JP2006234697A - Position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a signal processing circuit for position control of a measured object. <P>SOLUTION: This position detector 1 comprises an absolute position detection sensor 2 for outputting a fact that the measured object 10 moves to a predetermined position as variation in output signal level, a relative position detecting sensor 3 for outputting a moving amount of the measured object 10 with the number of pulses of the output signal, and a signal processing section 4 for generating one output signal from the absolute position detection signal which is an output signal of an absolute position detection sensor 2 and a relative position detection signal which is an output signal of the relative position detecting sensor 3. The position detector 1 detects a relative distance from the predetermined position of the measured object 10 by measuring the number of pulses of a compound position detecting signal with reference to the position where the compound position detection signal varies to a value higher or lower than a predetermined level. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a position detection device that performs signal processing on a position detection signal output from a position detection sensor that detects the position of an object to be measured, and measures the position of the object to be measured based on the position detection signal after the signal processing. .

  Various signal processing circuits that process detection signals from sensors and switches have been proposed (see Patent Documents 1 to 8).

Among them, the technique described in Patent Document 1 controls a plurality of analog switches, and a divided voltage value (a type of detection signal) according to the control of the analog switches is used as a subsequent A / D (analog-digital). The voltage is input to the microcomputer via the converter, the divided voltage value is compared with a set value, and the on / off states of the plurality of analog switches are determined from the comparison result.
The technique described in Patent Document 2 controls a plurality of switches and inputs a voltage value (a kind of detection signal) by the control of the switches to an A / D converter in the microcomputer. The present invention relates to a method for generating one voltage value for accurately detecting multiple operations of the switches.
The technology described in Patent Document 3 relates to the sharing of a microcomputer terminal so that a signal to be A / D converted (a signal that can be used as a detection signal) and an interrupt signal can be captured from a common terminal. It is to be switched with a switch.
The technique described in A / D Patent Document 4 relates to a signal processing circuit of a digital oscilloscope, and before inputting a signal (a type of detection signal) applied to its input terminal to the A / D conversion circuit, By amplifying the signal by dividing it into an alternating current component and a direct current component, both the direct current characteristics and the broadband characteristics of the signal path are achieved.

  These techniques described in Patent Documents 1 to 4 basically process one detection signal (or a signal based on one detection signal), thereby reducing the number of signal transmission lines. In addition, the number of input terminals of the subsequent processing circuit is reduced, or the accuracy and characteristics of signal processing are improved.

On the other hand, in the techniques described in Patent Documents 5 and 7, signal processing is performed on two detection signals.
In the technique described in Patent Document 5, two signals are detected so that the resolution of the A / D converter at the subsequent stage may be low when obtaining a signal proportional to the ratio of the sum signal and the difference signal of the two detection signals. A desired result can be obtained by one of the signals and the sum signal.
The technique described in Patent Document 6 relates to a coordinate input device such as a digitizer, and switches between two detection signals, that is, an X coordinate signal and a Y coordinate signal by a switching connection circuit to differentially amplify the X coordinate signal and the Y coordinate. The signal is A / D converted sequentially.

By the way, position control of a lens in a camera or the like is known as performing position control of an object to be measured using two detection signals.
In the lens position control unit, a relative position sensor that detects a relative position and outputs a relative position detection signal according to an actuator operation, for example, rotation of a DC motor, and a mechanical absolute position of the lens are usually detected. And an absolute position detection sensor for outputting an absolute position detection signal. Then, based on the output change of the absolute position detection sensor, the output position of the relative position detection sensor is counted, the lens is moved to the target position, and the lens position is controlled by stopping.

In applications such as lens position control, particularly miniaturization and low cost are required.
As described above, when a rotary encoder or an optical scale using moire interference fringes is used as a relative position detection sensor linked to the movement of an actuator such as a DC motor, the structure is simple and inexpensive. is there. In particular, when a rotary encoder uses an analog device such as a photo interrupter as its rotation detection device, its structure is simple and inexpensive.
As the absolute position detection sensor, if a mechanical switch or a non-contact optical sensor such as a photo interrupter or a photo reflector is used, its structure is simple and inexpensive.

The relative position detection sensor and the absolute position detection sensor employed to make the lens position control unit simple and inexpensive usually output an analog signal. Therefore, in order to measure and control the lens position by a central processing unit (CPU) or the like based on these sensor outputs, an A / D converter (or an amplifier for amplifying the sensor output and quantizing the analog signal) (or , Its function) is required. Since high quantization accuracy is not necessary in this application, the A / D conversion function in the CPU is usually used to A / D convert the relative position detection signal and the absolute position detection signal, respectively, and after A / D conversion. Based on this signal, feedback control of a motor or the like serving as an actuator is performed.
JP 08-201889 A JP 09-270685 A Japanese Patent Laid-Open No. 06-036056 Japanese Patent Laid-Open No. 06-197019 Japanese Patent Laid-Open No. 03-263619 Japanese Patent Laid-Open No. 02-260023

  When the two position detection sensors are A / D converted by the CPU as described above, two signal transmission lines are required, and two A / D conversion ports need to be secured in the CPU. Further, since it is necessary to A / D convert two sensor outputs at the same time, the load on the CPU is heavy, and the position detection is delayed with respect to the control of the drive source (actuator).

  Further, for example, in the case of a camera that processes the above signals using the A / D conversion port of the CPU, some A / D conversion channels are only about 4 channels in an inexpensive CPU. In the case of a camera, A / D conversion ports required by the CPU on the system include not only lens position control but also environmental temperature detection, battery temperature detection, and battery voltage detection. Assuming these, the number of A / D conversion ports is not sufficient, and it is necessary to reduce the number of A / D ports used for lens control as much as possible. Further, increasing the number of A / D conversion ports is not preferable because the system cost of the camera increases accordingly.

It should be noted that the signal processing technology (Patent Documents 5 and 6) for the two detection signals described above cannot be applied to the use of such position detection control of a lens or the like for the following reason.
Since Patent Document 5 obtains a signal proportional to the ratio of the difference signal between two detection signals and the sum signal, it specializes in servo control of an optical disk, for example. Patent Document 6 relates to a coordinate input device, and in particular, two detection signals (X coordinate signal and Y coordinate signal) are differentially amplified one by one and sequentially A / D converted. If a method similar to this is applied to the position control of a lens or the like, the control response is deteriorated, so this method cannot be used for a camera or the like.

  The problem to be solved by the present invention is to improve a signal processing circuit for controlling the position of an object to be measured.

The position detection device according to the present invention outputs an absolute position detection sensor that outputs a change in the level of an output signal that the object to be measured has moved to a predetermined position, and outputs the amount of movement of the object to be measured by the number of pulses of the output signal. One output signal is generated as a composite position detection signal from the relative position detection sensor, the absolute position detection signal that is an output signal of the absolute position detection sensor, and the relative position detection signal that is an output signal of the relative position detection sensor. A signal processing unit, and by measuring the number of pulses of the composite position detection signal based on a position where the composite position detection signal has changed to a predetermined level or higher or below, The relative distance of is detected.
Another position detection apparatus according to the present invention includes an absolute position detection sensor that outputs a change in the level of an output signal that the object to be measured has moved to a predetermined position, and a movement amount of the object to be measured by the number of pulses of the output signal. One output signal from the output relative position detection sensor, the absolute position detection signal that is the output signal of the absolute position detection sensor, and the relative position detection signal that is the output signal of the relative position detection sensor is used as a composite position detection signal. A signal processing unit that generates the composite position detection signal based on a peak level, a bottom level of the composite position detection signal, or a position at which a change in a predetermined level specified by the peak level and the bottom level is detected. The relative distance from the predetermined position of the object to be measured is detected by measuring the number of pulses.

Preferably, the signal processing unit generates the composite position detection signal which is the one signal by performing differential amplification processing on the relative position detection signal and the absolute position detection signal.
Alternatively, preferably, the signal processing unit generates the composite position detection signal which is the one signal by performing amplitude modulation of the carrier wave with the absolute position detection signal using the relative position detection signal as a carrier wave.
Preferably, the dynamic range of the composite position detection signal is X (V), the amplitude range of the absolute position detection signal is A (V), the amplitude range of the relative position detection signal is B (V), and the relative position detection signal is When the noise level is Wn (V), the following (1) and (2) are satisfied.
(1) X> A + B
(2) A> B + Wn

  In the signal processing apparatus according to the present invention, the signal processing circuit can be improved for controlling the position of the object to be measured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration example of a position detection device for position detection according to an embodiment of the present invention.
As shown in FIG. 1, the position detection device 1 detects two positions detection sensors, that is, an absolute position for detecting an absolute position of the object to be measured and outputs an absolute position detection signal Sa in order to measure the position of the object 10 to be measured. It has a detection sensor 2 and a relative position detection sensor 3 that detects a relative position of a non-measurement object and outputs a relative position detection signal Sr. Here, the “absolute position” means a position indicating the reference or starting point of the relative position, and the position of the object to be measured is determined by the amount of change in the relative position from the absolute position.

  The position detection apparatus 1 includes a signal processing circuit 4 that outputs one signal (hereinafter referred to as a composite position detection signal) Sd from the absolute position detection signal Sa and the relative position detection signal Sr, and the position of the object to be measured from the position detection signal. And a central processing unit (CPU) 5 as a position detection unit for measuring. The CPU 5 has an A / D conversion function (for convenience, displayed by the A / D conversion unit 5A in FIG. 1), and the composite position detection signal Sd is input to the A / D conversion unit 5A. Sd is converted into a digital signal, and digital signal processing for position detection is executed by a function in the CPU (not shown).

FIG. 2A shows the waveform of the absolute position detection signal Sa, and FIG. 2B shows the waveform of the relative position detection signal Sr. In these figures, the horizontal axis represents time t and the vertical axis represents the level L of each detection signal.
The absolute position detection signal Sa changes from, for example, the L (Low) level to the H (High) level as shown in FIG. 2 (A) as the DUT 10 shown in FIG. 1 moves in a certain direction. Signal. On the contrary, the absolute position detection signal Sa may be a signal that changes from the H level to the L level. As the absolute position detection sensor 2 shown in FIG. 1 that outputs such an absolute position detection signal Sa, a mechanical sensor, for example, a state in which the sensor section is in contact with the object to be measured 10 or a non-contact state, or vice versa. Alternatively, a switch whose output level changes in a contact state from a non-contact state may be used. However, since the mechanical sensor generates a load and affects the drive system, the magnitude of the load changes with time, and the detection position fluctuates due to mechanical tolerance. Therefore, the absolute position detection sensor 2 is optical. A sensor is desirable. A photo interrupter or a photo reflector can be used as the optical sensor.

  On the other hand, as shown in FIG. 2B, the relative position detection signal Sr varies somewhat in amplitude depending on the magnitude of noise, but basically a periodic signal having a constant amplitude is desirable. The relative position detection sensor 3 shown in FIG. 1 that outputs such a relative position detection signal Sr (analog waveform) may be, for example, an optical scale or a magnetic scale using moire interference fringes. An analog encoder is desirable. The analog encoder and the photo interrupter will be described later.

  Next, a more specific configuration and operation will be described.

FIG. 3 shows a signal processing circuit 4 that superimposes the absolute position detection signal Sa and the relative position detection signal Sr by amplitude modulation.
The signal processing circuit 4 shown in FIG. 3 has a function of amplifying and amplifying two analog signals by the amplitude modulation method used in the AM radio (“Mod” in FIG. . & Amp. ”). The amplitude-modulated and amplified signal is input to the DA conversion port AD1 of the CPU 5 as the composite position detection signal Sd.

  FIG. 4C shows a waveform of the composite position detection signal Sd generated by amplitude modulation and amplification with the configuration shown in FIG. 4A shows the waveform of the absolute position detection signal Sa, and FIG. 4B shows the waveform of the relative position detection signal Sr. The vertical and horizontal axes in these figures are the same as those in FIG. 2 described above, and the signal level L and time t are the same scale in the three figures.

  As apparent from comparing FIG. 4C with FIG. 4A and FIG. 4B, the composite position detection signal Sd is an output waveform of the relative position detection sensor (relative position detection signal Sr: FIG. B)) is used as a carrier wave, and amplitude modulation is performed using the output of the absolute position detection sensor (absolute position detection signal Sa: FIG. 4A) as a signal waveform (peak-to-peak value of the signal). In the composite position detection signal Sd, the output of the absolute position detection sensor appears as an amplitude, and the repetition cycle of the output of the relative position detection sensor is maintained as it is in the composite position detection signal Sd. As a result, information of two analog signals can be represented by one analog quantity.

FIG. 5 shows another configuration example of the signal processing circuit 4 that generates the composite position detection signal Sd by changing the DC level of the relative position detection signal by differential amplification.
The signal processing circuit 4 shown in FIG. 5 inputs the absolute position detection signal Sa to one differential input (for example, “+” input) and the relative position detection signal Sr to the other differential input (for example, “−” input). , And a differential amplifier (D.Amp) 4A that amplifies the difference with a predetermined gain, and an amplifier (Amp.) That amplifies the relative position detection signal Sr with a predetermined gain and outputs the amplified signal to the differential amplifier 4A. 4B. The composite position detection signal Sd is output from the output of the differential amplifier 4A and input to the DA conversion port AD1 of the CPU 5.

  FIG. 6C shows a waveform of the composite position detection signal Sd generated by differential amplification with the configuration shown in FIG. FIG. 6A shows the waveform of the absolute position detection signal Sa, and FIG. 6B shows the waveform of the relative position detection signal Sr. The vertical and horizontal axes in these figures are the same as in FIG. 2 described above, and the signal level L and time t are the same scale in the three figures. However, for the sake of drawing, the gain of the differential amplifier 4A and the gain of the amplifier 4B shown in FIG. 5 are set to “1” to represent the composite position detection signal Sd of FIG.

  As shown in FIG. 6 (C), instead of amplitude modulation, even if the output of the absolute position detection sensor is DC-shifted with respect to the output of the relative position detection sensor, one output is obtained as in FIG. 4 (C). Information of two analog signals can be expressed by analog quantities.

Here, the gain of the differential amplifier 4A and the gain of the amplifier 4B shown in FIG. 5 can be determined as follows. This method of determining the gain can also be applied when a signal before amplitude modulation is amplified in the signal processing circuit 4 shown in FIG.
For example, in the case of a rotary analog encoder, the relative position detection signal Sr is obtained by detecting light that passes through the slits of the rotating body and is blocked by the rotating body portion between the slits by the light receiving unit. The slits of the rotator are accurately formed at a predetermined cycle in the circumferential direction, but the amplitude of the position detection signal Sr varies somewhat due to shaft shake or deformation of the rotator. Due to such minute fluctuations and superimposed noise in the signal path, the noise level of the relative position detection signal Sr is as shown in the waveform Sd1 before the absolute position detection in FIG. 4 (C) (or FIG. 6 (C)). It fluctuates with a certain width Wn.
It is necessary to provide the absolute level detection level at a position further away from the maximum change point of the noise level, that is, on a smaller side (or a larger side) as a level at a position separated by a certain margin Wd or more. Further, this detection level needs to be set in the middle of a level change that is separated from the H level of the absolute position detection signal by a sufficient margin, as indicated by Ld in FIG. 4 (A) (or FIG. 6 (A)). .
If each margin for the waveforms Sd1 and Sd2 of this detection level is smaller than the required value Wd, the noise level of the waveform Sd1 before absolute position detection shown in FIG. 4C (or FIG. 6C), or the absolute The detection level may overlap the noise level of the waveform Sd2 after position detection, and the absolute position may be erroneously detected due to noise. Although it is necessary to set the detection level appropriately in order to prevent such a malfunction, the settable range is expanded by adjusting the relative gain between the absolute position detection signal Sa and the relative position detection signal Sr. Can do.
In the configuration shown in FIG. 3, it is desirable to set the gain of the differential amplifier 4A to a value larger than 1 for the purpose of relatively suppressing the noise level. On the other hand, the gain of the amplifier 4B is desirably set to an appropriate value of 1 or more or less than 1 from the viewpoint of expanding the range for preventing the malfunction. In order to obtain the same effect, contrary to FIG. 3, the absolute position detection signal Sa may be amplified, or both the absolute position detection signal Sa and the relative position detection signal Sr may be amplified with different gains. Good.

In the present embodiment, a method of measuring the number of pulses of the composite position detection signal Sd based on the position where the composite position detection signal Sd has changed to a predetermined level or higher or below, and the peak level and bottom level of the composite position detection signal Sd. Alternatively, there is a method of measuring the number of pulses of the composite position detection signal Sd based on a position where a change in a predetermined level specified by the peak level and the bottom level is detected.

In any method, the dynamic range of the composite position detection signal Sd is X (V), the amplitude range of the absolute position detection signal Sa is A (V), the amplitude range of the relative position detection signal Sr is B (V), and the relative position When the noise level of the detection signal Sr is Wn (V), it is desirable to satisfy the following (1) and (2).
(1) X> A + B
(2) A> B + Wn

  This prescribes an example of a condition for performing reliable absolute position detection. Thereby, as shown in FIG. 12C, it is possible to detect the absolute position at a level where the waveforms Sd1 and Ds2 do not overlap while considering the noise level. Alternatively, it is possible to reliably detect that the absolute position has been reached even when shifting at the bottom level.

  The detection signal Sd generated in this way is A / D converted in the CPU 5 shown in FIG. 3 or FIG. 5, and uses an arithmetic function for performing comparison in the CPU and a data holding function such as a register, Detection of the level change extreme point (hereinafter simply referred to as “peak” including the positive electrode peak and the negative electrode peak) is performed.

FIG. 7 schematically shows a peak detection method. Although actual peak detection is performed on digital data, in FIG. 7, the waveform level change is shown as an analog amount for convenience.
In general, an amplitude-modulated signal needs to be demodulated by a demodulation processing circuit before being processed. On the other hand, in this example, the amplitude-modulated signal (composite position detection signal Sd) maintains the period of the original relative position detection signal Sr as it is, so that the pulse of the composite position detection signal Sd is detected after the absolute position is detected. If the number is counted by, for example, the number of peaks, the position of the DUT 10 (FIG. 1) can be detected by the CPU 5 shown in FIG. 3 or 5 without performing demodulation processing.

As shown in FIG. 7, the peak value of the position detection signal Sd is constantly monitored, and peak detection is performed. The positive peak is detected when the signal level decreases from the peak level to a value greater than the noise cancellation level, and the negative peak is detected when the signal level increases from the peak level to a level higher than the noise cancellation level.
In FIG. 7, the counter value in the CPU is incremented with..., N−1, n, n + 1, n + 2,. In this example, after the counter value reaches n in the middle, the signal level reaches the absolute value detection level Ldh on the high side, whereby the absolute position is detected. When the absolute position is detected, the counter value is reset, or another counter value starts counting the number of peak detections, and the object to be measured is based on the number of peak detections newly started from this absolute position. Ten position measurements are started.
Thereby, for example, when the counter value corresponding to the desired position is reached, it is possible to perform control such as stopping the movement of the DUT 10.

In the position detection method described above, the amplitude fluctuation range corresponds to the output of the absolute position detection sensor, and the period of the waveform does not change in the output of the relative position detection sensor. For this reason, when the output of the relative position detection sensor is detected by the number of detected peaks as described above, the amplitude fluctuation does not affect the relative position detection. Therefore, although the configuration of the signal processing unit 3 is simple, position detection with high detection accuracy and signal processing therefor are possible.
Further, as shown in FIG. 8, the detection signal Sa and Sr are respectively amplified (Amp.) And then compared to a comparative example in which the signals are input to other A / D conversion ports AD1 and AD2 in the CPU. In the position detection method of the embodiment, only one A / D conversion port is used, and an inexpensive CPU can be used accordingly.

  Next, an embodiment in which the lens position is controlled by applying the above position detection method will be described.

  The lens of the camera is composed of lens groups that are arranged in order along the optical axis from the front end side of the lens barrel toward the image sensor side and have various roles. For example, according to a certain lens configuration, a first group lens for focusing, a second group lens for performing zooming, which is arranged on the front end side of the lens barrel, can correctly focus on the imaging surface after zooming operation. And a fourth group lens for forming an image on the imaging surface. Which lens group is movable and which is fixed varies, but generally, the second group lens and the fourth group lens are movable and the others are fixed, and the second group lens and the third group lens are movable. There are things that fix others, in addition to this, those that make the first group lens movable, those that omit the third group lens, and that make the rear part of the second group lens and the fourth group lens (image sensor side) movable .

In this embodiment, the movable lens group is uniaxially moved using the object to be measured (moving unit).
FIG. 9 illustrates a drive system for moving the moving unit and a configuration for position detection.
The moving unit 11 that accommodates the lens group has a screw hole whose inner surface is machined, and the drive shaft 12 is passed through the screw hole. The drive shaft 12 has a male screw formed on the outer periphery thereof, which is screwed with the female screw of the screw hole of the moving unit, and the moving unit 11 moves in the direction of the arrow shown in FIG. 9 as the drive shaft 12 rotates. It is like that. Although not particularly shown, the moving unit 11 can be smoothly slid by a guide mechanism that is also received by a lens barrel (not shown).

  A drive shaft pulley 12A is fixed to one end of the drive shaft 12, and the drive shaft pulley 12A is connected to a motor-side pulley 13A fixed to the shaft of the motor (M) 13 by a belt or a gear. The rotational driving force of the motor 13 is transmitted by the motor side pulley 13A and the driving shaft pulley 12A to rotate the driving shaft 12. The motor 13 is driven by a motor driver 14 under the control of the CPU or the like shown in FIG.

  An analog encoder turntable 15 having a notch (or slit hole) in the circumferential direction is fixed to the other end of the drive shaft 12. As the drive shaft 12 rotates, the turntable 15 also rotates, its notch (or slit hole) periodically passes the light from the photointerrupter 16, and its optical path periodically changes. The periodic relative position detection signal Sr is obtained from the output of the photo interrupter 16. The rotating plate 15 can be substituted by providing a notch or a slit hole in the drive shaft pulley 12A or the motor side pulley 13A. In this case, the photo interrupter 16 is close to the drive shaft pulley 12A or the motor side pulley 13A. Be placed.

FIG. 10 shows an equivalent circuit of the photo interrupter 16.
The light emitting diode Di is connected between the voltage supply line and the GND level via the resistor R1. When power is supplied to the light emitting diode during position detection, the light emitting diode Di emits light. The light is received by a photodetector (transistor T). The photodetector is connected between the voltage supply line and the GND line via a load resistor RL. When the charge photoelectrically converted by light reception flows according to the potential gradient, the potential at the midpoint of connection between the photodetector and the load resistor RL is fluctuate. This potential fluctuation occurs when the rotating disk 15 (FIG. 9) moves through the space between the photodetector and the light emitting diode, and the light is passed and blocked according to the rotation. As a result, the periodic relative position detection signal Sr shown in FIG. 11A is output from the photo interrupter 16.

  On the other hand, the moving unit 11 shown in FIG. 9 is provided with a shielding scale 11A that is long in the moving direction. Another photo interrupter 17 of an equivalent circuit similar to that shown in FIG. For this reason, the photo interrupter 17 maintains the L level while the light from the light emitting diode is blocked by the shielding scale 11A, and transitions to the H level when the light is not blocked, as shown in FIG. An absolute position detection signal Sa having a waveform is output.

The absolute position detection signal Sa and the relative position detection signal Sr are output to the signal processing circuit 4 shown in FIG. 1, and one composite position detection signal Sd is generated by the configuration shown in FIG. 3 or FIG.
Thereafter, the composite position detection signal Sd input to the CPU 5 is A / D converted there. In addition, noise or mechanical vibration also occurs in A / D conversion, and fluctuations are expected to some extent. Therefore, a process for providing a change determination value and providing a noise canceling function is provided so as not to make an erroneous determination due to these. It is desirable to do.
After the A / D conversion, the absolute position is detected according to the change in the peak level of the signal as described above, and the position detection of the mobile unit 11 shown in FIG. 9 is started by counting the number of detected peaks thereafter. The control target value is input to the CPU 5 in advance by manual operation or a distance measurement result at the time of autofocus, and is stored therein. When the moving unit 11 reaches or just before the control target value, the CPU 5 issues a stop instruction to the motor driver 14, and as a result, the motor 13 stops and the lens position control ends.

  In this embodiment, for example, absolute position detection and relative position detection can be performed by a simple actuator 16 whose equivalent circuit is shown in FIG. 10, and there is an advantage that the configuration of the lens position control unit is simple and can be manufactured at low cost. In addition, as described above, the lens position can be detected with high detection accuracy even though the configuration is simple, and there is only one A / D conversion port of the CPU 5 to be used. Can be employed.

According to the present embodiment, despite the simple configuration of the signal processing unit described above, position detection with high detection accuracy and signal processing therefor can be performed, and the number of AD conversion ports can be reduced. In addition, the following advantages can be obtained.
When detecting the absolute position based on the position where the composite position detection signal has changed to a level above or below a predetermined level, the peak level of the composite position detection signal, the bottom level, or the change in the predetermined level specified by the peak level and the bottom level are detected. In the case of detection, the absolute position can be detected at the midpoint level of the composite position detection signal as the specified predetermined level.
In the above two methods, if the above conditions (1) and (2) are satisfied at the same time, position detection can be performed at a stable level without the influence of repeated waveforms and noise. Further, even when shifting at the bottom level, it can be reliably detected that the absolute position has been reached. For this reason, position detection with higher detection accuracy and signal processing therefor are possible.

  The present invention is widely applied to applications in which a position detection signal output from a position detection sensor that detects the position of an object to be measured is processed, and the position of the object to be measured is measured based on the position detection signal after the signal processing. it can.

It is a block diagram which shows the example of 1 structure of the signal processing apparatus for the position detection in embodiment of this invention. (A) is a waveform diagram of an absolute position detection signal, and (B) is a waveform diagram of a relative position detection signal. It is a block diagram provided with the signal processing part which superimposes an absolute position detection signal and a relative position detection signal by amplitude modulation. (A) is a waveform diagram of an absolute position detection signal, (B) is a waveform diagram of a relative position detection signal, and (C) is a waveform diagram of a position detection signal generated by amplitude modulation and amplification in the configuration shown in FIG. is there. It is a circuit block diagram which shows the other structural example of the signal processing circuit 4 which produces | generates a position detection signal by changing the direct current | flow level of a relative position detection signal by differential amplification. (A) is a waveform diagram of an absolute position detection signal, (B) is a waveform diagram of a relative position detection signal, and (C) is a waveform diagram of a position detection signal generated by differential amplification in the configuration shown in FIG. . It is a figure which shows the peak detection method typically. It is a block diagram which shows the comparative example input into another A / D conversion port in CPU, after amplifying each detection signal, respectively. In an Example, it is a figure which shows the structure for the drive system which moves a movement unit, and a position detection. It is the equivalent circuit schematic of the photo interrupter used in the Example. (A) is a waveform diagram of a relative position detection signal output from a photo interrupter, and (B) is a waveform diagram of an absolute position detection signal. (A) is a waveform diagram of an absolute position detection signal, (B) is a waveform diagram of a relative position detection signal, and (C) is another waveform diagram of a position detection signal generated by differential amplification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Signal processing circuit, 2 ... Absolute position detection sensor, 3 ... Relative position detection sensor, 4 ... Signal processing part, 4A ... Differential amplifier, 4B ... Amplifier, 5 ... CPU, 5A ... A / D conversion part, 10 ... Object to be measured, 11 ... moving unit, 11A ... shielding scale, 12 ... drive shaft, 12A ... drive shaft pulley, 13 ... motor, 13A ... motor side pulley, 14 ... motor driver, 15 ... turntable, 16, 17 ... photo Interruptor, Sa ... Absolute position detection signal, Sr ... Relative position detection signal, Sd ... Compound position detection signal, Lp, Lph ... Detection level

Claims (6)

An absolute position detection sensor that outputs as a change in the level of the output signal that the device under test has moved to a predetermined position;
A relative position detection sensor that outputs the amount of movement of the object to be measured by the number of pulses of the output signal;
A signal processing unit that generates one output signal as a composite position detection signal from an absolute position detection signal that is an output signal of the absolute position detection sensor and a relative position detection signal that is an output signal of the relative position detection sensor; Have
A position detection device that detects a relative distance from the predetermined position of the object to be measured by measuring the number of pulses of the composite position detection signal based on a position where the composite position detection signal has changed to a level equal to or higher than a predetermined level. . An absolute position detection sensor that outputs as a change in the level of the output signal that the device under test has moved to a predetermined position;
A relative position detection sensor that outputs the amount of movement of the object to be measured by the number of pulses of the output signal;
A signal processing unit that generates one output signal as a composite position detection signal from an absolute position detection signal that is an output signal of the absolute position detection sensor and a relative position detection signal that is an output signal of the relative position detection sensor; Have
By measuring the number of pulses of the composite position detection signal based on the position at which the peak level, the bottom level of the composite position detection signal or a change in a predetermined level specified by the peak level and the bottom level is detected, as a base point. A position detection device that detects a relative distance of the measurement object from the predetermined position. The composite position detection signal is an analog signal,
An A / D converter for A / D converting the composite position detection signal;
The position detection device according to claim 1, wherein a relative distance of the object to be measured from the predetermined position is detected based on the digital signal converted by the A / D conversion unit. The position detection according to claim 1, wherein the signal processing unit generates the composite position detection signal that is the one signal by performing differential amplification processing on the relative position detection signal and the absolute position detection signal. apparatus. The signal processing unit generates the composite position detection signal, which is the one signal, by using the relative position detection signal as a carrier wave and performing amplitude modulation of the carrier wave by the absolute position detection signal. The position detection device described. The dynamic range of the composite position detection signal is X (V),
The amplitude range of the absolute position detection signal is A (V),
The amplitude range of the relative position detection signal is B (V),
When the noise level of the relative position detection signal is Wn (V),
The following (1) and (2) are satisfied.
(1) X> A + B
(2) A> B + Wn
The position detection device according to claim 1.

Images