JP5582986B2 - Proximity sensor - Google Patents

Description

  The present invention relates to a proximity sensor that detects the position of an object.

  Conventionally, it has so-called proximity that has two antennas, generates an alternating electromagnetic field from one antenna, receives it by the other antenna, and detects the phase of the received signal to detect the position and movement of the object. Sensors have been proposed (see, for example, Patent Documents 1 and 2).

  FIG. 36 is a circuit diagram showing a configuration of a conventional proximity sensor described in Patent Documents 1 and 2. In the conventional proximity sensor, the AC signal Ea is transmitted from the transmission antenna 103 based on the signal of the oscillator 102, and the AC signal Eb is taken into the circuit by the reception antenna 104. In the conventional proximity sensor, the signal taken into the circuit by the receiving antenna 104 is directly amplified by the amplifier 108 and then detected by the signal of the oscillator 102 by the phase detector 109.

  Furthermore, the conventional proximity sensor converts the output of the phase detector 109 into a direct current by the LPF 110 and outputs the change in the electromagnetic wave in the inspection region from the output terminal 111 as the change in the direct current voltage.

JP 2006-275629 A (page 3-5, FIG. 1) JP 2007-171031 A (page 4-6, FIG. 1)

  However, the prior art has the following problems. Since the phenomenon described above is very weak, a sufficient gain cannot be obtained unless the frequency is high due to the characteristics of the antenna or the interaction between the object to be detected and the radio wave. Therefore, in order to obtain sufficient detection sensitivity as a proximity sensor, it is necessary to generate a signal with a very high frequency from the oscillator 102 in both methods of Patent Documents 1 and 2. In Patent Document 1 conscious of low frequencies, a high frequency of the lowest HF band is assumed, and in Patent Document 2, a GHz band is assumed.

  On the other hand, in order to generate a high-frequency signal, a large amount of energy must be input, and there is a problem that a circuit configuration with a large power consumption for dealing with the high-frequency signal must be used for the entire circuit.

  In the configuration in which the input to the amplifier 108 is not connected to anything other than the antenna 4 as shown in FIG. 36, the potential of the AC signal Eb is not determined, and the output of the amplifier 108 does not fall within the power supply voltage range. Eb has a problem of sticking to either a positive or negative power supply voltage.

  In order to avoid this, as shown in FIG. 37, the AC signal Eb from the receiving antenna 4 may be clamped to the intermediate potential of the amplifier using a large resistor 7T. In this way, the AC signal Eb from the receiving antenna 4 can be measured.

  In order to avoid the attenuation of the AC signal Eb due to the resistance connection, as shown in FIG. 38, assuming that the electrical connection only needs to pass the DC, the inductor 7LT is connected in series between the resistor 7T and the intermediate potential. Good. This can prevent the AC signal from being attenuated.

  However, in the configuration shown in FIGS. 37 to 38, there is almost no change in the phase when radio waves are transmitted and received. Therefore, in this method, as shown in FIG. 39, phase detection is performed with the received waveform of the AC signal Eb from the receiving antenna 4. Only the change in the amplitude of the received waveform that reflects the change in the object O is seen, as indicated by the arrows in the figure, with substantially the same detection phase. Therefore, the amplitude of the received waveform must be adjusted within the range of the power supply voltage by adjusting the amplification factor of the resistor 7LT or the resistor 7LT and the inductor 7LT and the amplifier 8. If the amplification factor is too low, the waveform will stick to the GND level and will not rise for a while, and if it is too high, the waveform will stick to the power supply voltage, making it impossible to observe changes in amplitude. What is important here is that there is a dead zone above and below the gain set by the resistor 7T or the inductor 7LT, and sensitivity cannot be obtained in this dead zone region. Although this operation must be performed precisely, the condition for determining the amplitude of the received waveform is easily influenced by changes in the external environment surrounding the receiving antenna 4, and as a result, the detection result has a poor SN and a large drift. .

  Further, as a more troublesome problem, the waveform of the received waveform, which is the detected signal, is asymmetrically attached to either positive or negative voltage level due to the effect of static electricity superimposed when the object O is charged. is there. This phenomenon drifts the detection result, but this drift is nothing but an error in the measurement result of the distance to the test object, and gives a fatal restriction that the test object O should not be charged.

  Accordingly, an object of the present invention is to provide a proximity sensor that solves the above-described problems, stabilizes sensitivity, and avoids an error in a measurement value due to disturbance due to static electricity or the like.

  In order to solve the above-described problems and achieve the object, the proximity sensor of the present invention adopts the following configuration.

  The proximity sensor of the present invention includes an AC signal generation source, a transmission antenna that transmits a radio wave based on a signal from the AC signal generation source, a reception antenna that receives the radio wave, and a phase shift signal from the AC signal generation source. 1 phase shift means, a synthesis means for synthesizing the signal phase-shifted by the first phase shift means and the signal received by the receiving antenna, and the synthesized signal synthesized by the synthesis means And a phase detection means for detecting the phase.

  Furthermore, the proximity sensor of the present invention is characterized in that, in addition to the configuration described above, a resistor or an inductor for connecting the transmitting antenna and the combining unit is provided as the first phase shifting unit.

  Further, the proximity sensor of the present invention has a second phase shift that shifts the signal from the AC signal generation source in accordance with the amount of phase shift by the first phase shift means and the receiving antenna in addition to the configuration described above. The phase detector includes a phase detector, and the phase detector detects the phase of the combined signal combined by the combiner using the signal phase-shifted by the second phase shifter.

Furthermore, in the proximity sensor of the present invention, in addition to the configuration described above, the phase detection means performs phase detection on the binarized composite signal using the binarized AC signal generation source signal. And

  Furthermore, the proximity sensor of the present invention is characterized in that, in addition to the configuration described above, a resistor for connecting the receiving antenna and the reference potential is provided.

  Furthermore, the proximity sensor of the present invention includes a resistor and an inductor for connecting the receiving antenna and the reference potential in addition to the above-described configuration.

  Furthermore, the proximity sensor of the present invention has a first amplifier that amplifies the signal received by the receiving antenna and a second signal that amplifies the signal phase-shifted by the first phase-shifting means, in addition to the configuration described above. And an adder for adding the signals amplified by the first amplifier and the second amplifier as a synthesizing means.

  Furthermore, the proximity sensor of the present invention includes, in addition to the above-described configuration, a boosting unit that boosts the power supply of the circuit of the AC signal generation source between the AC signal generation source and the transmission antenna, and an AC signal generation source. And amplifying means for amplifying the signal by a power supply system boosted by the boosting means.

  Furthermore, the proximity sensor of the present invention is characterized by including a frequency divider between the AC signal generation source and the transmission antenna in addition to the above-described configuration.

  Furthermore, the proximity sensor of the present invention is characterized by comprising shielding means for shielding radio waves emitted from the AC signal generation source in addition to the configuration described above.

  Furthermore, the proximity sensor of the present invention is characterized in that, in addition to the configuration described above, a logarithmic amplifier circuit is provided at the subsequent stage of the phase shift detection means.

  The proximity sensor of the present invention combines a signal obtained by shifting the phase of the signal from the AC signal generation source and the signal received by the receiving antenna, and detects the phase of the combined signal using the signal from the AC signal generation source. As a result, a change in the signal received by the receiving antenna can be detected as a change in the phase of the combined signal of the signal obtained by shifting the signal from the AC signal source and the signal received by the receiving antenna. Compared with the prior art in which phase detection is performed using the signal as it is, the sensitivity can be stabilized and an error in the measured value due to disturbance due to static electricity or the like can be avoided.

It is a circuit diagram which shows the structure of the proximity sensor of Example 1 of this invention. It is a wave form diagram explaining operation | movement of the proximity sensor of Example 1 of this invention. It is a wave form diagram explaining operation | movement of the proximity sensor of Example 1 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 1 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 1 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 2 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 3 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 4 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 5 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 6 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 7 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 8 of this invention. It is a circuit diagram of the logarithmic amplifier circuit of the proximity sensor of Example 9 of the present invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 10 and Example 11 of this invention. It is a wave form diagram explaining operation | movement of the proximity sensor of Example 11 of this invention. It is a wave form diagram explaining operation | movement of the proximity sensor of Example 11 of this invention. It is a wave form diagram explaining operation | movement of the proximity sensor of Example 11 of this invention. It is a circuit diagram which shows the structure of the proximity sensor of Example 12 of this invention. It is a wave form diagram explaining operation | movement of the proximity sensor of Example 12 of this invention. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the relationship between the test object approached to the antenna, and the output voltage of the said sensor. It is explanatory drawing which shows the structural example of the transmission antenna and reception antenna which were formed on the transparent substrate. It is explanatory drawing which shows the structural example of the transmission antenna and reception antenna which were formed on the transparent substrate. It is explanatory drawing which shows the structural example of the transmission antenna and reception antenna which were formed on the transparent substrate. It is explanatory drawing which shows the structural example of the transmission antenna and reception antenna which were formed on the transparent substrate. It is explanatory drawing which shows the structural example of the transmission antenna and reception antenna which were formed on the transparent substrate. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is explanatory drawing which shows the structural example of a transmitting antenna and a receiving antenna. It is a circuit diagram which shows the structure of the conventional proximity sensor. It is a circuit diagram which shows the structure of the conventional proximity sensor. It is a circuit diagram which shows the structure of the conventional proximity sensor. It is a wave form diagram explaining operation | movement of the conventional proximity sensor.

Hereinafter, embodiments of the present invention will be described in detail.
Example 1: FIGS. 1 to 5
First, the configuration of the proximity sensor according to the first embodiment of the present invention will be described. FIG. 1 is a circuit diagram illustrating a configuration of the proximity sensor 1a according to the first embodiment. As shown in FIG. 1, the proximity sensor 1 a includes an oscillator 2 and a transmission antenna 3 that radiates an AC signal Ea to a region to be inspected based on a low-frequency signal generated by the oscillator 2.

  The oscillator 2 is an example of an AC signal generation source, and is configured using, for example, a crystal resonator. The AC signal Ea radiated from the transmitting antenna 3 has high frequency stability because the stability of the frequency and intensity affects the output stability of the proximity sensor, and is stable with respect to temperature, changes with time, etc. It is desirable to use a simple crystal resonator.

  For example, a tuning fork type crystal resonator that enables oscillation in the VLF band is used in order to aim for a low power consumption configuration assuming that it is used in a portable device or the like. The circuit configuration of the oscillator may be a general Colpitts type generator circuit used for a timepiece or the like in consideration of low power consumption.

  In addition to quartz resonators, piezoelectric elements such as PZT thin films and ceramics (ceramic oscillators), MEMS vibrators formed on the surface of a vibrating body composed of piezoelectric elements such as PZT thin films, and tantalum The oscillator 2 may be configured using a vibrator using lithium acid single crystal, lithium niobate single crystal, or langasite.

  Further, the proximity sensor 1a includes a receiving antenna 4 that receives an AC signal Eb from the region to be inspected, and a resistor 7 that electrically connects the transmitting antenna 3 and the receiving antenna 4.

  The buffer 6 is provided in order to prevent the oscillator 2 from being affected by the circuit at the subsequent stage and causing a change in frequency and amplitude. The resistor 7 is a coupling resistance between the transmitting antenna 3 and the receiving antenna 4. If the value of the resistor 7 is too small, the electrical coupling becomes too strong. On the other hand, if the value of the resistor 7 is too large, the electrical coupling is too weak. . For this reason, selection of the resistance value of the resistor 7 is important. In the case of the first embodiment, the resistance value of the resistor 9 is suitably about 0.5 to 1 MΩ.

  Further, the proximity sensor 1 a includes an amplifier 8 that amplifies the output of the receiving antenna 4 and a phase detector 9 that detects the phase of the signal received by the receiving antenna 4 using the output signal of the oscillator 2. Further, the proximity sensor 1 a includes an LPF (low-pass filter) 10 that smoothes the output of the phase detector 9 and an output terminal 11.

  Next, the operation of the proximity sensor 1a having the above-described configuration will be described. In the following description, in order to clarify the operation, the reference signal from the amplifier 8 that is multiplied by the phase detector 9 changes the upper and lower power supply voltages alternately in advance using a binarization circuit, and only the phase information is obtained. The one processed into a rectangular wave with. The effects of other signals are the same regardless of whether they are a rectangular wave or a sine wave, but in this description, all signals are sine waves. Here, in order to actually change the waveform of the oscillation circuit to a sine wave, an AGC is required for the oscillation circuit.

  First, in FIG. 1, a low frequency signal is generated by an oscillator 2, and an AC signal Ea is radiated to a region to be inspected by a transmission antenna 3. The AC signal Ea radiated from the transmitting antenna 3 forms an electromagnetic field determined by the atmosphere, dielectric, conductor, etc. existing in this area in the area to be inspected. The receiving antenna 4 receives an AC signal Eb corresponding to an electromagnetic field formed in the inspection area.

  At this time, if an object existing in the inspected area does not move at all, the electromagnetic field formed by the AC signal Ea transmitted by the transmitting antenna 3 is in a steady state, and the AC signal Eb received by the receiving antenna 4 has a stable phase. And with amplitude. However, when an inspected object O having an appropriate dielectric constant such as a human finger enters this region, the electromagnetic field changes due to disturbance. As a result, the phase and mainly the amplitude of the AC signal Eb received by the receiving antenna 4 changes. The change in phase is very small and mainly changes in amplitude.

  FIG. 2 is a waveform diagram for explaining the operation of the proximity sensor according to the first embodiment of the present invention. In the first embodiment, as shown in FIG. 1, the input of the amplifier 8 is connected to the output of the buffer 6 which is the output of the oscillation circuit using a large resistor 7. Since the output from the buffer 6 has inherited the property of alternating current centered on the intermediate potential of the power supply voltage from the oscillator 2, the average value of alternating current can be clamped to the intermediate potential of the power supply voltage by this connection.

Also, with this configuration, a low-pass filter is formed between the output of the buffer 6 and the input of the amplifier 8 by the large value resistor 7 and the small parasitic capacitance 5 of the actual circuit element. The low-pass filter composed of the resistor 7 and the parasitic capacitance 5 serves as a first phase shift means to generate a signal waveform phase difference between the output of the buffer 6 and the input of the amplifier 8. The signal phase-shifted by the first phase-shifting means is shown by the phase-shifting transmission waveform of FIG.

  On the other hand, the AC signal Eb from the receiving antenna 4 does not cause a phase difference with the AC signal Ea from the transmitting antenna 3. A signal received by the receiving antenna 4 is shown by a received waveform in FIG. Further, the resistor 7 and the receiving antenna 4 are connected, and by this connection, the AC signal Eb from the receiving antenna 4 and the output signal from the resistor 7 are combined. The connection between the resistor 7 and the receiving antenna 4 is an example of a combining unit. The waveform of this synthesized signal is shown by the synthesized waveform in FIG.

  FIG. 3 is an explanatory diagram of changes in the composite waveform. As shown in FIG. 3, the amplitude and phase of this composite waveform change due to the change in amplitude of the received waveform that reflects the change in the object O. That is, a change in the amplitude of the received waveform that reflects the change in the object O is detected as a change in the amplitude and phase of the synthesized waveform by detecting the synthesized waveform at a detection position in phase with the received waveform.

  If the phase shift transmission waveform generated by the resistor 7 and the parasitic capacitance 5 is adjusted so that the amplitude exceeds the power supply voltage by adjusting the value of the resistor 7 or the amplification factor of the amplifier 8, the phase shift transmission waveform and The amplitude of the synthesized waveform is limited by the power supply voltage to become a trapezoidal waveform or a rectangular waveform, and a change due to the received waveform is reflected only in the phase of the synthesized waveform. In such a state, fine amplitude adjustment of each waveform is not necessary, and environmental factors that change the amplitude are excluded, and as a result, the SN of the detection result is improved.

  Further, by adjusting each signal so that the amplitude of the received waveform is smaller than that of the phase-shifted transmission waveform, the signal to be detected is affected by the effect of static electricity superimposed when the object O is charged. Can be suppressed as much as possible to a positive or negative voltage level as much as possible, and a robust proximity sensor that is not affected by the charging of the object O can be realized. Each signal is adjusted so as to reduce the amplitude of the received waveform as compared with the phase-shifted transmission waveform by adjusting the values of the resistor 7 and the parasitic capacitance 5. When the resistance 7 is increased, the ratio of the signal from the receiving antenna 4 is increased. Further, when the value of the parasitic capacitance 5 is increased, the ratio of the signal from the receiving antenna 4 is also increased. The overall level adjustment is performed by the amplifier 8.

  Such a configuration uses the inductor 7L instead of the resistor 7 as in the proximity sensor 1b shown in FIG. 4, or the resistors 7 and 7M instead of the resistor 7 as in the proximity sensor 1c shown in FIG. It can also be realized by using a series connection. In these configurations, the parasitic capacitance 5 shown by the broken line in FIGS. 1, 4 and 5 is actually a capacitor having a slightly larger value than the assumed parasitic capacitance in order to stabilize the capacitance value. You may add it.

  As described above, when an object to be inspected O having an appropriate dielectric constant such as a human finger enters the area to be inspected, the electromagnetic field changes due to disturbance. As a result, the phase and amplitude of the AC signal Eb received by the receiving antenna 4 change, so that the output of the phase detector 9 changes, and the DC output from the smoother 10 that smoothes this changes. The presence and movement of the test object O can be known by the change in the DC output.

  It should be noted here that the electromagnetic field in the region to be inspected formed by the transmission antenna 3 varies depending on the arrangement of objects in the region to be inspected, and the region to be inspected as viewed from the transmitting antenna 3 and the receiving antenna 4 is If it is interpreted as a range in which electromagnetic waves are formed, in principle, it extends to infinity. Therefore, an area that can be sensed by the proximity sensor according to the present embodiment without being buried in noise is defined as an inspected area, and an output in an environment in which the transmitting antenna 3 and the receiving antenna 4 are installed is set as a background. It is necessary to grasp the change due to the disturbance of this as a change from this background output.

[Example 2: FIG. 6]
Next, the configuration of the proximity sensor according to the second embodiment of the present invention will be described. FIG. 6 is a circuit diagram illustrating a configuration of the proximity sensor 2c according to the second embodiment. As shown in FIG. 6, the proximity sensor 2c according to the second embodiment includes a resistor 7T and an inductor 7LT that connect the reference potential and the receiving antenna 4 in addition to the proximity sensor 1a according to the first embodiment shown in FIG.

  A signal obtained by enhancing the output of the oscillation circuit 2 by the buffer 6 is radiated into the air by the transmitting antenna 3 and received by the receiving antenna 4. In the proximity sensor 2c shown in FIG. 6, this received waveform is generated by the resistor 7T and the inductor 7LT. The reference voltage level is adjusted. Similar to the proximity sensor 1 a of the first embodiment described with reference to FIG. 1, this reception waveform is superimposed on the phase transmission waveform from the buffer 6 phase-shifted by the resistance connected to the buffer 6 and the parasitic capacitance 5 and then applied to the amplifier 8. input.

This combined waveform is phase-detected with the reference signal from the buffer 6 by the phase detector 9, and the output from the output terminal 11 as a result of smoothing this signal with the LPF 10 is the combined waveform from the information from the receiving antenna 4. Observed as a phase change. With such a configuration, the effect of removing the influence of the SN improvement and the charging of the test object shown in the first embodiment is exhibited. FIG. 6 shows an example in which the resistor and the inductor for connecting the receiving antenna and the reference potential are provided for level adjustment of the receiving waveform. However, the receiving antenna and the reference potential may be connected only to the resistor or only to the inductor. good.

[Example 3: FIG. 7]
Next, the configuration of the proximity sensor according to the third embodiment of the present invention will be described. FIG. 7 is a circuit diagram illustrating a configuration of the proximity sensor 3a according to the third embodiment. In the circuit configurations shown in FIGS. 1 and 4 to 6, the values of the resistor 7 and the capacitor 8 are limited in the synthesis of each waveform.

  In the proximity sensor 3a shown in FIG. 7, the input signal from the receiving antenna 4 is grounded to the reference potential by the resistor 7U and the level is adjusted, and the signal from the oscillation circuit 2 is a low pass filter using the resistor 7T and the capacitor 5S. The phase-shifted signals are amplified to arbitrary voltages by the amplifier 6S1 (first amplifier) and the amplifier 6S2 (second amplifier), respectively, and then synthesized by the adder circuit 12. Here, the low-pass filter using the resistor 7S and the capacitor 5S is an example of the first phase shifting means, and the adder 12 is an example of the synthesizing means.

  The combined signal obtained by the adder 12 is phase-detected with the signal from the oscillation circuit 2 using the detector 9. By adopting such a configuration, the proximity sensor 3a shown in FIG. 7 can have a degree of freedom in the amplitude at the time of synthesis of each signal.

[Example 4: FIG. 8]
Next, a proximity sensor according to Example 4 of the present invention will be described. FIG. 8 is a circuit diagram illustrating a configuration of the proximity sensor 1d according to the fourth embodiment. As illustrated in FIG. 8, the proximity sensor 1 d according to the fourth embodiment includes a booster circuit 30 that boosts the power supply of the circuit of the oscillator 2 between the oscillator 2 and the transmission antenna 3 in the configuration of the proximity sensor 1 a according to the first embodiment. And an amplifier circuit 31 that amplifies the signal of the AC signal generation source by the power supply system boosted by the booster circuit 30. The booster circuit 30 is an example of a booster, and the amplifier circuit 31 is an example of an amplifier.

  With such a configuration, the signal output from the oscillator 2 is voltage amplified by the booster circuit 30 and the amplifier circuit 31, and the transmission antenna 3 is based on the signal amplified in comparison with the power supply voltage used by this apparatus. As a result, a stronger electromagnetic wave AC signal Ea is radiated to the inspection area.

Therefore, the proximity sensor 1d according to the fourth embodiment has a wider test area than the proximity sensor 1a according to the first embodiment even when the power supply voltage used is a low power supply voltage such as 3 V and 5 V, for example. O distance can be detected.

[Example 5: FIG. 9]
Next, the configuration of the proximity sensor according to the fifth embodiment of the present invention will be described. FIG. 9 is a circuit diagram illustrating a configuration of the proximity sensor 1X according to the fifth embodiment. As shown in FIG. 9, the proximity sensor 1 </ b> X according to the fifth embodiment implements a plurality of proximity sensors using one oscillator 2 and a transmission antenna 3, a plurality of reception antennas 4, and a phase shift detector 9. is there.

  When the proximity sensor 1X shown in FIG. 9 receives radio waves transmitted by sharing one oscillation circuit 2 and one transmission antenna 3 by the reception antennas 4R, 4L, 4U, and 4D, respectively, the amplifiers 8R and 8L are respectively received. , 8U, and 8D are input with signals reflecting different information depending on each receiving antenna. Even if the output signal of each amplifier is phase-detected with the reference signal from the buffer 6 that is the signal of the same oscillator 2, the output terminals 11R, 11L, 11U, and 11D smoothed by the LPFs 10R, 10L, 10U, and 10D are used. Produces separate outputs, which each reflect the signal from the receiving antennas 4R, 4L, 4U, 4D and can implement four proximity sensors.

  Further, the proximity sensor 1X shown in FIG. 9 includes resistors 7R, 7L, 7U, and 7D that connect the transmitting antenna 3 and the receiving antennas 4R, 4L, 4U, and 4D as the first phase shifting means. Here, it is feared that all the antennas are coupled by the resistors and the mutual inputs are affected. However, since the transmitting antenna 3 is kept in a stable state by the output of the buffer 6, signals from the respective receiving antennas are used. Is attenuated by resistance until it reaches the other antenna, interference between the receiving antennas does not occur, and four proximity sensors can be realized. Further, if phase shift is performed using a single first phase shift means and this signal is distributed to each receiving antenna using a buffer or the like, these interferences can be avoided without using a plurality of transfer means. The configuration can be realized.

[Example 6: FIG. 10]
Next, the configuration of the proximity sensor according to the sixth embodiment of the present invention will be described. FIG. 10 is a circuit diagram illustrating a configuration of the proximity sensor 1Y according to the sixth embodiment. As illustrated in FIG. 10, the proximity sensor 1 </ b> Y according to the sixth embodiment includes a plurality of proximity sensors using a plurality of oscillators 2 and transmission antennas 3 having different frequencies, a single reception antenna 4, and a plurality of phase shift detectors 9. Is realized.

  The proximity sensor 1Y shown in FIG. 10 shares a reception antenna 4 with radio waves transmitted using a plurality of oscillation circuits 2R, 2L, 2U, and 2D having different frequencies and a plurality of transmission antennas 3R, 3L, 3U, and 3D. When received, signals reflecting different information from the respective antennas are input to the respective amplifiers 8R, 8L, 8U, and 8D.

  Although the signals are input from the same receiving antenna 4 and mixed, the output signals of the amplifiers are the frequencies from the buffers 6R, 6L, 6U and 6D which are signals of a plurality of oscillation circuits 2R, 2L, 2U and 2D having different frequencies. Phase detection with reference signals having different phases from each other, separate outputs are obtained from the output terminals 11R, 11L, 11U, and 11D smoothed by the LPFs 10R, 10L, 10U, and 10D. The signals from 4L, 4U and 4D are reflected, and four proximity sensors can be realized.

Further, in the proximity sensor 1Y shown in FIG. 10, the output antennas 3R, 3L, 3U, and 3D and the receiving antenna 4 are connected by resistors 7R, 7L, 7U, and 7D. Here, it is feared that all the antennas are coupled due to the connection by resistors and the mutual input is affected. However, the output antenna is kept stable by the outputs of the buffers 6R, 6L, 6U, and 6D. Since the frequency and phase are different, interference between the transmitting antennas does not occur, and in this case as well, four proximity sensors can be realized.

  In general, it is described that the phase detector can be regarded as a very sharp band-pass filter, and can actually exclusively detect AC signals of different frequencies. However, interference is still generated when the frequency difference is small. The frequency difference used for each oscillator including the resonance phenomenon when the frequencies of the plurality of oscillators are close needs to be separated by about 100 Hz or more even when the VLF band is used. Furthermore, when using a high frequency, when using a plurality of proximity sensors, it is preferable to have a frequency difference of about 1% or more of the frequency to be used.

  Further, the proximity sensor 1Y shown in FIG. 10 includes an oscillator 2, a transmission antenna 3, and a plurality of phase shift detectors 9 having different frequencies, and a determination for determining a correct output from the output of each phase detector 9 by majority processing. Means may be further provided. With this configuration, even when a noise radio wave source having a frequency close to that of the oscillator 2 is present around the proximity sensor, the influence of the noise radio wave can be eliminated.

  In FIG. 9 and FIG. 10, the example provided with the resistance which connects the transmission antenna 3 and the receiving antenna 4 was shown as a 1st phase shift means. However, the present invention is not limited to this, and in the proximity sensor shown in FIGS. 9 and 10, as shown in FIGS. 4 and 5, an inductor or an inductor and a resistor are used as the first phase shift means. You may prepare a combination.

  Further, the proximity sensor shown in FIGS. 9 and 10 may include a resistor and an inductor for connecting the receiving antenna 4 and the reference potential, as shown in FIG. 6 (Example 2). Further, in the proximity sensor shown in FIG. 9 and FIG. 10, as shown in FIG. 7 (Example 3), the phase is shifted by the first amplifier that amplifies the signal received by the receiving antenna and the first phase shift means. A second amplifier that amplifies the received signal, and an adder that adds the signals amplified by the first amplifier and the second amplifier. Further, in the proximity sensor shown in FIGS. 9 and 10, as shown in FIG. 8 (Embodiment 4), the boosting means for boosting the power supply of the circuit of the AC signal generation source between the AC signal generation source and the transmission antenna. And amplifying means for amplifying the signal of the AC signal generation source by the power supply system boosted by the boosting means.

[Example 7: FIG. 11]
Next, the configuration of the proximity sensor according to the seventh embodiment of the present invention will be described. FIG. 11 is a circuit diagram illustrating a configuration of the proximity sensor 1Z according to the seventh embodiment. As described above, in general, the phase detector can be regarded as a very sharp band-pass filter and can exclusively detect AC signals having different frequencies. However, interference occurs when the frequency difference is small. The frequency difference used for each oscillator including the resonance phenomenon when the frequencies of a plurality of oscillators are close needs to be separated by about 100 Hz or more even when using the VLF band. If a radio wave transmission source having a frequency close to that of the oscillator to be used is present in the vicinity of the sensor, the proximity sensor will malfunction. The proximity sensor 1Z according to the seventh embodiment is configured to solve this problem.

  In the proximity sensor 1Z of the seventh embodiment, the oscillator 2 is assumed to have an oscillation frequency that is one digit higher than the frequency band used for phase detection. For example, a Colpitts oscillation circuit using an AT-cut crystal resonator having an oscillation frequency of several MHz may be used. For example, the output through the buffer 6 constituted by an inverter or the like is a rectangular wave, which is input to the frequency divider 13A, emitted from the transmitting antenna 3 as a frequency of about several tens of KHz, and received by the receiving antenna 4. The phase detector 9 detects a signal obtained by dividing the signal by the frequency divider 13A as a reference signal.

In the proximity sensor 1Z according to the seventh embodiment, the frequency of the radio wave existing in the external environment can be separated from the frequency used by the proximity sensor 1Z by allowing the frequency dividing ratio of the frequency divider 13A to be set arbitrarily. Thus, a function for avoiding the influence of the external radio wave environment is provided.

  In addition, when power consumption becomes a problem, a reference pulse is generated using a low-frequency oscillator, and an arbitrary frequency is generated by a so-called PLL in which the frequency generated by the RC oscillator is adjusted to an integral multiple of the reference pulse. Also good. In any case, a shield (blocking means) for blocking radio waves generated from the oscillating portion of the oscillator 2, such as surrounding the oscillator and the frequency divider with a grounded conductor, is provided, and this frequency is not affected by external radio waves. Can take structure. As a result, the influence of the original oscillation of the oscillator 2 due to the radio wave can be suppressed.

[Example 8: FIG. 12]
Next, the configuration of the proximity sensor according to the eighth embodiment of the present invention will be described. FIG. 12 is a circuit diagram illustrating a configuration of the proximity sensor 1U according to the eighth embodiment. The proximity sensor 1U according to the eighth embodiment uses a plurality of proximity sensors and antennas and has a function of avoiding the influence of the radio wave environment. When a proximity sensor is incorporated in an automatic machine, it is necessary to automatically save a frequency so as not to be affected by external radio waves as described in the seventh embodiment.

  In the proximity sensor 1U of the eighth embodiment shown in FIG. 12, the frequency generated by the oscillation circuit 2 is divided into three division ratios by the frequency divider 13B, and a proximity sensor is configured for each frequency. Yes. In addition, the proximity sensor 1U shown in FIG. 12 may further include a determination unit that determines a correct output by majority processing from the outputs of the phase detectors 9X, 9Y, and 9Z. With this configuration, even when a noise radio wave source having a frequency close to that of the oscillator 2 is present around the proximity sensor, the influence of the noise radio wave can be eliminated. Here, as described in the fifth embodiment, the transmission antennas 3X, 3Y, and 3Z of these three proximity sensors may be the same, and the reception antennas 4X, 4Y, and 4Z are the same. It doesn't matter.

[Example 9: FIG. 13]
Next, the configuration of the proximity sensor according to the ninth embodiment of the present invention will be described. FIG. 13 is a circuit diagram of a logarithmic amplifier circuit used in the proximity sensor of the ninth embodiment. The configuration of the above-described eighth embodiment is assumed to be incorporated in an automatic machine and improve its reliability. In such a case, the output 11 from the output terminal 11 is often used after being digitized by an AD converter. However, as shown in FIG. 22 described later, when the antenna is shaped like a dot and a ring and the sensitivity is dependent only on the distance between the antenna and the object to be examined, the sensitivity is inversely proportional to the distance.

  The output inversely proportional to the distance becomes very large at a point where the distance is small, that is, near the antenna. On the other hand, the output is small in the region where the distance from the antenna is large. Therefore, if the distance resolution in a region far from the antenna is ensured and the potential is uniformly AD converted, an AD converter having a very high resolution as a whole must be used.

  Since the high-resolution AD converter has a large circuit scale and is difficult to manufacture with high yield, in Example 9, the output of the proximity sensor is amplified using a logarithmic amplifier circuit as shown in FIG. use. As a result, the rate of change in the voltage in the vicinity of the antenna that generates a high voltage decreases, and as a result, a low-precision AD converter with low resolution can be used.

The operation of the logarithmic amplifier circuit shown in FIG. 13 will be described. FIG. 13 shows the connection of an operational amplifier 18, an input resistor 19 and a transistor 17 instead of a feedback resistor. The basic operation is inverting amplification by the operational amplifier 18, a resistor 19 is provided at the inverting input terminal of the operational amplifier, and an emitter and a collector of the transistor are provided between the output terminal and the inverting input terminal of the operational amplifier 18 in order to change the feedback rate. Is connected. A positive input terminal for providing a reference potential of the operational amplifier 18 is provided. In this circuit, the current I19 flowing through the resistor 19 is I19 = ∨19 / R19 due to a virtual short, assuming that the input voltage is ∨19. Since this current flows through the transistor 18 as a feedback current of the operational amplifier, the base-emitter voltage ∨BE of the transistor is generally a constant K, and ∨BE = KlogI19, that is, ∨BE = Klog (∨19 / R19). It becomes. Since the output voltage ∨O is a potential seen from the virtual short, ∨O = −Klog (∨19 / R19), and the logarithm of the input voltage ∨19 is output as VO.

[Example 10: FIG. 14]
Next, the configuration of the proximity sensor according to Example 10 of the present invention will be described. FIG. 14 is a circuit diagram illustrating a configuration of the proximity sensor 1V according to the tenth embodiment. As shown in FIG. 14, the proximity sensor 1V of the tenth embodiment uses the phase of the reference signal for phase detection used for the detector 9 by shifting the phase using a resistor 7B, a capacitor 5B, and an amplifier 8B.

  In the first embodiment shown in FIG. 1, the information from the receiving antenna 4 is phase-shifted from the oscillation waveform using the resistor 7 and the capacitor 5 and synthesized with the signal from the receiving antenna 4 to recover the phase shift change information of the synthesized waveform. However, the resistor 7 and the capacitor 5 used in the low-pass filter for this phase shift operation have temperature characteristics, and their electrical constants change. Since these constant temperature changes change the phase shift amount, the output of the sensor of the first embodiment has a temperature drift characteristic as a result, and the accuracy of the sensor is lowered. Example 10 describes a configuration for reducing this temperature drift, and describes a configuration for improving practical performance as a sensor.

  When there is no information from the receiving antenna 4 in the first embodiment, only a signal whose phase is shifted by using the resistor 7 and the capacitor 5 is sent to the detector 9. Therefore, the detection result of the phase-shifted oscillation waveform gives a point where the output of the sensor output is zero. The temperature drift which is a problem in this embodiment is the temperature drift of the sensor 0 point output. In the present configuration in which the oscillation waveform shifted in phase using the oscillation waveform is detected, most of the causes of the drift are Occurs in the process of phase shift. As described above, the specific factor is that, as described above, the resistor 7 and the capacitor 5 used in the low-pass filter for the phase shift operation have temperature characteristics, and their electric constants change.

  Therefore, in the tenth embodiment, the reference signal for detection is used after being phase-shifted. That is, the reference signal is phase-shifted by forming a low-pass filter using the resistor 7B and the capacitor 5B as the second phase shift means, and then the waveform is shaped through the amplifier 8B. Furthermore, in the receiving unit, when the antenna 4 is installed, a phase change occurs due to the capacitive component of the antenna 4 itself and the shield wire of the electrical connection unit to the antenna 4 installation location. It becomes complete by adding the same amount of capacity. That is, although not shown in the drawing, if the same coaxial cable used for the electrical connection from the connecting portion of the resistor 7 and the capacitor 5 to the antenna 4 is connected to the connecting portion of the resistor 7B and the capacitor 5B. Good. Further, if a dummy antenna having a capacity equivalent to that of the antenna 4 is connected to the tip, the completeness of correction is further improved.

When the capacity of the antenna unit is small, elements used for the resistor 7B and the capacitor 5B used for the amplifier phase shift are substantially the same as those used for the resistor 7 and the capacitor 5. When the capacity of the antenna part is large, the antenna 4B (not shown) having the same capacity as the antenna 4 and shielded from the outside is connected to the junction between the resistor 7B and the capacitor 5B, or the capacity of the capacitor 5B is adjusted, The amount of phase shift of the detector may be matched with the amount of phase by the antenna 4. By using such a configuration, the phase-shifted oscillation waveform combined with the received waveform and the phase-shifted oscillation waveform used for detection are substantially the same signal, and the temperature change that occurs in each signal due to the temperature characteristics of each circuit element Are substantially the same, and the result detected by the detector 9 is not affected by the temperature change of each element, and as a result, in the tenth embodiment, a sensor with little temperature drift can be realized.

[Example 11: FIGS. 14 to 17]
Next, the configuration of the proximity sensor according to Example 11 of the present invention will be described. The proximity sensor according to the eleventh embodiment is the same as the proximity sensor according to the tenth embodiment shown in FIG. In this embodiment, it is used as a comparator.

  If a rectangular wave is generated and used by a comparator, the oscillator 2 does not need to be added with an AGC circuit to make a sine wave in advance, and the power is limited by the power source used, so that the pseudo ratiometric is automatically set. When the output of this sensor is digitized using an AD converter, the influence of the power supply voltage fluctuation can be canceled by sharing the power supply.

  Also, if the oscillation waveform is a rectangular wave, the frequency is high, but it is possible to use an oscillator using, for example, a quartz AT-cut resonator that is inexpensive and excellent in frequency temperature characteristics, and uses a digital circuit such as an FF. If the frequency is divided by the above, various frequencies can be used by one oscillator.

  By making the oscillation waveform a rectangular wave, the amplitude information of the waveform is lost and there is no need to consider it as a temperature characteristic. Therefore, the influence of temperature is reflected only in the phase information. As compared with the case of Example 10, the temperature characteristics can be further improved.

  The operation when all signals below the oscillation waveform are rectangular waves will be described in detail below. As shown in FIG. 15, when the oscillation waveform generated by the oscillator by the comparator 6 becomes a rectangular wave limited by the voltage level, the phase-shifted oscillation waveform becomes a sawtooth waveform at the exit of the low-pass filter. When the amplifier 8 amplifies again to a sufficient amplitude, the phase-shifted oscillation waveform becomes a rectangular wave obtained by shifting the oscillation waveform indicating the detection position by several tens of degrees. Further, when the received waveform is not 0 and is amplified to a sufficient amplitude by the amplifier 8 after being combined with the phase-shifted oscillation waveform, the combined waveform becomes a rectangular wave in which the phase-shifted oscillation waveform is further phase-shifted due to the influence of the received waveform.

  Next, the actual state of detection will be described with reference to FIG. FIG. 16 shows the waveform of a rectangular wave over six stages. The lower end of the rectangular wave represents the 0 level indicating the GND potential, and the upper end represents the 1 level indicating the power supply voltage. First, an oscillation waveform indicating a detection position is shown in the uppermost stage. In the second stage, a phase-shifted oscillation waveform is shown. The phase-shifted oscillation waveform is shown as an oscillation waveform or a waveform whose phase is shifted by, for example, several tens of degrees in the right direction, that is, delayed. The third stage shows a composite waveform obtained by synthesizing the received waveform with the phase-shifted oscillation waveform. Here, the phase is shifted to the left by several degrees and the phase is advanced by the received waveform.

  The fourth stage shows the result of detecting the second-stage phase-shifted oscillation waveform using the oscillation waveform indicating the first-stage detection position. The detection is the same as the logical product operation of the phase-shifted oscillation waveform by the oscillation waveform, and the state in which the one-level section is reduced is shown. The zero point of the sensor is indicated by a voltage level in which this signal is passed through the LPF and converted into a direct current. The fifth stage shows the result of detection of the third-stage composite waveform using the oscillation waveform indicating the first-stage detection position. The detection is the same as the logical product operation of the synthesized waveform by the oscillation waveform, and the voltage level that makes this signal DC through the LPF will increase compared to the case where there is no received waveform shown in the fourth stage. It is shown. The sixth stage shows the difference between the phase-shifted oscillation waveform after detection shown in the fourth stage and the synthesized waveform after detection. The influence of the received waveform can be grasped as a voltage level obtained by smoothing the waveform at the sixth stage with the LPF.

  The phase shift of the phase shift oscillation waveform described here is performed by the resistor 7 and the capacitor 5 described above, and the amount of phase shift is as large as several tens of degrees. Realization of a large phase shift means that the influence of the temperature change of the circuit element is large.

  Next, the case where the phase of the reference signal for detection is shifted will be described with reference to FIG. FIG. 17 shows the waveform of a rectangular wave over six stages as in FIG. The lower end of the rectangular wave represents the 0 level indicating the GND potential, and the upper end represents the 1 level indicating the power supply voltage. First, in the uppermost stage, a state in which the oscillation waveform for the detection position is phase-shifted by the resistor 7B and the capacitor 5B and binarized by the amplifier 8B is described. The phase shift oscillation waveform is shown in the second stage. The phase shift oscillation waveform is a phase shift of the oscillation waveform by the resistor 7 and the capacitor 5 and binarized by the amplifier 8. This is the phase shift oscillation waveform shown in the first stage. It is almost the same as the phase detection position. The third stage shows a composite waveform obtained by synthesizing the received waveform with the phase-shifted oscillation waveform. Here, the phase is shifted to the left by several degrees and the phase is advanced by the received waveform.

  The fourth stage shows the result of detecting the second-stage phase-shifted oscillation waveform using the oscillation waveform indicating the first-stage detection position. The detection is the same as the logical product operation of the phase-shift oscillation waveform by the oscillation waveform, and it is shown that both are substantially the same because both have undergone the same phase shift. The zero point of the sensor is indicated by a voltage level in which this signal is passed through the LPF and converted into a direct current. The fifth stage shows the result of detection of the third-stage composite waveform using the oscillation waveform indicating the first-stage detection position. The detection is the same as the logical product operation of the composite waveform by the oscillation waveform, and the voltage level that makes this signal DC by passing this signal through the LPF will be lower than when there is no reception waveform shown in the fourth stage. It is shown. The sixth stage shows the difference between the phase-shifted oscillation waveform after detection shown in the fourth stage and the synthesized waveform after detection. The influence of the received waveform can be grasped as a voltage level obtained by smoothing the waveform of the sixth stage with the LPF, but this amount is not changed by the phase shift of the waveform for detection.

  The phase shift of the phase shift oscillation waveform described here is performed by the resistor 7 and the capacitor 5 described above, and the amount of phase shift is as large as several tens of degrees. On the other hand, the phase shift of the phase-shift oscillation waveform for detection is performed by the resistor 7B and the capacitor 5B, and the amount of phase shift is as large as several tens of degrees. Realizing a large phase shift means that the influence of the temperature change of the circuit element is large, but by setting both phase shift amounts to the same, the influence of the phase shift due to the temperature change of the circuit element cancels each other out. The detection result is hardly affected. It should be noted that the influence of the received waveform on the phase of the detection waveform affects the direction of the voltage output of the detection result.

[Example 12: FIGS. 18 to 19]
Next, the configuration of the proximity sensor according to Example 12 of the present invention will be described. Also in this embodiment, the buffer 6 has a function of a comparator, and a rectangular wave signal is used for the subsequent signals. FIG. 18 is a circuit diagram illustrating a configuration of the proximity sensor 1W according to the twelfth embodiment. In this circuit, an exclusive OR element is used for phase detection without using a multiplication element. As shown in the description so far, the calculation in the digital circuit can be applied to the rectangular wave signal. In the phase detection, a multiplication element is normally assumed. In the eleventh embodiment, an AND element is used. The element used in FIG. 18 for explaining the present embodiment is different from the structure shown in FIG. 14 used for the explanation of the eleventh embodiment. This logical product element for phase detection is changed to an exclusive OR element 99. It has only been replaced.

  The operation of this embodiment will be described with reference to FIG. FIG. 19 shows the waveform of a rectangular wave over five stages, similar to FIG. The lower end of the rectangular wave represents the 0 level indicating the GND potential, and the upper end represents the 1 level indicating the power supply voltage. First, in the uppermost stage, a state in which the oscillation waveform for the detection position is phase-shifted by the resistor 7B and the capacitor 5B and binarized by the amplifier 8B is described. The phase shift oscillation waveform is shown in the second stage. The phase shift oscillation waveform is a phase shift of the oscillation waveform by the resistor 7 and the capacitor 5 and binarized by the amplifier 8. This is the phase shift oscillation waveform shown in the first stage. It is almost the same as the phase detection position. The third stage shows a composite waveform obtained by synthesizing the received waveform with the phase-shifted oscillation waveform. Here, the phase is shifted to the left by several degrees and the phase is advanced by the received waveform.

  The fourth stage shows the result of exclusive ORing the second-stage phase-shifted oscillation waveform with the oscillation waveform indicating the detection position of the first stage. In the exclusive OR operation, if there is no difference between the two signals, the output becomes 0, so that the output becomes all 0 by this operation. The fifth stage shows the result of exclusive OR of the synthesized waveform of the third stage with the oscillation waveform indicating the detection position of the first stage. Compared to the reference signal shown in the first stage, the synthesized waveform whose phase is changed by the received waveform due to exclusive OR is different from the reference signal shown in the first stage by the amount of this phase change. 1 signal is generated at all edges of the signal reflecting. The exclusive OR waveform reflecting the received waveform shown in the fifth stage is exactly twice as much as the logical product waveform reflecting the received waveform shown in the eleventh embodiment. This reflects that only one of the rising and falling information in the change of the rectangular wave signal can be grasped in the logical product, whereas both information can be grasped in the exclusive logical sum. In other words, the configuration of the eleventh embodiment is half-wave rectification, whereas the configuration of the present embodiment realizes full-wave rectification.

  As described above, in this embodiment, full-wave rectification capable of taking twice as much information is realized only by replacing rectangular wave detection by logical product with rectangular wave detection by exclusive OR.

[Configuration Examples of Transmitting Antenna and Receiving Antenna: FIGS. 20 to 35]
Next, the configuration of the transmission antenna 3 and the reception antenna 4 used in each embodiment of the proximity sensor described above will be described. 20 to 35 are explanatory diagrams of the configurations of the transmission antenna 3 and the reception antenna 4.

  In the proximity sensor of each embodiment described above, some arrangement is required for the arrangement of the transmission antenna 3 and the reception antenna 4. Considering the efficiency of the antenna, the planar transmission antenna 3a and the reception antenna 4a are arranged in parallel as shown in FIG. 20, or the rod-like transmission antenna 3b and the reception antenna 4b are arranged in parallel as shown in FIG. The arrangement for detecting the approach of the object to be measured in the space region between the antennas has the largest change in the way of propagation of electromagnetic waves, and the sensitivity as a sensor is large. Further, it is desirable to provide shields 15 and 16 in the wiring part in order to suppress the influence on the reception and transmission of signals in the wiring part.

However, in the antenna configurations shown in FIGS. 20 and 21, even if the distance between the test object and the antenna is the same, the output of the proximity sensor differs if the direction of movement of the test object with respect to the antenna is different. End up.
Hereinafter, with reference to FIGS. 22 to 25, the configuration of the transmitting antenna 3 and the receiving antenna 4 in which the output of the proximity sensor does not depend on the moving direction of the object to be detected with respect to the antenna but depends on the distance between the antenna and the object to be detected. explain.

  The antenna configuration shown in FIG. 22 includes a rod-shaped transmitting antenna 3c and a ring-shaped receiving antenna disposed at an equal distance from the rod-shaped transmitting antenna 3c in a plane perpendicular to the direction in which the rod-shaped transmitting antenna 3c extends. 4c. The rod-shaped transmitting antenna 3c is provided with a shield 15 at a portion excluding a minute portion at the tip, and the ring-shaped receiving antenna 4c is provided with a shield 16 at a portion excluding the ring portion.

In the antenna having the configuration shown in FIG. 22, the electromagnetic wave transmitted from the transmission antenna 3c is symmetric about the rod-shaped portion of the transmission antenna 3c. Further, in the antenna having the configuration shown in FIG. 22, when the ring diameter of the receiving antenna 4c is reduced, the electromagnetic field formed from the transmitting antenna 3c to the receiving antenna 4c is considered to be centrally symmetric from a position separated by a predetermined distance. Can do.
Therefore, the antenna configured as shown in FIG. 22 can be configured such that the output of the proximity sensor does not depend on the moving direction of the test object with respect to the antenna but depends on the distance between the antenna and the test object.

  The antenna having the configuration shown in FIG. 23 includes a receiving antenna 4d in which a plurality of concentric rings are joined to the antenna having the configuration shown in FIG. The antenna having the configuration shown in FIG. 24 includes a coil-shaped receiving antenna 4e wound a plurality of times in the antenna having the configuration shown in FIG. With the configuration shown in FIGS. 23 and 24, it is possible to improve the reception sensitivity of the antenna. The reception sensitivity of the antenna increases with the number of rings.

  The antenna having the configuration shown in FIG. 25 is provided with a transmission antenna 3d having a coiled tip portion wound a plurality of times in the antenna having the configuration shown in FIG. With this configuration, it is possible to increase the area functioning as a transmission antenna and improve the output of the transmission antenna. The transmission antenna 3d may be combined with the reception antennas 4c and 4d shown in FIGS.

FIG. 26 illustrates an experiment using the proximity sensor 1c according to the third embodiment including the antenna having the configuration illustrated in FIG. 25. As a result of the experiment, the test object close to the antenna and the output voltage of the sensor are measured. Show the relationship. A human finger is used as the test object. In FIG. 26, the horizontal axis (X axis) indicates the distance from the center of the antenna to the object to be detected, and the vertical axis (Y axis) indicates the output voltage of the sensor. The solid line in FIG. 26 indicates the output of the sensor, and the broken line indicates a line approximated by Y = 3000 / X-50.

  The output of the proximity sensor used in this experiment is a direct current. In FIG. 26, the output voltage is shown as a difference value from the output value when the test object is sufficiently away from the proximity sensor. The output of the proximity sensor used in this experiment has a noise of about 2 mVrms. As shown in FIG. 26, the output is buried in the noise at a distance exceeding 5 cm, and measurement becomes impossible.

  Further, as shown in FIG. 26, it can be confirmed that the output of the proximity sensor used in this experiment is almost inversely proportional to the distance from the center of the antenna of the test object. Thus, the fact that the output is inversely proportional to the distance of the object to be tested confirms that the distance detection operation by the proximity sensor is caused by electromagnetic waves rather than electrostatic fields.

  It was also confirmed that the proximity sensor used in this experiment was able to detect an object to be detected within a distance of about 5 cm with sufficient S / N when the output of the oscillator 2 was a voltage amplitude of 5V. If the output of the oscillator 2 is set to a voltage amplitude of 100 V with the proximity sensor of the present invention, a test object within a distance of about 1 m can be detected with sufficient S / N.

22 to 25 show an example in which the rod-shaped transmission antenna 3 and the ring-shaped reception antenna 4 are provided. However, the transmission antenna 3 may have a ring shape and the reception antenna 4 may have a rod shape.
The transmitting antenna 3 and the receiving antenna 4 described with reference to FIGS. 20 to 25 are antenna configurations optimized for sensitivity when the installation environment is not so limited.

  Recently, there is an increasing need for an input device linked to video information drawn on a display, that is, an input device called a touch panel. If the transmission antenna and the reception antenna of the proximity sensor of the present invention are arranged at different positions on the display, it is possible to configure a position detection device that detects the position of the test object located in the three-dimensional region on the display. The input device can be configured by controlling the input to the device in accordance with the three-dimensional position information of the object to be examined by this position detection device.

  Hereinafter, the transmitting antenna 3 and the receiving antenna 4 formed using a transparent electrode such as ITO on a transparent substrate in order to constitute such a position detection device will be described. FIG. 27 is a first configuration example of the transmitting antenna 3 and the receiving antenna 4 formed using a transparent electrode on a transparent substrate.

  The antenna configuration shown in FIG. 27 includes a transmitting antenna 3f and a receiving antenna 4f formed on a transparent substrate 25 such as glass or resin in a ring shape by transparent wiring using a transparent electrode such as ITO. The pattern of the receiving antenna 4f is formed concentrically around the pattern of the transmitting antenna 3f. By forming the transmitting antenna and the receiving antenna in a concentric ring shape in this way, the antenna and the test object are independent of the moving direction of the test object with respect to the antenna, similarly to the antenna configuration shown in FIGS. The output of the proximity sensor depending on the distance can be obtained.

In addition, it is necessary to perform wiring for connecting the transmitting antenna 3f and the receiving antenna 4f to a circuit unit (not shown) that constitutes the proximity sensor, but in order to suppress the influence on the reception and transmission of the signal of the wiring unit, It is desirable to provide shields 15 and 16.
In FIG. 27, an example in which the transmission antenna and the reception antenna are formed in one ring-shaped pattern is shown, but one or both of the transmission antenna and the reception antenna may be formed in a double or more ring-shaped pattern. good. The reception sensitivity of the antenna can be improved by increasing the number of rings of each antenna.

  Usually, the display area is rectangular. When an object located in the three-dimensional space on the rectangular area is detected by, for example, four proximity sensors, it is reasonable to arrange the antennas of the proximity sensors at the corners of the rectangular area.

  Here, as described above, since the output of the proximity sensor of the present invention is inversely proportional to the distance between the object to be measured and the center of the antenna, the output of the sensor becomes too large near the center of the ring of the antenna. Further, the vicinity of the center of the ring of the antenna is also a singular region where the situation where the sensitivity is inversely proportional to the distance is distorted. Therefore, the vicinity of the center of the ring is not suitable for detection.

However, when the antenna having the configuration shown in FIG. 27 is arranged at the corner of the rectangular region, the vicinity of the center of the ring of the antenna is located inside from the corner. Further, when the antenna is formed with a large ring in order to increase sensitivity, the vicinity of the center of the ring of the antenna is positioned further inside.
That is, even if the antenna having the configuration shown in FIG. 27 is arranged at the corner of the rectangular area, the vicinity of the center of the ring unsuitable for detection is located inside the corner of the rectangular area. There is a problem that an object located in space cannot be detected correctly.

  FIG. 28 is a configuration for solving such a problem, and is a second configuration example of the transmission antenna 3 and the reception antenna 4 formed using a transparent electrode on a transparent substrate. In the configuration of the antenna shown in FIG. 28, a 1/4 arc transmission antenna 3g1 and a reception antenna 4g1 are connected to the transparent substrate 25 by transparent wiring using a transparent electrode such as ITO at the corner of the transparent substrate 25. It is formed across two sides. The pattern of the receiving antenna 4g1 is formed in a concentric circular arc shape surrounding the pattern of the transmitting antenna 3g1.

  Wiring for connecting to the circuit unit (not shown) constituting the proximity sensor is performed from each of the transmission antenna 3g1 and the reception antenna 4g1 via the connection terminals 27 and 28. In order to suppress the influence on the reception and transmission of the signal of the wiring part, it is desirable to provide shields 15 and 16 in the wiring part.

Similarly, the transmitting antennas 3g2-3g4 and the receiving antennas 4g2-4g4 are formed in the other corners of the transparent substrate 25 in a 1/4 arc pattern. The pattern of the receiving antennas 4g2-4g4 is formed in a concentric circular arc shape surrounding the pattern of the transmitting antennas 3g2-3g4.
Here, the transmitting antenna 3g2 and the receiving antenna 4g2, the transmitting antenna 3g3 and the receiving antenna 4g3, and the transmitting antenna 3g4 and the receiving antenna 4g4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 28, only wiring from the transmitting antenna 3g1 and the receiving antenna 4g1 is shown.

  In the configuration example shown in FIG. 28, by forming the transmitting antenna and the receiving antenna in a quarter arc shape, the vicinity of the center of the ring that is not suitable for detection can be positioned at the corner of the rectangular region. This makes it possible to correctly detect an object located in the three-dimensional space on the display area.

  In the configuration example shown in FIG. 28, the transmitting antenna and the receiving antenna are formed in concentric circular arcs, so that the inner side of the rectangular area does not depend on the moving direction of the test object with respect to the antenna, The output of the proximity sensor depending on the distance of the test object can be obtained.

  FIG. 29 shows a third configuration example of the transmission antenna 3 and the reception antenna 4 formed using a transparent electrode on a transparent substrate. In the antenna configuration shown in FIG. 29, arc-shaped transmitting antennas 3h1-3h4 and receiving antennas 4h1-4h4 are formed on a transparent substrate 25 by transparent wiring using transparent electrodes such as ITO. The pattern of the receiving antennas 4h1-4h4 surrounds the pattern of the transmitting antennas 3h1-3h4 and is formed in a concentric circular arc shape across the two sides at the corner of the transparent substrate 25.

  The transmission antenna 3h1 and the reception antenna 4h1, the transmission antenna 3h2 and the reception antenna 4h2, the transmission antenna 3h3 and the reception antenna 4h3, and the transmission antenna 3h4 and the reception antenna 4h4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 29, only wiring from the transmitting antenna 3h1 and the receiving antenna 4h1 is shown.

  In FIG. 29, the boundary of the display portion of the display is indicated by B. The boundary B of the display unit is located inward from the end of the transparent substrate 25 by a predetermined length. Further, the center C1-C4 of the arcs of the transmitting antennas 3h1-3h4 and the receiving antennas 4h1-4h4 are respectively located at the corners of the display unit. The transmission antennas 3h1-3h4 and the reception antennas 4h1-4h4 are arcs larger than ¼, and are formed beyond the boundary B of the display unit to the end of the transparent substrate 25.

  Thus, in the antenna having the configuration shown in FIG. 29, compared to the antenna formed by the ¼ arc shown in FIG. It becomes possible to detect.

  FIG. 30 shows a fourth configuration example of the transmitting antenna 3 and the receiving antenna 4 formed using a transparent electrode on a transparent substrate. In the configuration of the antenna shown in FIG. 30, the transmitting antenna 3 i 1-3 i 4 and the receiving antenna 4 i 1-4 i 4 each have a double quarter by transparent wiring using a transparent electrode such as ITO on the transparent substrate 25. It is formed with an arc-shaped pattern. The pattern of the receiving antennas 4g1-4g4 surrounds the pattern of the transmitting antennas 3g1-3g4, and is formed in a concentric circular arc shape at the corner of the boundary B of the display unit.

  The transmitting antenna 3i1 and the receiving antenna 4i1, the transmitting antenna 3i2 and the receiving antenna 4i2, the transmitting antenna 3i3 and the receiving antenna 4i3, and the transmitting antenna 3i4 and the receiving antenna 4i4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 30, only the wiring from the transmitting antenna 3i1 and the receiving antenna 4i1 is shown.

In the antenna having the configuration shown in FIG. 30, the transmission antennas 3i1-3i4 and the reception antennas 4i1-4i4 are each formed in a double ¼ arc-shaped pattern, so that the reception sensitivity of the antenna can be improved. It becomes. The reception sensitivity of the antenna can be improved by increasing the number of arc-shaped pattern rings of each antenna.
FIG. 30 shows an example in which both the transmission antenna and the reception antenna are formed with a double arc pattern. However, only one of the antennas may be formed with a double arc pattern. Further, one or both of the transmission antenna and the reception antenna may be formed in a triple or more arc pattern.

FIG. 31 shows a fifth configuration example of the transmission antenna 3 and the reception antenna 4 formed using a transparent electrode on a transparent substrate.
In the configuration of the antenna shown in FIG. 31, similarly to FIG. 30, the transmitting antenna 3j1-3j4 and the receiving antenna 4j1-4j4 are respectively formed by transparent wiring using transparent electrodes such as ITO at the corners of the transparent substrate 25. It is formed of a double quarter arc pattern.

  The transmitting antenna 3j1 and the receiving antenna 4j1, the transmitting antenna 3j2 and the receiving antenna 4j2, the transmitting antenna 3j3 and the receiving antenna 4j3, and the transmitting antenna 3j4 and the receiving antenna 4j4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 31, only the wiring from the transmitting antenna 3j1 and the receiving antenna 4j1 is shown.

The antenna configuration shown in FIG. 31 further includes transmission antennas 3j5-3j6 and reception antennas 4j5-4j6 formed in a double half arc pattern on the side of the transparent substrate 25. The pattern of the receiving antennas 4j5-4j6 surrounds the pattern of the transmitting antennas 3j5-3j6 and is formed in a concentric circular arc shape at the corner of the boundary B of the display unit.
The transmission antenna 3j5 and the reception antenna 4j5, and the transmission antenna 3j6 and the reception antenna 4j6 are respectively connected to circuit units constituting separate proximity sensors.

  With the configuration as shown in FIG. 31, it is possible to detect an object in a wider inspection region as compared with the configurations of FIGS. 27 to 30 in which the antennas are arranged only at the corners of the transparent substrate. Become. FIG. 31 shows an example in which both the transmitting antenna and the receiving antenna are formed with a double arc pattern, but either one or both antennas may be formed with one arc pattern. 27 to 31 show an example in which the reception antenna 4 is formed surrounding the transmission antenna 3, the transmission antenna 3 may be formed surrounding the reception antenna 4.

  In the antenna configuration shown in FIG. 32, the transmission antennas 3D, 3L, 3U, and 3R are arranged in a divided ring shape, and the point-shaped reception antennas 4D, 4L, 4U, and 4R are arranged at positions facing these. Is. By using four sets of proximity sensors as shown in FIG. 1, the position detection device can be configured similarly to the antenna configuration shown in FIG.

  Here, when a detailed experiment is performed on the center position of the sensitivity of the set of the ring antenna 4 and the point antenna 3 shown in FIG. 22 with respect to the circuit shown in FIG. 3 position.

  In the ring-shaped and point-shaped transmission / reception antennas, the sensitivity as a proximity sensor improves as the radius of the ring increases. Conversely, if the size of the ring is reduced, the sensitivity as a proximity sensor decreases. Therefore, the size of the ring cannot be made too small. In Example 4, according to the experimental results using the simple ring and the pointed antenna shown in FIG. 22, in the proximity sensor operated with the 5V power source, when the radius of the ring is 1 cm, as shown in FIG. An effective sensitivity distance of about 5 cm can be realized. If this effective sensitivity distance is required, the ring antenna needs to have a diameter of about 1 cm.

On the other hand, when the position of the point antenna 3 relative to the ring antenna 4 is moved from the center position of the ring antenna 4 as shown in FIG. Moved to position. This indicates that the arrangement of the antenna set can be changed only by changing the position of the point antenna 3 without changing the position of the ring antenna 4. The configuration of the antenna using the fact that the antenna set arrangement can be changed by changing the position of the point-like antenna located inside the ring-shaped antenna will be described below.

  FIG. 34 shows an example of an antenna configuration used for the proximity sensor 1X of the fifth embodiment shown in FIG. The configuration shown in FIG. 34 shows a state in which the transmitting antenna 3 is a ring antenna, the receiving antennas 4R, 4L, 4U, and 4D are dot antennas, and the distance between the vertically opposing left and right is set as d. It was. In this configuration, in the case of the circuit of FIG. 9, the antenna occupies despite the fact that the transmission / reception antennas of the four sets of proximity sensors are arranged approximately 1 cm apart by bringing the value of d close to the diameter of the ring antenna 3. The area of about 1 cm in diameter is sufficient.

  FIG. 35 is an example of an antenna configuration used for the proximity sensor 1Y of the sixth embodiment shown in FIG. In the configuration shown in FIG. 35, the reception antenna 4 is a ring antenna, the transmission antennas 4R, 4L, 4U, and 4D are dot antennas, and the distance between each of the antennas facing each other vertically and horizontally is shown as d. It was. In this configuration, in the case of the circuit of FIG. 10, the antenna occupies despite the fact that the transmission / reception antennas of the four sets of proximity sensors are arranged approximately 1 cm apart by bringing the value of d close to the diameter of the ring antenna 4. The area of about 1 cm in diameter is sufficient.

  In the antenna configuration shown in FIG. 32, the sensitivity of each antenna is not sufficiently symmetrical, and the condition that the sensitivity of the proximity sensor depends only on the distance cannot be satisfied. However, with the antenna configuration shown in FIGS. 34 and 35, a plurality of antennas having good symmetry of sensitivity output can be arranged apart from each other in a narrow region, and a configuration in which the sensitivity of the proximity sensor depends only on the distance can be realized. it can.

  With the position detection device using the antenna configuration shown in FIGS. 34 and 35, it is possible to give a direction instruction or input function to one non-contact button as a spatial input device. The concept of a button generally defines its existence area as a limited small area. In the fifth embodiment, it is assumed that this area has a size of about 1 square cm.

  If the diameter of the ring antenna is 1 cm and the number of proximity sensors required for motion detection in the two directions is four, the four ring antennas must be housed in one button. Even if the center of the ring antenna is arranged at the apex of the square, the size of the button needs to be at least 2 cm square. In this case, the distance between the virtual centers of the antenna sets of the four proximity sensors is about 1 cm.

  In the proximity sensor of the present invention, a transmission antenna and a reception antenna formed with transparent electrodes on a transparent substrate are used as shown in FIG. 27 to FIG. It is possible to configure a position detection device that detects the position of the test object located in the three-dimensional region. The input device can be configured by controlling the input to the device in accordance with the three-dimensional position information of the object to be examined by this position detection device. In addition, a position detecting device having a plurality of antennas that provide sensitivity depending almost only on a distance in a small region as indicated by the concept of a button can be configured by the configuration shown in FIGS. 33 to 35. it can.

1a, 1b, 1c, 1d, 1X, 1Y, 1Z, 1U, 1V, 1W, 2a, 2b, 2c, 2d proximity sensor 2 oscillator 3, 3a, 3b, 3c, 3d, 3f, 3g1-3g4, 3h1-3h4 3i1-3i4, 3j1-3j6 Transmitting antenna 4, 4a, 4b, 4c, 4d, 4e, 4f, 4g1-4g4, 4h1-4h4, 4i1-4i4, 4j1-4j6 Receiving antenna 5, 5S Parasitic capacitance or capacitor 6, 6D, 6L, 6R, 6U Buffer 6S1, 6S2 Amplifier 7, 7D, 7L, 7R, 7U, 7T Resistor 7M, 7LT Inductor 8, 8D, 8L, 8R, 8U Amplifier 9 Phase detector 10 LPF
DESCRIPTION OF SYMBOLS 11 Output terminal 12 Adder circuit 13A, 13B Frequency divider 14 Logarithmic amplifier circuit 15, 16 Shield 17 Transistor 18 Operational amplifier 19 Resistance 25 Transparent substrate 27 Connection terminal 28 Connection terminal 30 Booster circuit 31 Amplification circuit 102 Oscillator 103 Transmission antenna 104 Reception antenna 107 Resistor 108 Capacitor 109 Phase detector 110 LPF
111 Output terminal

Claims (11)

An AC signal source;
A transmission antenna that transmits radio waves based on a signal from the AC signal generation source;
A receiving antenna for receiving radio waves,
First phase-shifting means for phase-shifting a signal from the AC signal source;
Combining means for combining the signal phase-shifted by the first phase-shifting means and the signal received by the receiving antenna;
And a phase detection means for detecting a phase of the synthesized signal synthesized by the synthesis means using a signal of the AC signal generation source. The proximity sensor according to claim 1, further comprising: a resistor or an inductor that connects the transmitting antenna and the combining unit as the first phase shifting unit. In accordance with the amount of phase shift by the first phase shift means and the receiving antenna, the second phase shift means for phase shifting the signal from the AC signal generation source,
3. The proximity sensor according to claim 1 , wherein the phase detection unit performs phase shift detection on the synthesized signal synthesized by the synthesis unit using the signal phase-shifted by the second phase shifting unit. . Said phase detecting means, the binarized said composite signal, as claimed in any one of claims 1 to 3, characterized in that the phase detection in the binarized signal of the AC signal generating source Proximity sensor. The proximity sensor according to any one of claims 1 to 4 , further comprising a resistor that connects the receiving antenna and a reference potential. Proximity sensor according to claim 1, any one of 5, characterized in that it comprises a resistor and an inductor connecting the receiving antenna and the reference potential. A first amplifier for amplifying a signal received by the receiving antenna;
A second amplifier for amplifying the signal phase-shifted by the first phase-shifting means,
As the combining means, the proximity sensor according to claim 5 or 6, characterized in that it comprises an adder for adding the signal amplified by said first amplifier and said second amplifier. Between the AC signal generation source and the transmitting antenna,
Boosting means for boosting the power supply of the circuit of the AC signal generation source;
The proximity sensor according to any one of claims 1 to 7 , further comprising: an amplifying unit that amplifies a signal of the AC signal generation source by a power supply system boosted by the boosting unit. The proximity sensor according to any one of claims 1 to 8 , further comprising a frequency divider between the AC signal generation source and the transmission antenna. The proximity sensor according to claim 9 , further comprising shielding means for shielding radio waves emitted from the AC signal generation source. The proximity sensor according to any one of claims 1 to 10 , further comprising a logarithmic amplifier circuit in a subsequent stage of the phase shift detection means.

Images