problem A This invention was made in consideration of the inventive point, and its structural feature is an input pad that outputs the coordinate values of the X and Y coordinates 4 indicating the input position as an analog electrical quantity. and a control unit that samples the analog electrical quantities representing x, yJl* outputted from the input pad at predetermined intervals alternately and calculates the input position based on the sampled values, and a drawing image input device comprising ft. In the apparatus, the control unit controls the analog signal "1 volume? Upper CK!" indicating the X or ypM mark at the time of sampling at each predetermined time to sample multiple times at time intervals shorter than the predetermined time, and based on the average value. The above human power 13χ
Place? It's about calculating.

(e) As is clear from Figure 3, the shift in the analog electrical quantity when noise is superimposed is centered on the analog electrical quantity (?voltage) when no noise is superimposed. This is caused by non-periodically wandering to the side.

Therefore, according to the above configuration, the average value is approximately equal to, but approximates, the analog electrical quantity when no noise is superimposed.

The only difference between the embodiment and the conventional device described in FIG.

FIG. 2 is a flowchart showing the control operations of the control unit 151 according to the present invention, and the operation of this embodiment will be explained below based on the flowchart.

First, in Step Sl, it is determined whether the input pen (11) is in contact with (down) the input pad (1) or not. Prayer'tlJ setting is input pad (1 (,
Only when the pen is brought into contact with the input pen (using the fact that current flows through the river), a detector (not shown) detects the presence or absence of the current.

When contact with the pen is detected in step S1, step S2 is then processed. In the S2 step of praying, "0" is set in the change register CH, and in the continuation<53 step, the contents of the rejecting register CH are incremented.

The process then proceeds to step 84, in which the channel switch-tBuol determines which input x1. x2. y1. Current 11-H+ manually applied from y2
A signal indicating whether to output a voltage vlzv41 proportional to the change register CH is output based on the contents of the change register CH.

Specifically, CH=1... A signal for outputting a voltage Vl proportional to the current 11 inputted from the input terminal x1 CH=2... A signal for outputting the voltage Vl proportional to the current 11 inputted from the input terminal x2. Signal for proportional voltage v2tl-Takata CH=3...Input from input terminal y1? "Signal CH=4 for outputting a voltage v8 proportional to the current 18...A signal for outputting a voltage v4i proportional to the current i4 input from the input terminal y2 is output, respectively.

At step <55, the timer starts, and then enters a standby state at step S6.

In the waiting state #g, the voltage output from the channel switching circuit UO+ based on the selection signal in step S4 is passed through the low-pass filter (Ii?) to the A/D converter (1
4I, it waits until the output of the low-pass filter 0:1 becomes stable. Further, since the time required for the desired output to stabilize is determined by the circuit time constant of the low-pass filter (13), the waiting time can be set in advance according to a predetermined time constant.

When the above S6 step ends T, the A/D converter t14
)K is supplied with a stable voltage through the low-pass filter 01. Therefore, during the subsequent processing of step S7, VC is A/D
Since the converter 04) outputs a digital value corresponding to the stable voltage, in a certain step S7, the digital value is sampled eight times at a sampling period of 40 μs.

At step d<88, the average value of the eight digital values sampled at step S7 is calculated and held.

Specifically, when the content of the variable register CH is "1", the above-mentioned value is stored in the holding register PIK, and the content of the above-mentioned register CH is r2J, r3J or "4".
When , the dog floor holding register P2. Stored in PR or P4.

Next, step S9 is processed, and at a certain step it is determined whether the content of variable register C)T is "4" or not, and if not, the process proceeds to step S1υ. S.I.
In the O step, it is determined whether the time count value started in the S5 step is 1 ms or more, and if it is not 1 ms or more, the S10 step is repeated for prayer, and when it reaches 1 ms, the process returns to the 53 step. If it is determined in step S9 that the contents of the register CH are "4", the process proceeds to step S11. Holding register P! stored in step US8 in pray step! ~ Based on the contents of P4, coordinate information X of the contact position of the input ben (Ill) on the input pad (1)
, Y are calculated and output.

Specifically, in IIC, digital values of voltage values yt to V4 corresponding to currents 41 it to i4 are stored in the holding registers P1 to P4, respectively. Therefore, in step S11, the coordinate # and the information X; Yi are calculated and output based on Equation 52. In addition, in the above formula (V) (Vl), r(Pn) (n=1
~4)'' indicates the contents stored in the holding register Pnvc.

When the processing of the Sll step is completed, the processing returns to step 81.

In this way, on the nut shelf side, when the input pen (11) is brought into contact with the input pad (1), the loop consisting of steps 83 to 810 is repeated four times every f1ms, and the channel is Each input terminal X1 of switching circuit jR1101
, x2. Digital values of voltages corresponding to current values 11 to i4 inputted from yl and y2 are read and held. Also,
The digital value held in each loop is the average value of eight samples sampled at a sampling period of 40 μs in 87 steps. Therefore, the coordinates X and Y calculated in step S11 are the input pad (1).
Even if noise is superimposed on the analog electric quantities of current and voltage on the line from A/D converter A to A/D converter A, does it match what would be calculated if no noise was superimposed? Or approximate this.

As a result, even when the alphabetic character rAJ is input on the input pad 11 as shown in Figure 4 (aJ), the straight line does not change to a wavy line and is output as in the conventional case.

In addition, on the Kinomi style side, it is configured to read the current ir-i4t-1ms corresponding to the position information from the manual pad (9) at predetermined time intervals, but the fring time is not limited to this. In addition, the sampling period and the number of sampling times are not limited to those in the above embodiments, and may be in the range of (sampling period) x (sampling number - 1) (predetermined time).

(g) Effects of the Invention According to the present invention, fluctuations due to noise in the analog electrical quantities output from the input pads corresponding to the input positions can be removed simply by increasing the sampling times at of the control unit for each electrical quantity. Therefore, since there is no need to make any changes to the circuit when applying the present invention to the conventional device, the present invention can be easily applied to the conventional device.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the image input device, Fig. 2 is a flowchart showing an embodiment of the present invention, and Fig. 3 shows the variation #J of the voltage input to the A/D converter in Fig. 1. Graphs shown in FIGS. 4(a) and 4(b) are schematic diagrams for explaining problems in conventional devices. m...input pad, (IQ...I/V conversion channel switching circuit,・Control unit. Applicant: Sanyo Electric Co., Ltd. (1 other person) Attorney: Takuji Nishino (1 other person) Figure 2

Claims (1)

[Claims] (1) An input pad that outputs each coordinate value of the x and y coordinates indicating the input position as an analog quantity of electricity, and an analog quantity of electricity indicating the x and y coordinates output from the input pad alternately at a predetermined time interval. A drawing image input device comprising: a control unit that performs sampling and calculates the input position based on the sampling value; A drawn image input device characterized in that the input position is calculated based on the average value of the input position by sampling the input position a plurality of times at time intervals shorter than the predetermined time.