JPS6019833B2 - digitizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digitizer that determines the position of a cursor on a tablet using an optical coupling method.

Some digitizers are suitable for deriving digital data from analog displays such as drawings, but there are various types depending on the method used to measure the position of a cursor or pen, which is a positioning element.

Typical examples include mechanical, electrostatic, electromagnetic, acoustic, and optical means. Among these, the optical digitizer is
Usually, a light emitting element is attached to the cursor, light receiving elements are arranged all over the tablet, and the position of the cursor is determined by detecting the light receiving element that receives light from the cursor. However, since the resolution is determined by the spacing between the light-receiving elements arranged on the tablet, there is a problem that high resolution cannot be expected. In view of these points, it is an object of the present invention to provide an inexpensive digitizer that can easily realize a high resolution chamber with a relatively simple configuration.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram showing the main part of an embodiment of a digitizer according to the present invention. In the figure, a tablet 11 is a work board on which light emitting elements 12x and 12Y are arranged. The light emitting elements 12x and 12Y are arranged at equal intervals, respectively.
The light-emitting elements 12x and 12Y are arranged orthogonally to each other. 21x is light emitting element 1
2x,~12xn are sequentially scanned and driven one by one.
The axis switch circuit 21Y similarly connects the light emitting elements 12Y, to 1
This is a Y-axis switch circuit that sequentially scans and drives 2Yn one by one.

The switches 21x and 21Y each have an input terminal 23x.
, 23Y, a current is sequentially applied to each element in synchronization with the pulse P2 applied to the strip-shaped elements to cause them to emit light. Fig. 2 is a diagram showing how the light emitting elements are driven. Fig. 2A shows how the blinking light from the elements in a vertical row travels in the horizontal direction due to scanning by the X-axis switch circuit 21x, and the opening in the figure shows the Y-axis switch. This figure shows how the circuit 21Y causes blinking light from a horizontal row of elements to travel in the vertical direction. Note that since light emitting elements are generally not transparent, the vertical and horizontal light emitting elements do not overlap, and the light emitting element at the intersection of the vertical and horizontal columns is connected to either the x-axis switch circuit 21x or the Y-axis switch circuit 21Y. It is also possible to blink. FIG. 3 shows the pulse P2 applied to the input terminal 23x and the light emitting element 12x, ~
12xn drive timing is shown, switch circuit 2
1x is also driven by a pulse P, which is input to the input terminal 22x, so that the light emitting elements are sequentially driven as shown in FIG. The pulse P. and P2 are obtained by appropriately dividing the reference clock of the oscillator 25 in FIG. This pulse is obtained by dividing the pulse P, into 1'2 tubes by the frequency generator 27. Numeral 31 is a cursor that can be manually positioned on the tablet 11, and the light receiving element 32 is located in the center of the cursor.
It receives the traveling wave on the tablet, converts it into an electrical signal, and sends it to the amplifier 41.

The amplifier 41 has a tuning function and has a high amplification factor only for the blinking frequency of the light emitting element. A rectifier 42 has the function of rectifying the output of the amplifier 41.

A bandpass filter 43 extracts only the fundamental wave of the output of the amplifier 41.

The output of the amplifier 41 has a waveform as shown in FIG. 5A, and its generation time corresponds to the separation distance of the cursor 31 from 12x, (or 12Y,) at the end loop. The opening in the figure is the output of the rectifier 2. 44 is a counter that detects the time of this occurrence, and it crosses zero when the output signal of the filter 43 changes from positive to negative from the start of driving the light emitting element 12x (or 12Y). The time it takes to reach this point is measured by Crotz counting. In this case, the point that crosses zero is shifted by 90 degrees from the position of the cursor 31, so a drive signal generated at a phase shifted by 9 degrees from the light emitting element driven first is applied to the counter 44 as a start pulse to count the clocks. That's what I do. The operation of the present invention in such a configuration will be described next.

First, the digitizing operation regarding the x-axis will be described. The pulse P obtained by the first and second frequency dividers 26 and 27,
, P2, the switch circuit 21x switches on the light emitting elements 12x, , 12 in synchronization with the pulse P2 as shown in FIG.
x2, . . . 12xn are sequentially driven. As a result, the flashing light emitting band shifts as shown in FIG. Obtain a pulsating flow signal as shown in . Next, the fundamental wave of the pulsating flow signal is detected by the band-pass filter 43 to obtain a sinusoidal output as shown in FIG. 21x output end 2
The oscillator 2 is activated by the start pulse Ps given by 4x.
Start counting the clocks from 5, and then the fundamental wave will start counting from the 6th clock.
The counting operation continues until it crosses zero as shown at the beginning of the figure. The count value of the counter 44 at this time is the cursor 31
Therefore, the position of the cursor 31 on the tablet 11 can be read based on this count value. The position can also be determined in the Y-axis direction by the same operation as described above.

In this way, the position coordinates of the cursor 31 can be determined.

However, the errors that occur in such a digitizer are primarily dependent on the filter 43. That is, if the center frequency of the filter changes due to temperature changes, changes in parts over time, etc., the phase of the passing frequency changes, which directly causes a measurement error in the cursor position. In order to solve this problem, for example, as shown in FIG. 7, an analog switch 51 is inserted and connected between the amplifier 41 and the rectifier 42, and the detection system can be calibrated by simulated input. In such a configuration, as shown in FIG. 8, the switch 51 is switched during position measurement of the cursor 31 to set the calibration mode, a simulated input for calibration is input to the rectifier 42 via the switch 51, and the time difference is measured. By calibrating the detection system including the filter 43, the actual measured value of the cursor position can be corrected. In this case, it is not necessary to set the calibration mode every time after measuring the cursor position, and the calibration mode may be set at an appropriately thinned interval in consideration of the stability period of the detection system. FIG. 9 shows the measurement error with respect to the position of the cursor, and the error is small at the center of the digitized area, but becomes rapidly large at the edges.

This is because the number of light emitting elements is limited, so that a phase shift occurs between the peaks of the signals before and after passing through the filter 43, which causes an error. FIG. 10 is a block diagram showing an embodiment of the digitizer that can expand the small error range, so-called usable range, shown in FIG. 9, except that a variable threshold rectifier circuit 61 is inserted and connected in place of the rectifier 42. are the same as those in Figure 1.

The output waveform of this rectifier circuit 61 is shown in FIG. This figure shows how to remove low-level signals on both sides, which are information from light-emitting elements located outside the cursor, by appropriately increasing the threshold level. By such removal, the influence of the finite number of light emitting element rows can be removed, and as shown in FIG. 12, virtually the entire area becomes usable. In the embodiment, the output voltage of the filter 43 is always kept constant,
2 is a configuration diagram of a digitizer that can measure a cursor position while keeping the threshold level of a rectifier circuit 61 constant. FIG.

That is, a peak voltage detector 71 and a comparator 72 are added to the digitizer of FIG. 10 described above, and the amplifier 41 is further replaced with a variable gain amplifier 41a. This peak detector 71' detects the peak of the output voltage of the filter 43, and the comparator 72 compares this with a comparison voltage. Based on this comparison result, the gain of the variable gain amplifier 41a is controlled to keep the output voltage of the filter 42 constant.
Therefore, the magnitude of the signal input to the rectifier circuit 61 is always constant, and even if the cursor rises above the surface of the tablet 11 and the output signal becomes small, the threshold level remains constant. Can measure position. FIG. 14 shows another embodiment, which is the same as that of FIG. 10 except that a threshold control circuit 81 is used.

This threshold control circuit 81 determines the threshold level in relation to the peak value output of the band pass filter 43. For example, when the peak value of the filter 43 becomes 1/2, the threshold level of the rectifier circuit 61 increases. It is also set to be 1/2 times as large. As a result, the influence due to the finite nature of the light emitting element can be removed as described above. The resolution of the digitizer mentioned above is
It is mainly determined by the short-term stability of the filter 43.

This short-term stability refers to phase fluctuations on the order of several tens to hundreds of kHz, and slow phase changes such as drift can be removed by adopting the calibration mode described above, but this short-term stability is generally measured by period measurement. There is no reasonable solution other than doing this several times and averaging it. for example,
To measure 36 yards with a resolution of 0.1 skin, the short-term stability of the phase must be 0.10 or less, but this is quite difficult to achieve. FIG. 15 shows a configuration for solving this problem, and the difference from FIG. 14 (also includes FIGS. 10 and 13) is that mode-variable switch circuits 211x and 211Y are used to drive the light emitting elements. By using . be. In addition to the functions of the switch circuits 21x and 21Y described above, the circuits 21 1x and 21 1Y have a mode in which the same current can be simultaneously applied to a plurality of light emitting elements spaced apart by a certain distance.

Figure 16 shows this situation. In mode A (fine measurement) shown in Figure 16, the same current flows through N light emitting elements in the measurement range, and in mode B (rough measurement) shown in Figure 16, one current flows through N light emitting elements in the measurement range. It is shown that current flows only through the light emitting element. The waveform shown by the broken line in the figure shows the output of the filter 43, and is in mode A.
In this case, the range to be measured by the phase change of 3600 is 1'M of mode B, and therefore the resolution can be improved by that much. However, in this case, mode A
As is clear from Figure 16A, they cannot be distinguished from each other at positions with a 360° phase shift.
Mode B makes this distinction.

However, mode B does not require particularly high resolution since it is only necessary to be able to make the above distinction. FIG. 17 shows an example of the operation transition. In particular, the above-mentioned calibration modes are mixed, and in X-axis position measurement, calibration mode → mode A → mode B, and in Y-axis position measurement, calibration mode → mode A →
It is shown that the position measuring operation is performed in the order of mode 8. Furthermore, in the digitizer shown in Fig. 15,
The frequency of the output waveform of the filter 43 in mode A is N times that in mode B.

Therefore, it is necessary to prepare another set of detection systems suitable for N times higher frequency signals as a detection system, but in order to simplify the system, one input pulse P2 is added to the switch circuit only in mode A. By configuring the input data to be divided into 1/N parts, the detection system can be set as one set. In addition, although the example shows a case in which a light emitting element is arranged on the tablet and a light receiving element is mounted on the cursor, the invention is not limited to this, and conversely, the light receiving element may be similarly arranged on the tablet and a light emitting element is mounted on the cursor. You may.

In this case, the light emitting element of the cursor is driven by the pulse P output from the first frequency divider 26 and projects a blinking light onto the light receiving element on the tablet, and the x-axis switch circuit 21x, Y
The axis switch circuit 2.1Y is configured to perform the role of multiplexing the output from the light receiving element and sequentially connecting it to the amplifier 41. As explained above, according to the present invention, an output proportional to the position can be directly obtained through relatively simple synthesis, and there is no need for interpolation or nonlinear correction. Therefore, it is possible to realize a high-speed and inexpensive digitizer. can.

Additionally, even if the cursor and tablet are spaced apart and the output of the sol becomes smaller, the phase is detected, so the magnitude of the output will not cause an error, making it possible to create a digitizer that is less susceptible to environmental conditions. can.

Furthermore, by calibrating by applying a simulated input, it is possible to easily remove the influence of phase changes caused by drift in the detection system, and the density of light emitting elements, etc. can be easily removed by fine and coarse measurements using modes A and B. This has great practical effects, such as the ability to easily improve resolution without increasing resolution.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main part of a digitizer according to an embodiment of the present invention, FIG. 2 is a diagram explaining how the light emitting element is driven, and FIGS. 3 and 4 are diagrams showing the timing of driving the light receiving element.
FIG. 5 is an output waveform diagram of the amplifier 41, and FIG. 6 is a diagram of the output waveform of the amplifier 41.
Figure 7 is a diagram for explaining the operation of step 3, Figure 7 is a diagram showing the main parts of the part adopted when implementing the calibration mode, Figure 8 is an operation transition diagram when implementing the calibration mode, Figures 9 and 12
The figures are diagrams showing the relationship between the cursor position and error on the tablet, Figure 10 is a diagram of another embodiment of the present invention, Figure 11 is a diagram for explaining the function of the rectifier circuit 61, and Figures 13 to FIG. 15 is a diagram showing still another embodiment of the present invention, FIG. 16 is a diagram for explaining mode A and mode B, and FIG. 17 is a diagram for explaining mode A and mode B.
7 is an operation transition diagram of the digitizer shown in FIG. 6. FIG. 11...Tablet! 2x, 12Y...Light emitting element, 21x
, 21Y, 211x, 211Y...switch circuit, 25.
... Oscillator, 26, 27... Frequency divider, 31... Cursor, 32... Light receiving element, 41, 41a... Amplifier, 42... Rectifier, 43... Band pass filter,
44... Counter, 51... Analog switch, 61... Rectifier circuit, 71... Peak voltage detector, 72... Comparator ~ 8
1...Threshold control circuit. Figure Key Figure N Key Figure 3 Belt Figure Figure 5 Figure 6 Figure 7 Silk 8 Figure Silk 11 Figure 9 Figure 12 Figure 16 Figure 17 Figure ○ Crocodile Figure h Key Figure Mountain Carp

Claims (1)

[Scope of Claims] 1. Frequency dividing means for dividing the frequency of a reference clock to obtain a clock pulse of a predetermined frequency; a work plate on which a plurality of light emitting elements or light receiving elements formed in a strip shape are arranged; When the light emitting elements are disposed toward the work plate, a plurality of light emitting elements on the work plate are linearly scanned in synchronization with the pulses given from the frequency dividing means to generate a traveling wave of blinking light. The traveling wave is detected by a light-receiving element attached to a cursor that can be positioned on the work plate, and conversely, when the light-receiving element is placed toward the work plate, the light-emitting element is attached to the cursor. Traveling wave detection means for generating blinking light from a light emitting element, linearly scanning a plurality of light receiving elements arranged on a work plate in synchronization with pulses given from the frequency dividing means, and detecting the blinking light. , a detection means for detecting the output signal of the traveling wave detection means, a band pass filter that passes only the fundamental wave of the output from the detection means, and a counting operation is started by the signal from the traveling wave detection means. A counter configured to stop counting operation based on an output signal from a bandpass filter and counting the clock is provided, and the position of the cursor on the work board can be detected from the counted value of the counter. Features a digitizer. 2. Claim 1, characterized in that the light-emitting elements or light-receiving elements arranged on the work plate are arranged orthogonally to each other so that two-dimensional coordinates can be read.
Digitizer as described in section. 3. The digitizer according to claim 1, wherein the digitizer is configured to configure a detection system while measuring the position of the cursor. 4. The digitizer according to claim 1, wherein the detection means is configured to be able to rectify at an arbitrary threshold level as appropriate. 5. Claim 1, characterized in that the detection means is capable of amplifying and controlling the input signal in relation to the output of the bandpass filter and rectifying it at a constant threshold level. Digitizer as described in section. 6. The traveling wave detection means is further configured to simultaneously drive the light emitting elements or light receiving elements on the work plate at regular intervals, so that the cursor position can be measured by fine measurement and coarse measurement. A digitizer according to claim 1, characterized in that: