JPH10288538A - Offset adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the precision with a simple circuit by calculating the offset quantity on the basis of the maximum value and minimum value of the other detection signal when the value of either one of offset regulating sine wave signal and cosine wave signals is 0. SOLUTION: Offset regulating sine wave signal sin θ and cosine wave signal cos θ are converted into digital signals by an A/D converter 22, respectively. At this time, offset signal is subtracted in an adding amplifier 21. The digital signals from the converter 22 are transmitted to an inverse trigonometric function part 23, an angle θ is outputted and processed as position data within the sine wave. Namely, two offset regulating signals differed in phase by 90 deg. are detected. When the value of either one of the detected signals is 0, the offset quantity is calculated on the basis of the maximum value and minimum value of the other detected signal, and an offset regulation is performed on the basis of this offset quantity. Since the maximum value and minimum value are thus detected with zero-cross, a comparator circuit or the like is dispensed with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset adjustment method used for positioning various devices.

[0002]

2. Description of the Related Art Conventionally, a transfer device 10 of a device used for manufacturing a semiconductor device as shown in FIG. 4 reads a scale using an optical or magnetic sensor 1 as an encoder for detecting the position of a moving body. This is detected as an electric signal such as a sine wave signal, and the detected analog signal is converted into a digital signal to determine a moving direction, a moving position, and the like.

For example, a carrier 3 in which a wafer as a substrate to be processed is stored and a transfer arm 4 for loading and unloading the wafer are configured to be relatively movable up and down. In order to perform the detection at the same pitch, the position detection is performed by the signal scale 2 and the sensor 1. In such an encoder, a signal as shown in FIG. 2 advances in the direction of the maximum value or the minimum value and the operation is controlled at a zero point indicated by an arrow Y, or a periodic scale signal as shown in FIG. To obtain position information by detection interpolation.

[0004]

However, the signal read from the sensor 1 may include a DC offset voltage O 'as shown in FIG. As a cause of this, it is considered that the accuracy is deteriorated due to the influence of temperature change and aging of the circuit element and the like. Such a shift in the offset voltage greatly affects the accuracy of the absolute position,
In particular, in the transfer apparatus shown in FIG. 4, a slight displacement causes a problem such as breakage of the wafer.

When an analog-to-digital converter is used as the signal detecting means, a converter having more bits than the number of divisions is necessary in consideration of the offset, and the influence of noise is avoided. Therefore, it is necessary to increase the voltage of the converter in order to increase the voltage of one bit, and thus there is a problem in the number of components, power consumption, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a highly accurate offset adjusting method with a simple circuit.

[0007]

In order to solve the above-mentioned problems, there is provided a step of detecting two signals having a phase difference of 90 ° for offset adjustment, and a method of detecting one of the detected signals having a value of 0. And calculating an offset amount based on a maximum value and a minimum value of the other detection signal, and performing an offset adjustment based on the offset amount.

According to such a configuration, since the maximum value and the minimum value are detected by a so-called zero cross, a comparator circuit or the like is not required, and the displacement can be reliably adjusted by a simple circuit.

According to such a configuration, when adjusting the offset with the analog output, it is possible to use the number of bits of the analog-digital converter for the interpolation (division) of the position without considering the offset. it can. Therefore, a desired offset adjustment can be sufficiently performed using an analog-digital converter having a small number of bits. further,
Since the analog-to-digital converter and the digital-to-analog conversion in the one-chip microcomputer are sufficient, the electric circuit and the power supply circuit are simplified.

[0010] In the present invention, two phases having a 90 ° phase difference are used.
Preferably, the two signals are a sine wave signal and a cosine wave signal. In the present invention, the offset amount may be calculated by a digital signal, the digital signal may be converted into an analog signal, and the offset may be adjusted based on the analog signal. The offset adjustment may be performed based on the digital signal.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. First, the sensor 1 in FIG. 4 detects two signals having different phases with respect to the angle θ depending on the intensity of light, for example, a sine wave signal (SINθ) and a cosine wave signal (COSθ). Then, this detection signal is input to the offset adjustment circuit 20 shown in FIG.

FIG. 5 is a block diagram for explaining an offset adjusting method according to an embodiment of the present invention. The addition amplifier 21 subtracts the obtained offset adjustment signal, and the analog-digital converter 22 outputs a sine wave signal (SINθ) from the sensor and a cosine wave signal (COSθ).
Is converted into a digital signal.

The inverse trigonometric function section 23 outputs an angle θ based on the sine wave signal and the cosine wave signal, and processes the position data in the sine wave. The determination unit 24 is a unit that determines which of a sine wave signal and a cosine wave signal is latched based on which signal is 0. The latch unit 25 latches the signal determined by the determination unit 24.

The selection section 26 determines whether the signal latched by the latch section 25 is the maximum value or the minimum value based on the polarity of the signal. The selection section 26 includes a maximum value latch section 27 and a minimum value latch. The unit 28 latches the maximum value signal or the minimum value signal according to the result of the determination by the selection unit 26. Further, the buffer unit 34
The signal transfer is delayed more than the signal of the selecting unit 26.

The first adder 29 includes a maximum value latch 27
And the offset adjustment amount is obtained based on the respective signals latched by the minimum value latch unit 28. Also,
The second adding unit 30 adds the signal of the offset adjustment amount obtained by the first adding unit 29 and the previous offset adjustment amount latched by the latch unit 31.

The digital-analog converter 32 converts the offset adjustment signal added by the second adder 30 into an analog signal, and the amplifier circuit 33 adjusts the output of the offset adjustment signal.

In the above-mentioned circuits, a circuit for latching a signal at the rising edge is used for the latch unit 25 and the latch unit 31, and the gate of the maximum value latch unit 27 and the minimum value latch unit 28 has the L level. Sometimes a circuit that latches signals is used.

A method of performing the offset adjustment according to the present invention using the circuit having the above configuration will be described. Here,
The case where the cosine wave signal is 0 will be described. First, 90 °
The two signals having different phases, that is, the sine wave signal and the cosine wave signal, are respectively converted into digital signals by the analog-digital converter 22. At this time, the obtained offset adjustment signal is subtracted in the addition amplifier unit 21.
The digital signals from the converter 22 are respectively SIN
are sent to the inverse trigonometric function unit 23 as θ and COS θ, and the angle θ is output and processed as position data in a sine wave.

Here, when one value of the digital signal from the converter 22 is 0, here, when the cosine wave signal is 0, the judgment section 24 goes to the H level, and the value of SINθ is latched by the latch section 25. Latch. Here, when θ = 0, S
Since INθ = θ, θ = 90 °, 27
At 0 °, θ is determined by the value of COS θ, and since the value hardly changes near the maximum value / minimum value, the COS θ is similar to the error due to the interpolation number of the sine wave.
Can be excluded from the input of the determination unit 24.

Next, the signal latched by the latch section 25 is sent to the select section 26, where the select section 26
It is determined whether the signal of SINθ is the maximum value or the minimum value based on the polarity of the signal. Then, based on the determination result, the maximum value latch unit 27 or the minimum value latch unit 2
8 to open the gate and latch the signal. Here, the signal transfer in the buffer section 34 is delayed more than the signal transfer in the select section 26.

Next, the respective signals latched by the maximum value latch unit 27 and the minimum value latch unit 28 are subjected to an offset adjustment amount by a first addition unit 29, and the signal of the offset adjustment amount is added to a second addition value. The previous offset adjustment amount sent to the unit 30 and latched by the latch unit 31 in the second adding unit 30 is added to the current offset adjustment amount.

Thereafter, the offset adjustment signal added by the second adder 30 is converted into an analog signal by the digital-analog converter 32 and output as an offset adjustment signal. Thereafter, the output of the offset adjustment signal is halved by the amplifier circuit 33. The offset adjustment signal is sent to the addition amplifier 21. In this way,
Offset adjustment is performed. Note that the amplifier circuit 33 may be unnecessary by inputting a signal to the digital-analog converter 32 after shifting it by one bit.

In the above embodiment, the cosine wave signal is 0
However, the present invention can be applied to a case where the sine wave signal is zero. Further, in the above-described embodiment, the case where two signals having a 90 ° phase difference are a sine wave signal and a cosine wave signal has been described. Similar effects can be obtained.

In the above embodiment, the case has been described where the offset amount is calculated by a digital signal, the digital signal is converted to an analog signal, and the offset is adjusted based on the analog signal.
The present invention can also be applied to a case where an offset amount is calculated using a digital signal and offset adjustment is performed based on the digital signal.

[0025]

As described above, according to the offset adjusting method of the present invention, since the maximum value and the minimum value are detected at the zero cross point, the offset can be accurately adjusted without a change in position.

[Brief description of the drawings]

FIG. 1 is a diagram showing a positioning sensor signal.

FIG. 2 is a diagram showing a scale signal.

FIG. 3 is a diagram showing an offset.

FIG. 4 is a schematic diagram of a transfer device to be subjected to offset adjustment.

FIG. 5 is a block diagram illustrating an offset adjustment method according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sensor, 2 ... Scale, 3 ... Carrier, 4 ... Carrier arm, 20 ... Offset adjustment circuit, 21 ... Addition amplifier part, 22 ... Analog-digital conversion part, 23 ... Inverse trigonometric function operation part, 24 ... Judgment part, 25 latch unit, 26 selection unit, 27 maximum value latch unit, 28 minimum value latch unit, 2
9: first addition unit, 30: second addition unit, 31: latch unit, 32: digital-analog conversion unit, 33: amplifier unit, 34: buffer unit, Y: arrow, O ': offset.

Claims (4)

[Claims] 1. A step of detecting two signals having a phase difference of 90 ° for offset adjustment, and when one of the detected signals has a value of 0, a maximum value and a minimum value of the other detected signal are set to An offset adjustment method comprising: calculating an offset amount based on the offset amount; and performing an offset adjustment based on the offset amount. 2. The method according to claim 1, wherein the two signals having a 90 ° phase difference are a sine wave signal and a cosine wave signal. 3. The method according to claim 1, wherein the offset amount is calculated by a digital signal, and the digital signal is converted into an analog signal.
3. The offset adjustment method according to claim 1, wherein offset adjustment is performed based on the analog signal. 4. The offset adjustment method according to claim 1, wherein the offset amount is calculated by a digital signal, and the offset adjustment is performed based on the digital signal.