JPS6147502A - Touch signal detection circuit - Google Patents

Abstract

PURPOSE:To detect a highly accurate touch signal by removing the low frequency component containing in a probe signal, by performing the detection of the touch signal based on the variation absolute value at the time of contact by removing the low frequency drift component contained in the probe signal. CONSTITUTION:A sample hold circuit 44 outputs the output 102 of a low pass filter as it is in a usual state and a reference value 104 is same to a probe signal 100 in such a state that a probe is not contacted with an object to be measured and, therefore, a differential operator 46 certainly removes the variation of a zero level. When the probe is contacted with the object to be measured, a high frequency variation receives delay by a low pass filter 42 and the reference value 104 being the output of a sample hold circuit 44 takes a value different from the probe signal 100 and a variation absolute value 106 is outputted from the differential operator 46. The variation absolute value 106 is compared with a preset threshold value Vth by a comparator 48 and, when said variation absolute value 106 exceeds the threshold value Vth, a touch signal 108 is outputted.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a touch signal detection circuit, particularly a touch signal detection circuit that outputs a touch signal with less detection error by shaping the waveform of probe No. 113 that includes a low frequency drift component. The present invention relates to an improved tap signal detection circuit that can be used.

[Prior Art] In addition to three-dimensional coordinate measurement, it is desired to accurately detect a shoe f1 such as a tap signal probe in contact with a fixed object such as i11!I!.

As is well known, in the F′f-standard measurement revision, P1]-
The coordinates of the swool of each axis when the probe contacts the object to be measured are read and memorized, and based on this, each measurement point of the object to be measured is determined. Contact 1: If there are variations in the tap signals output from the probe, this will appear as an error.Therefore, regardless of the contact state between the various measuring strips 1'1 or the probe and the object to be measured, - Touch signals must be output with a certain minute delay.

Conventional general touch signal probes use the inclination or movement of the stylus that occurs when it comes into contact with an object to be measured to make the contacts r and +t, and generate electrical on/off from the contacts. However, with touch signal probes using this contact method, the contact state of the contacts is unstable and picks up noise, and the signal detection is directional, so it is not always possible to achieve high accuracy. had the disadvantage of not being able to detect signals.

In recent years, a probe using another electrical detection water droplet instead of the conventional contact point has been put into practical use in the Touch No. 13 probe, which has significantly improved the IZ reliability of touch signal detection.
It also enables highly accurate detection.

For example, a piezoelectric element is known as this German detection water element. A touch signal 1q is generated using a piezoelectric voltage generated at 1q.

In addition, devices that utilize the piezoelectric effect of such piezoelectric elements as a piezoelectric effect that generates a shear force different from the compressive force (tension) described in 11a have recently attracted attention, and this J: una is used as a touch signal probe. It has now been discovered that obtaining a signal at shear forces is of great advantage in improving its efficiency.

As mentioned above, in recent years, it has become possible to detect signals with high sensitivity using piezoelectric elements and other devices, but these types of elements are themselves island impedance elements and require a preamplifier for impedance conversion in the detection circuit. As a result, the probe signal received from the piezoelectric element and preamplifier contains a low-frequency trit component based on the ambient temperature or preamplifier characteristics, and the changes that occur when the stylus contacts the probe signal immediately after the signal processing. There was a drawback that the waveform shaping process to obtain the absolute value of
No. 1 and f, probe 1 to detect 188 of 14.
, i,%! : 1i (When comparing
In some cases, it is necessary to output an absolute value between signals, but in such cases, the error in the O level causes a non-negligible drop in detection accuracy.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned conventional problems.The first objective is to eliminate the influence of low frequency drift and to make the probe the optimum standard for the problem. Give the value, and to this, with Jζ,
i-Bud contact with the measured object VIJ! Another object of the present invention is to provide an improved touch signal detection circuit capable of detecting the absolute value of change output and detecting a touch with high accuracy based on this.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method in which the low frequency drift component contained in the probe signal and the probe are
f! II'i Note that there is a significant difference in the frequency components due to the rise of the change when the waveform contacts an object, and that the steep rise frequency has a higher frequency than the low frequency drift component. , Characteristics 1-7 are that the probe signal itself is used as a reference value.

For this purpose, in Suikomei, the probe signal is converted to the reference 1fi by a low-pass filter and a 1 non-pull small circuit, and this ';'s 'l' fL+ and the probe signal are differentiated. The absolute value of the change in contact 1 is calculated.

The above-mentioned low-pass filter passes the low frequency drift (1 to 1) as it is, but has a steep rise (7). , 11, Calibration of probe signal and reference value f,
2J: Touch signals can be easily detected.

The absolute value of the change 11/j L,'L, which is the differential output, is compared with the predetermined threshold -1 and the absolute value of the change exceeds the threshold (11°1), and a touch signal is output. Then, this touch signal is given as a trigger signal to the 1-roller, and the non-pull hold circuit and low-pass filter are applied to the control signal from the 1-roller. Furthermore, in JT Liao, the sample hold is rimbling 1' when tap No. 1g is detected.
At the same time, the cut-off frequency of the low-pass filter is switched to a high level, so that it has a characteristic that allows the contact change component of the probe transmission to pass through as it is without giving any distortion. J: So, the probe is measuring 8 (J after 1) IJ? s) non-g
It is possible to avoid the occurrence of 1t)3.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on IS drawings.

FIG. 3 shows a touch signal detection circuit to which the present invention is applied.
A two-dimensional measurement (simplified configuration) is shown, with a probe 1 movable in the X, Y, and Z axes.
J3 is equipped with a touch button 12 that can be moved in all directions.
Then, the scale coordinates of each axis are read by using this Kudge welding bow while keeping this melting layer 12 in contact with the object 14 to be measured.

7'rl-710 f, tX axis II i? i AT
16, Y 4111 piezoelectric element 18 and 7-axis FF electric element 20 are arranged sequentially in 'A layer' (13, + Ij 5f hyperactivity of stylus 12 is electrically connected to each piezoelectric element 16 to 20. The piezoelectric elements 16-20 in this embodiment use the piezoelectric effect caused by the shearing force (13), and as a result, a good The projection sensitivity is set to the right, but J3 is in the - direction, and the piezoelectric effect changes the direction to the movement of the touch 3112.
In general, a piezoelectric element exhibits a highly sensitive detection characteristic for shearing along the polarization direction, but in a direction perpendicular to this, the detection sensitivity of 2- is significantly reduced.

Therefore, in the tap signal 8 detection circuit 22, the piezoelectric elements 16 to 16 are arranged along respective specific detection directions.
By combining the 20 outputs, the movement of the stylus 12 in all directions is simulated with almost the same delay characteristics.

Touch No. 13, which is the output of the cudge signal detection circuit 22, is supplied to the seat (sign reading circuit 24) and indicates the corrected position on each axis of the probe 10 (X scale 26, Y scale 2).
8. The coordinate 1 axis at the time of contact with the Z scale 30 is read and stored in the register 32.

At -1), the output of the register 32 is sent to the computer 34, and the coordinates of the measurement point are displayed on the display 36 in accordance with the predetermined operation. I can do it.

According to the present invention, the Kudjiye signal detection circuit 22
1) Shape the buoy No. 3 to the desired touch signal to each piezoelectric element 1G.
Village 1. (15) l:E of this touch signal detection circuit
The formation for the - axis of the will is shown in FIG.

Piezoelectric element, 1 row concave X-axis piezoelectric cord 16 has 11 sensitivity
It can be considered as an impedance sensor element T, and its output is impedance-converted by a preamplifier 110 and output as a probe signal Q100.

Therefore, this probe signal 100 contains a trit component of about 1/100 to IZ, which is a low frequency drift due to the characteristics of the piezoelectric element 1G or preamplifier 4o. ;= tea + Even if you perform a difference calculation such as direct and return the change output at the time of contact to 19, the O level will fluctuate, so the change absolute Takeda]]
However, it contains a huge error Z-.

For this purpose, in the present invention, the probe Shingetsu 100
L1- is characterized in that it forms a reference 1l17 for live ammunition (using itself).

Hereinafter, the operation of the 11'j U+b''J configuration in the embodiment of FIG. 1 will be explained with reference to the waveform diagrams of each part in No. 2!7!.

The probe signal 100 in FIG. 2 is at time 1. At d3, blow 1 came into contact with the object to be measured! It exhibits a sharp rising characteristic, and at 5 increments 1 (L, 1), the probe moves away from the object to be measured, so the signal value shows a falling characteristic.

Note that in the figure J3, a fine fluctuation component is shown in the signal 100 in order to clearly show that the probe signal 1oo includes a low frequency drift component, but in reality, this fluctuation component is The wavelength changes are sufficiently larger than those shown in the figure, and the period is never as short as this.

The characteristic feature of the present invention is that the probe signal 10
0 is the low pass filter 42 and sample hold circuit 4
This reference value 104 and the probe signal 100 are converted to a reference value 104 through a difference calculator 4.
The difference is stopped by 6 and output as the absolute change IU 106.

The low-pass filter 42 has a contact port with a steep rise that allows the low-frequency drift l-component to pass through as it is.
For example, the cutoff frequency on the low side is set to 1H7 in order to provide a predetermined delay for the change in 1, and if such a low-pass filter characteristic /J11 is used, the output will be 10
2 has an output as shown by the chain line 102- in FIG. However, according to the present invention, the low-pass filter 42 has not only the cutoff frequency on the low side but also the cutoff frequency on the high side, for example, IK I-I Z
At such a high cutoff frequency, the low-pass filter 42 does not give a Kawato characteristic to the high frequency change at the time of contact, but merely has an amplification factor of 1. It functions as an amplifier and outputs the probe signal 100 as it is.

In the present invention, as described later, probe contact start time 1. A touch signal is output at time t2 delayed by Δt from
2 is switched to the high frequency side, and as a result, the low-pass filter output 102 has the same waveform as the probe signal 100 after time t2, as shown by the solid line in FIG.

The sample hold circuit 44 outputs the low-pass filter output 102 as it is under normal conditions, and when the probe and the object to be measured do not contact each other, this base 11ul straight 1
It is clear that 04 is the same as probe signal 100.

Therefore, the difference calculator 46 does not output any 1g signal from the Ut contact side of the probe, and from this, there is a low frequency drift component, and it is difficult to reliably remove the O level fluctuation caused by this. It's possible to yell.

On the other hand, when the probe comes into contact with the object to be measured, as described above, this high frequency changing component is passed through the low-pass filter 42.
As a result, the output of the sample-and-hold circuit 44, W +−1ζfiff 1 Q4
, whose f:l'f is different from the ``b1''-b signal 100. Therefore, the difference calculator 46 calculates the absolute change (direct
06 is output. Then, the absolute value of this change is 106 (
The next comparator 48 has J5 and the threshold (ii'
J, V th is compared with this threshold value V t
h L; J: A predetermined constant 1fl, the second
(as shown in the figure), when the change absolute 1 straight 106 exceeds this threshold la V th, that is, 11. ), J3 outputs a touch signal 108 at clock [2].

When the low-pass filter output is virtual 1icf 102-, the absolute change l1 which is the output of the difference calculator 46
1106 also becomes the virtual value 106' shown by the chain line in FIG. 2, but in reality, as mentioned above, the low-pass filter 7I
What is more important is that the sample-and-hold circuit 44's 1t(q value 104 is at time L2 at J3 and subjected to rimbling, so from time 2 onwards, the absolute value of the change is 106). indicates a waveform as shown by a solid line.

The absolute value of the change 100 indicates the absolute value of the piezoelectric voltage based on the shearing force of 1 g from the intensifier 16 when the stylus 12 of the probe 10 comes into contact with the object to be measured 14. While the stylus 12 is in contact with the object to be measured 14 due to the holding circuit 44,
The waveform is similar to the probe signal 100, and from this, time 1. , the aforementioned threshold Ki is set again at n, y time t before I by Δ1-'.
V th is crossed, and at this stage the touch signal 108 returns to O level.

In the present invention, the touch signal 108 is transmitted from the controller 1 to the roller 5 at time 2 when the tap signal 108 is output.
0 as a trigger signal to the controller 501.
At this point, the number hold circuit 44 is placed in the 1 numbering state, thereby making the fall of the touch signal 108 dependent only on the waveform of the absolute value of change 106.

Also, at time 2, the controller 50 simultaneously increases the characteristics of the low-pass filter 42 by 1 on the descendant region side, and outputs 1
06 is almost the same as the probe signal 100. As is clear from the low-pass filter output 102 in FIG. 2, this characteristic switching is possible even when the probe stylus leaves the object to be measured.
may provide a sufficiently good delay time, for example several seconds, to the probe signal 100, and in such a case, the delayed low-pass filter output 102 of J3 after reaching the time tu may cause unnecessary and 1-(g
″;・J may appear. To prevent such a situation, the characteristics of the low-pass filter 42 are set by one convex on the high frequency side along with the number hold.

Therefore, according to the present invention, the false touch signal described above will not be output.

As described above, according to the present invention, the differential pii 46 outputs [, 1 change absolute 11fr 106, which is sent to the comparator/18 to set the desired threshold lii:
By comparing J' with t, an extremely stable tap that removes the low frequency drift contained in the probe signal M100 can reduce ['I08 by 1!7.

After time 3 when the touch signal 108 disappears, the controller 50 supplies a reset 1- signal to the low-pass filter /I2 and the thimble hold circuit 44, and
Switch the characteristics of the lEI user to the low frequency side, and also
- Cancel the mode.

[Effects of the Invention] As explained below, according to the present invention, it is possible to remove the low frequency components contained in the probe signal and detect a touch signal with a high vJ degree, thereby achieving high accuracy. The measurement function can be performed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a preferred embodiment of the touch signal detection circuit according to the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, and FIG. It is an overall schematic explanatory diagram of a state applied to a measurement object. 10... Probe, 14... Measured object, 16.18.20... Piezoelectric element, 22...
Touch 1gg detection circuit, t+O-°° free amplifier, 42...Low pass filter, /14...Return hold circuit, 46.
... 72 performance f5 unit, 48 ... comparator, 50 ... controller, 100 ... probe signal. 102...[1-Bass filter output, 104
... Base t%I direct, 106 ... Absolute value of change, 108 ... Touch signal.

Claims (1)

[Claims] (1) In a touch signal detection circuit that shapes a probe signal including a low-frequency drift component and outputs a touch signal when the probe contacts a non-measurable object, the low-frequency drift component of the probe signal is passed through and A low-pass filter that provides a predetermined delay characteristic for steep changes; a sample-hold circuit that holds the output of the low-pass filter at a predetermined timing; and a sample-hold output that calculates the difference between the probe signal and the sample-hold output. A difference calculator outputs the change at the time of contact included in the probe signal as a reference value as an absolute value, and compares the change absolute value output of the difference calculator with a predetermined threshold value to calculate the change absolute value. a comparator that outputs a touch signal when exceeds a threshold value, and a controller that uses the touch signal as a trigger input to control the low-pass filter and sample-and-hold circuit, and performs sampling of the sample-and-hold circuit when outputting the touch signal. At the same time, the cut-off frequency of the low-pass filter is switched to the high-frequency side, and after the touch signal is detected, the sample-and-hold circuit is controlled to cancel sampling and the cut-off frequency of the low-pass filter is returned to the low-frequency side. A touch signal detection circuit characterized in that a frequency drift component is removed and touch signal detection is performed based on the absolute value of a change at the time of contact.