JPH01131415A - Optical displacement measuring instrument - Google Patents

Abstract

PURPOSE:To obtain the optical displacement measuring instrument of simple constitution which can be manufactured at low cost by providing an absolute value arithmetic means which calculates the absolute values of 1st and 2nd outputs, a ROM stored with data on arctangent pi/2, etc. CONSTITUTION:This instrument consists of absolute value computing elements 10 and 11 which calculate the absolute values of the outputs a1 and a2 of AD converters 91 and 92, the ROM 14 stored with data on arctangent pi/2, a data selector 13 which switches the output of the computing element 10 according to the signs of the outputs a1 and a2 and inputs it to the ROM 14, etc. The absolute values of the two outputs are calculated 10 and 11, the outputs of the computing elements 10 and 11 are switched 13 according to the signs of those outputs and inputted to the ROM 14, and a corrector 12 calculates a correction output from the signs of those outputs. Consequently, the ROM 14 is stored with only the data on arctangent over pi/2, input data is rearranged according to the most significant digit bit of data for finding the arctangent, and a correcting value is calculated from the most significant digit bit and added. The capacity of the ROM is reducible to 1/4.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention is directed to the improvement of an optical displacement measuring device that uses light to measure minute mechanical displacements in a non-contact manner.

<Prior art> The applicant has disclosed in Japanese Patent Application No. 61-305847 that high-speed,
We proposed an optical displacement measuring device that can achieve high resolution. This proposal will be explained below based on FIG. In FIG. 6, a striped pattern 2 is formed on the surface of the measurement object l. The image of this pattern 2 is transmitted to an image sensor 4 via a lens 3.
is imaged.

The image sensor 4 has photodiodes 5 arranged one-dimensionally, and converts the intensity of imaged light into a current signal. The current signal of the photodiode 5 is converted into a voltage signal by a current-voltage converter 6, and is input to the calculation means 7.8. The calculation means 7 includes a multiplier 71 and an adder 72.
is included. The output of the current-voltage converter 6 is multiplied by a coefficient S in a multiplier 71. The subscript i represents the order counted from the end of the photodiode 5, and S-=sin (2yrk i/m) = (1)m
: The number of photodiodes 5: An arbitrary number satisfying 1≦5 m/2. The output of the fifth photodiode 5 from the end has a coefficient S
j is multiplied. The outputs of the multiplier 71 are added by an adder 72. That is, the output ■1 of the adder 72 is ■1 = α (ΣV IS i ) = α (Σ v, 5in (2π ki/m n )...
(2) Output α of the first photodiode 5 from V-:l becomes a constant.The calculation means 8, like the calculation means 7, has a multiplier 81 and an adder 82. It is configured. The operation is almost the same as that of the calculation means 7, but the coefficient c multiplied by the multiplier 81 is C-=cos (2πki/m), and the meanings of the variables k, 1, and m are the same as in equation (1). It is. Therefore, the output V2 of the adder 82 is V2=α(Σvi
Ci ) =α(Σ%J CO3(2πk i 7m) 1. ■9. The meaning of α is the same as in equation (2).

This ■ and v2 are input to the calculation means 9. Arithmetic means 9
g, tAD converters 91 and 92, and ROM 93. V and V2 are respectively AD converters 91.
It is converted into a digital signal at 92 and applied to the address of ROM 93. In the ROM 93, the value of θ calculated by the following equation (3) is stored in the data area corresponding to the address.

θ=tan (V/V2>・・・・・・・・・
(3) Therefore, the value of θ is obtained as the output of the calculation means 9. This θ is the phase of the Fourier transform coefficient of the second harmonic of the pattern whose fundamental wavelength is the length of the image sensor 4, and from this value, the position of the pattern, that is, the displacement of the object to be measured 1 can be known.

<Problem to be solved by the invention> However, in such an optical displacement measuring device, the phase θ to be measured spans a wide range from 0 to 2π, so the ROM 93 must cover this range. However, this has the drawback that the capacity of the ROM increases, making the configuration complex and expensive.

<Object of the Invention> An object of the present invention is to provide an optical displacement measuring device that has a simple configuration and can be made at low cost.

Means for Solving the Problems> In order to solve the above problems, the present invention includes a method in which a striped pattern provided on an object whose displacement is to be measured is received by a plurality of light receiving elements arranged in a one-dimensional manner. From the arctangent of the ratio of the output of this light-receiving element multiplied by a multiplication factor that varies sinusoidally with respect to the position of the light-receiving element and the sum of the output multiplied by a multiplication factor that varies cosine-waveformly, In the optical displacement measuring device for determining the displacement of the object to be measured, the absolute values of the two outputs are calculated by an absolute value calculator, and the output of the absolute value calculator is switched depending on the sign of these outputs to calculate π/ Two minutes of data is input to a ROM that stores the data, and a correction output is calculated from the sign of these outputs.

Furthermore, these outputs are time-divisionally input to a single absolute value calculator to calculate their absolute values, and the calculated absolute values are latched in the first and second latches.

The latch controller determines which latch to latch on based on the signs of the first and second outputs. The values latched in the first and second latches are input to a ROM in which arctangent data for π/2 is stored. Further, the output of this ROM is corrected by a corrector that calculates a correction output from the signs of the first output and the second output.

<Example> FIG. 1 shows an example of the optical displacement measuring device according to the present invention, and the same reference numerals as in FIG.
The explanation will be omitted. In FIG. 1, reference numeral 10 denotes an absolute value calculator, into which the output of the AD converter 91 including the MSB is input, and calculates and outputs the absolute value of this output. Reference numeral 11 denotes an absolute value calculator, into which the output of the AD converter 92 including the MSB is input, and calculates and outputs the absolute value of this output. It is assumed that the outputs of the AD converters 91 and 92 are expressed in one's complement. 12 is a corrector, and AD converter 9
The most significant bit MSB of the output of 1.92 is input. 1
3 is a data selector, into which the output of the absolute value calculator 10.11 is input. The most significant bit MSB of these outputs is input as a control signal. 14 is R
OM, and the output of the data selector 13 is input to that address. 15 is a buffer, into which the outputs of the ROM 14 and the corrector 12 are input. The output of the corrector 12 is made to be higher than the output of the ROM 14.

Next, the operation of this embodiment will be explained. AD converter 91.
It is assumed that the output of 92 is, for example, 8 bits and is encoded in one's complement format. That is, when the most significant bit is 0, it represents a positive number, and when it is 1, it represents a negative number. This A
The outputs of the D converters 91 and 92 are input to an absolute value calculator 10 and 11 to calculate their absolute values. The output of the absolute value calculator 10.11 is 7 bits. This output is input to the data selector 13. The data selector 13 is composed of two switches 131 and 132. The output of the absolute value calculator 10 is input to the contact A of the switches 131 and 132, and the output of the absolute value calculator 11 is input to the contact B of the switches 131 and 132. Common contact C of switches 131 and 132 is ROM14
is connected to the address of Switches 131 and 132 are A
It is driven by the most significant bit MSB of the output of D converters 91 and 92. That is, when the MSBs of both AD converters 91 and 92 are the same, the common contact C of the switch 131 becomes the contact A,
Common contact C of switch 132 is connected to contact B. Therefore, the output of the absolute value calculator 10 is input to the Y of the ROM 14, and the output of the absolute value calculator 11 is input to the X of the ROM 14.

When the MSBs of the AD converters 91 and 92 are different, that is, when one is 1 and the other is O, the common contact C of the switch 131 is connected to the contact B, and the common contact C of the switch 132 is connected to the contact A. . Therefore, the output of the absolute value calculator 10 is stored in the ROM 14, and the output of the absolute value calculator 11 is stored in the ROM 14.
It is input to Y of 14. The ROM 14 stores θ in the range from 0 to π/2 expressed by equation (4) such that π/2 is the full scale.

θ=↑an” (Y/X) =・---(4)
On the other hand, the corrector 12 generates a 2-bit signal as follows from the MSB of the input AD converters 91 and 92.

■When the MSBs of the outputs of AD converters 91 and 92 are both 0...0 ■When the MSBs of the outputs of AD converters 91 and 92 are O, and the AD converters 92
When the MSB of the output is 1......1■AD
When the MSB of the output of converters 91 and 92 is 1...
...2 ■If the MSB of the output of the AD converter 91 is 1, the AD converter 92
When the MSB of the output of 3 is 0, the buffer 15 combines the outputs of the ROM 14 and the corrector 12 and outputs the result. Figure 2 shows this situation. In Figure 2, X,
Y represents X and Y input to the ROM 14, respectively;
The right side and the top side are positive. θ1 in the first quadrant is X,
Since both Y are positive, the output of the corrector 12 becomes 0, and the value of θ1 is obtained in the buffer 15. θ2 in the second quadrant
is considered as θ2=π/2+952, the corrector 12 outputs π/2, and the data selector 13 outputs absolute value calculators 10 and 11 to obtain T2.
Replace. Considering θ3 in the third quadrant as θ3=π+T3, the corrector 12 outputs π. θ in the fourth quadrant
4 is considered as θ4=3π/2 + F 4 , and the corrector 12 outputs 3π/2, and the data selector 13 switches the outputs of the absolute value calculators 10 and 11 to obtain P4. For this purpose, the data stored in the ROM 14 is set so that π/2 becomes the full scale. The output of the AD converters 91 and 92 is the absolute value calculator 1.
Since the absolute value is calculated at 0.11, the same ROM
γ2 to T4 can be found by

Figure 3 shows an example of the configuration of the absolute value calculator.
) is an example using an EXOR gate.

One input of the EXOR gate 16 is connected to an AD converter 91.
The lower 7 bits of 92 are input, and the most significant bit MSB is input to the other input. When MSB is 0, EXO
The output of R gate 16 will be the same as one input, and the MSB
When is 1, it is inverted and the absolute value is determined. (B) is an example using a 3-state buffer of inversion and non-inversion. A
The lower 7 bits of D converters 91 and 92 are non-inverting buffer 1.
7 and an inversion buffer 18. In addition, an AD converter 91 is connected to the control terminal OE of the non-inverting buffer 17.
．． 92 most significant bits MSB of inverting buffer 18
A signal obtained by inverting the MSB by the inverter 19 is input to E. When 0M5B is O or positive, the non-inverting buffer becomes active, so the lower 7 bits are output as is, and when the MSB is 1, the inverting buffer 18 is active. becomes and is reversed. In this way, the absolute value is determined.

FIG. 4 shows another embodiment. Note that the same elements as in FIG. 1 are given the same reference numerals and their explanations will be omitted. In Figure 4,
20 is an absolute value calculator which alternately inputs the outputs of the AD converters 91 and 92 including the MSB, calculates their absolute values, and outputs them. Numerals 21 and 22 are latches, into which the output of the absolute value calculator 20 is input and latched. Reference numeral 23 denotes a latch controller, into which MS and B, which are the signs of the outputs of the AD converters 91.92, are input, and the output thereof is input to the latch controller 21.23.
22.

Next, the operation of this embodiment will be explained based on FIG.

In FIG. 5, (A) is the output of the absolute value calculator 20, and the absolute values of the AD converters 91 and 92 are alternately output. 1.2 indicate the absolute values of the outputs of the AD converters 91 and 92, respectively.The configuration of the calculation section of the absolute value calculation unit 20 is the same as that explained in FIG. 3, for example. (B) and (C) are the MSBs or sign bits of the outputs of the AD converters 91 and 92, respectively, where a low level represents positive and a high level represents negative. (D) is a latch controller input to the latch 22. 23, (E) represents the output of the latch controller 23 that is input to the latch 21. The latches 21 and 22 latch the output of the absolute value calculator 20 at the rising edge of these signals. Signals (D) and (E) are output whenever the absolute value calculator 20 outputs the absolute value of the output of the AD converter 91, and the values are latched in the latches 21 and 22.

When outputting the absolute value of the output of the AD converter 92, (
If the signs of the outputs of the AD converters 91 and 92 represented by B) and (C) are the same, a signal <D) is output, and the absolute value of the output of the AD converter 92 is latched in the latch 22, and the sign becomes If they are different, a signal (E) is output and the AD converter 9
The absolute value of the output of 2 is latched into the latch 21. Therefore, when the signs of the outputs of the AD converters 91 and 92 are the same, the absolute value of the output of the AD converters 91 is stored in the latch 21, and the absolute value of the output of the AD converters 91 and 92 is the same.
The absolute value of the output of the AD converter 92 is latched. Moreover, when the signs are different, the results are reversed. As a result, ROM1
Since the same data as in the embodiment shown in FIG. Buffer 15 immediately before outputting the absolute value of
By reading out the output of , the same result as in the embodiment of FIG. 1 can be obtained. In this embodiment, only one absolute value calculator is required and no data selector is required, which simplifies the configuration.Also, since input to the absolute value calculator is time-divided, the number of inputs and outputs is small. This has the advantage that it is easy to form a gate array. Note that the procedure for latching data in the latches 21 and 22 is not limited to the procedure of writing the same data and rewriting it as in this embodiment, and the data may be distributed by the latch controller 23.

In addition, in these embodiments, 1 is used as the AD converter 91.92.
Although the description has been made assuming that an AD converter that outputs the complement of is used, an AD converter that outputs an offset binary code may also be used. In this case, it can be handled similarly by inverting and using the most significant bit.

<Effects of the Invention> As described above in detail based on the embodiments, in this invention, only data from O to π/2 is stored in the ROM, and the input data is determined by the most significant bit of the data for which the arctangent is to be calculated. In addition, the correction value is calculated and synthesized from the most significant bit. Therefore, R
The capacity of OM can be reduced to 1/4.

Furthermore, since the most significant bit of the input data is corrected and the two most significant bits of the output are combined, the data length of the ROM can be shortened, and the capacity of the ROM can be further reduced.

Furthermore, in the configuration shown in FIG. 4, only one absolute value amplifier is required;
Furthermore, since no data selector is required, the configuration becomes even simpler.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an optical displacement measuring device according to the present invention, FIG. 2 is a diagram for explaining the procedure for determining an angle, FIG. 3 is a diagram showing the configuration of an absolute value calculator, FIG. 4 is a block diagram showing an embodiment of the pond, FIG. 5 is a diagram for explaining its operation, and FIG. 6 is a block diagram showing the structure of a conventional optical displacement measuring device. 9192...AD converter, 10, 11.20...Absolute value calculator, 12...Corrector, 13...Data selector, 14...ROM, 15...Buffer, 21,
22... Latch, 23... Latch controller. Figure 2 Figure 3 (A)
(B)/A Figure 5 (E)

Claims (2)

[Claims] (1) Provide a striped pattern on the measurement object whose displacement is to be measured,
This striped pattern is received by a plurality of light-receiving elements arranged one-dimensionally, and the output of the light-receiving element is multiplied by a multiplier that varies sinusoidally with respect to the position of the light-receiving element.
and a second output obtained by multiplying the output of the light-receiving element by a multiplier that changes in a cosine wave shape with respect to the position of the light-receiving element and adding the resulting optical displacement. In the measuring device, an absolute value calculating means for calculating the absolute values of the first output and the second output, a ROM storing data of an arctangent of π/2, and a ROM for calculating the absolute values of the first output and the second output. A data selector that switches the output of the absolute value calculator and inputs it to the ROM based on the sign of the output, and a corrector that calculates a correction output from the sign of the first output and the second output. Optical displacement measuring device. (2) Provide a striped pattern on the measurement object whose displacement is to be measured,
This striped pattern is received by a plurality of light-receiving elements arranged one-dimensionally, and the output of the light-receiving element is multiplied by a multiplier that varies sinusoidally with respect to the position of the light-receiving element.
and a second output obtained by multiplying the output of the light-receiving element by a multiplier that changes in a cosine wave shape with respect to the position of the light-receiving element and adding the resulting optical displacement. The measuring device includes a single absolute value calculator that calculates the absolute values of the first and second outputs in a time-sharing manner, first and second latches, and the first and second outputs of the first and second outputs. Signs are input and the output of the absolute value calculator is determined by the first or second sign.
a latch controller that selects and latches the latch;
a ROM in which the outputs of the first and second latches are input and arctangent data for π/2 is stored; and a corrector that calculates a correction output from the signs of the first and second outputs. An optical displacement measuring device characterized by having: