JPH05306908A - Speckle length measuring gauge - Google Patents

Abstract

PURPOSE:To obtain a speckle length measuring gauge which measures the moving amount of an object by utilizing a speckle pattern caused by diffuse- reflected light from the surface of the object irradiated with a laser light. CONSTITUTION:The gauge calculates the cross-correlation function between a speckle pattern obtained when an object to be measured is at a reference position and another speckle pattern obtained when the object is moved to another position and calculates the moving distance of the object based on the peak position of the cross-correlation function and a microcomputer 7 detects the point of time when the correlation coefficient becomes lower than a prescribed value and, when the coefficient becomes lower than the prescribed value, the reference data which are used as a basis for calculating the cross- correlation function is switched to the current data. The microcomputer 7 discriminates measurement stability from the switching frequency of the reference data and, at the same time, sets a mode in accordance with the operation of a mode selection switch 70. When the measurement stability declines in a first mode, the computer 7 stops the measurement by issuing an alarm, but, when the measurement stability declines in a second mode, continues the measurement by issuing an alarm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speckle length measuring instrument for measuring an amount of movement of an object by utilizing a speckle pattern generated by diffuse reflection light from the surface of the object irradiated with laser light.

[0002]

2. Description of the Related Art Conventionally, a target object is irradiated with a laser beam emitted from a semiconductor laser, a speckle pattern generated by diffused light from the surface of the object is detected, and a speckle pattern associated with movement or deformation of the object is detected. 2. Description of the Related Art A speckle length measuring device that measures a movement amount, a deformation amount, etc. of an object based on a change is known.

As shown in FIG. 11, a measuring head (1) of a speckle length measuring device includes a semiconductor laser (11) and a semiconductor laser (11) in a closed casing having a window (10) for beam emission and light reception. ) Collimator lens (12) that shapes the laser light from the laser beam into a parallel laser beam (17).
One-dimensional image sensor consisting of CCD that photoelectrically converts speckle pattern formed by diffuse reflection at (18)
(13) is arranged.

FIG. 10 shows an example of the construction of a measuring circuit which is connected to the measuring head (1) and calculates the amount of movement of an object based on the image signal from the one-dimensional image sensor (13) and displays it. (Japanese Patent Laid-Open No. 4-50708).

As is well known, the one-dimensional image sensor (13) has a reset signal sent from a buffer amplifier (14),
Scanning in the CCD array direction is repeated at a constant cycle by the start signal and the shift signal. The output signal of the sensor (13) is sent to the sample hold circuit (2) via the first stage amplifier (15).
To eliminate the CCD-specific noise.

The output signal of the sample hold circuit (2) is sent to the binarization circuit (4) via the gain control amplifier (3) and
Valued. Further, the binarized data D is a cross correlation circuit (5)
Is sent to the target object and the cross-correlation function of the speckle pattern at the reference position of the target object and the speckle pattern at the subsequent moving position is repeatedly calculated by shifting the reference position in a timely manner. It is sent to (7).

The microcomputer (7) calculates the moving distance of the object based on the peak position of the cross-correlation function sent from the cross-correlation circuit (5). At this time, the microcomputer (7) detects the time when the cross-correlation coefficient of both speckle patterns falls below a predetermined value, and switches the reference data, which is the basis of the cross-correlation function calculation, to the current data when the cross-correlation coefficient falls below a predetermined value. A control signal S for generating is generated and sent to the cross-correlation circuit (5). Corresponding to this, cross-correlation circuit (5)
The switching of the reference data in is performed.

Further, a reset input signal Res is connected to the microcomputer (7), and when the reset input signal Res rises, the integrated value of the object moving distance is reset, and the reset input signal Res falls from the falling edge of the object. Restart the calculation of the moving distance. As a result, the reset signal Res
The object moving distance in the period from the falling edge of to the rising edge of the next reset signal Res is digitally displayed on the data display (8).

The buffer amplifier (14), sample-hold circuit (2), binarization circuit (4) and cross-correlation circuit (5).
The respective operations are controlled by the timing signals supplied from the timing signal generator (6).

In the above speckle length measuring device, before the cross-correlation function between the reference data and the current data decreases to such an extent that the measurement accuracy is affected as the moving distance increases,
The reference data is switched, and thereafter, the length measurement is continued based on the new reference data, and this is repeated.

Therefore, the moving distance of the object is calculated as an integrated value of the minute moving amounts which can obtain a high correlation, and extremely high accuracy can be obtained even in measuring the long moving distance.

[0012]

By the way, in the measurement by the speckle length measuring instrument, when the light quantity of the laser beam received by the measuring head is too large or too small, or when the target object is abnormally vibrating. In such cases, the measurement state becomes unstable and sufficient measurement accuracy cannot be obtained.

However, in the conventional speckle length measuring instrument, it is not possible to grasp the situation where the measurement state is unstable as described above, and there is a possibility that the measurement is continued with the accuracy lowered. ..

Therefore, the applicant has proposed a speckle length measuring device capable of monitoring whether or not the measurement state is stable.
(Japanese Patent Application No. 4-95334).

In the speckle length measuring device, when the frequency of switching the reference data exceeds the reference value,
It is judged that the measurement state has fallen into an unstable state, and the measurement operation is forcibly stopped at that point.

Therefore, for example, in the case of measuring the entire length of a long object, the measurement stability is temporarily reduced and the measurement operation is stopped even if a minute defect is present on a part of the surface thereof. become.

However, depending on the purpose of measurement, a slight decrease in measurement accuracy does not pose a problem, and it is sometimes desirable to continue the measurement regardless of the decrease in measurement stability.

An object of the present invention is to provide a speckle measurement mode in which, depending on the purpose of measurement, a mode in which the measurement is stopped when the measurement stability decreases and a mode in which the measurement is continued regardless of the decrease in measurement stability can be set. It is to provide a grand total.

[0019]

A speckle length measuring instrument according to the present invention comprises a laser generator for emitting a laser beam toward the surface of a moving target object, and an observation facing the laser irradiation surface of the target object. An image sensor (13) for converting the speckle pattern appearing on the surface into an image signal, and a reference corresponding to the speckle pattern at the reference position of the target object based on the image signal output from the image sensor (13). The degree of approximation between the data and the current data according to the speckle pattern at the moving position thereafter,
The phase difference between both data is calculated as a parameter, and the moving distance of the object is calculated based on the peak position of the distribution of the approximation data (C ₁ , C ₂ , ... Cn) obtained by this.

The characteristic configuration of the first speckle length measuring instrument according to the present invention is that the approximation degree data (C ₁ , C ₂ , ...
Cn), a time when the degree of approximation falls below a predetermined value is detected, and when it falls, the control means for switching the reference data to be the basis of the approximation calculation to the current data, and the number of times the reference data is switched by the control means. And an arithmetic processing means for calculating the measurement stability based on the moving distance of the object, and when the calculated measurement stability shows an unstable value than a predetermined reference stability, a warning is issued and the measurement is stopped. The first mode to
When the calculated measurement stability shows an unstable value than the predetermined reference stability, a warning is issued and the measurement is continued.
And mode selection means for selectively setting the mode.

The characteristic construction of the second speckle length measuring instrument according to the present invention is that the approximation degree data (C ₁ , C ₂ , ... Cn).
On the basis of the above, the control unit detects the time when the degree of approximation falls below a predetermined value, and switches the reference data, which is the basis for the calculation of the degree of approximation, to the current data when the degree falls, and the number of times the reference data is switched by the control unit and the object. Arithmetic processing means for calculating the measurement stability based on the moving distance of the first measurement means, and when the calculated measurement stability shows an unstable value than a predetermined reference stability, a warning is issued and the measurement is stopped. When the mode and the measured stability show an unstable value than the predetermined reference stability, a warning is issued and the object movement distance at that time is
And a mode selection unit for selecting a second mode in which the calculated measurement stability is held for a period until it shows a value more stable than a predetermined reference stability, and the measurement is continued after the lapse of the period. That is what you are doing.

[0022]

When the reference data is switched with the movement of the target object, the moving distance of the target object with one switching is:
In a stable measurement state, the value is substantially constant (for example, 0.2 mm).

However, when the measurement state becomes unstable,
That is, when the light quantity of the laser beam received by the measuring head is too large or too small, or when abnormal vibration occurs in the target object, the target object moves by a small distance smaller than the constant value. Only by doing so, the correlation decreases and the reference data is frequently switched.

Therefore, the ratio between the number of times the reference data is switched and the moving distance of the object represents the stability of the measurement. For example, the moving distance with one reference data switching is 0.2 m.
When the value is much lower than m, it can be determined that the measurement is in an unstable state.

In the first speckle length measuring instrument, when the second mode is selected, even when the calculated measurement stability shows an unstable value than the predetermined reference stability, the normal measurement operation is performed. Is continued, and the measurement result will include some error. However, the existence of the error can be recognized by the warning issued at this time.

In the second speckle length measuring instrument, when the second mode is selected, the object movement distance is changed only during the period when the measurement stability shows an unstable value than the predetermined reference stability. After being held, the normal measurement operation is continued after the lapse of the period. Therefore, the measurement result includes the length of the defect on the object surface as an error. However, the existence of the error can be recognized by the warning issued at this time.

[0027]

According to the speckle length measuring instrument of the present invention, when a slight measurement error is not a problem, the mode can be switched to continue the measurement regardless of the measurement stability.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the present invention is applied to the speckle length measuring instrument shown in FIG. 7 will be described below in detail with reference to the drawings.

FIG. 1 shows the entire structure of the speckle length measuring instrument, in which the measuring head (1), the binarization circuit (4) and the cross-correlation circuit (5) have the same structure as the conventional one.

As shown in FIG. 2, the cross-correlation circuit (5) is provided with a correlator (54) for calculating a cross-correlation function, and a circuit for creating data which is the basis of the cross-correlation function calculation by the correlator (54). Are 256-bit first and second shift registers (51) and (52) arranged in series with each other, and both shift registers (5
1) A data selector (53) interposed between (52).

Binarized data D from the binarization circuit (4)
Through the first shift register (51) to the data selector (5
3) Connected to one input end a. The data selector (5
The output terminal of 3) is connected to the correlator (54) and the input terminal of the second shift register (52). The second shift register (52)
Is connected to the other input terminal b of the data selector (53).

Therefore, by switching the data selector (53) to the terminal a side, the data in the first shift register (51) can be supplied to the correlator (54) via the data selector (53), and at the same time the data selector ( By switching 53) to the terminal b side, the data in the second shift register (52) can be supplied to the correlator (54) via the data selector (53).

Data selector (53) of the cross-correlation circuit (5)
The switching is controlled by the control signal S supplied from the microcomputer (7) as shown in FIG.

The control signal S is a switching number calculation circuit.
It is connected to (9), and the number of times the reference data is switched per unit time is calculated by this.

The microcomputer (7) includes a measurement value calculation unit (71) for calculating the amount of movement of the object based on the peak position of the cross-correlation function, and movement of the object based on the output data of the calculation unit (71). A speed calculation unit (72) for calculating the speed and the calculation unit
(72) and a measurement stability calculation unit (73) for calculating the measurement stability based on the output data of the switching number calculation circuit (9).

Here, when the distribution of the cross-correlation function indicates that the correlation is low, the measurement value calculation unit (71) sends a switching control signal to the data selector (53) of the cross-correlation circuit (5). , The reference data to be supplied to the correlator (54) is switched.

The measurement stability to be calculated by the measurement stability calculation unit (73) is a value obtained by dividing the number of times reference data is switched per unit time by the object moving speed (object moving distance per unit time), that is, the object. The number of times of switching per unit moving distance, or the value obtained by dividing the number of times of switching by the standard number of times of switching can be adopted. In this case, it can be said that the higher the level of measurement stability, the lower the measurement accuracy.

When the calculated measurement stability is an unstable value than a predetermined reference stability, an alarm signal AL is generated and output to the alarm display (82) in FIG. It is output to the value calculator (71).

A reset input signal Res is connected to the microcomputer (7), the integrated value of the object moving distance is reset at the rising of the reset input signal Res, and the calculation of the object moving distance is restarted at the falling. To do. Furthermore, the microcomputer (7) has a mode selection switch (70).
Is connected, and by the switching operation of the switch,
It is possible to select and set the normal mode and the alarm ignore mode, which will be described later.

FIGS. 6A to 6D show the first and second parts shown in FIG.
The operation of the shift registers (51) and (52) and the data selector (53) is shown. At the start of measurement, the data selector (5
3) is set on the "a" side, that is, on the first shift register (51) side. In this state, first, the 256-bit binary data D ₁ corresponding to the speckle pattern at the measurement start point is supplied in parallel to the correlator (54) and the first shift register (51). The correlator (54) receives the data D ₁ from the binarization circuit (4).
And a cross-correlation function with the data transmitted from the first shift register (51) through the data selector (53) is calculated. At the start of measurement, meaningless data is stored in the first shift register (51).
(7) ignores the calculation result of the correlator (54) at this time.

The data D ₂ sent from the binarization circuit in the next cycle is the same as the correlator (54) and the first shift register.
The data D ₁ in the first shift register (51) is sent to the second shift register (52) at the same time as it is sent to the (51) and the correlator (54) causes the binarization circuit ( Current data D ₂ from 4) and the data selector from the first shift register (51)
The cross-correlation function with the data D ₁ output via (53) is calculated and sent to the microcomputer (7). Since both data D ₂ and D ₁ are binary data, the cross-correlation function between them is obtained as a discrete distribution composed of a plurality of correlation value data (C ₁ , C ₂ , ... Cn).

Next, the data selector 53 is switched to the "b" side, that is, the second shift register 52 side by the control of the microcomputer 7. Therefore, the data output from the second shift register (52) is input to the second shift register again via the data selector (53), and the data D ₁ circulates in the second shift register (52). After switching to the terminal b of the data selector (53), the data D3 sent from the binarization circuit is sent to the correlator (54) and the first shift register (51). The correlator (54) calculates a cross-correlation function between the current data D ₃ and the reference data D ₁ and supplies the result to the microcomputer (7).

After that, the same operation is continued. During this process, the microcomputer (7)
The peak position is searched from the set of (C ₁ , C ₂ , ... Cn),
And the correlation value data Cp of the peak position, one pitch of the binary data to the positive side and negative side of the horizontal axis of the cross-correlation function around the peak position (13 .mu.m) shifted by two correlation values Cp _- Difference between ₁ and Cp ₊₁

[0044]

## EQU1 ## Ca = (Cp-Cp- ₁ ) Cb = (Cp-Cp _{+ 1} ) is calculated, and the total value (Ca + Cb) of these difference data is calculated.
To calculate.

When this total value (Ca + Cb) becomes lower than a predetermined reference value, a switching control signal is sent to the data selector (53), and the data selector (53) as shown in FIG.
Is switched to the "a" side, the data in the first shift register (51) is transferred to the second shift register (52), and the reference data is switched.

After the transfer of the data from the first shift register (51) to the second shift register (52) is completed, the data selector (53) is switched to the "b" side again. As a result, the calculation of the same cross-correlation function as described above is continued using the data Di in the second shift register (52) as reference data. Thereafter, similarly, the data selector (53) is switched by the decrease of the total value (Ca + Cb), and the reference data is updated.

The microcomputer (7) calculates the moving distance for each group of correlation value data (C ₁ , C ₂ , ... Cn) sent from the correlator (54) corresponding to one speckle pattern. Perform the procedure for.

That is, first, a group of correlation value data (C ₁ , C ₂ , ... Cn) corresponding to one speckle pattern from the correlator.
Is taken in, the peak position Pp is searched from these data, the moving amount R is calculated based on the search result, and the value of this R is added to the integrated value I to calculate the moving distance A. Is stored in the internal memory.

Next, the microcomputer (7) determines whether or not the reset input signal Res has risen. If the result of the determination is NO, the total value of the difference data (Ca
+ Cb) is calculated, the total value is compared with the switching reference value, and if the total value is larger than the reference value, the process returns to the first data fetching process. When the total value falls below the reference value, the data selector (53) is switched as described above to switch the reference data to the current data. Then, after changing the integrated value I of the object movement amount from the start of the length measurement of the target object to the movement distance A at that time, the process returns to the first data acquisition process.

When the rising of the reset input signal is detected, the calculation result of the moving distance at the rising time is reset, and the calculation of the moving distance is restarted at the time when the falling is detected. Then, when the next reset input signal rises, the calculation result of the moving distance A is sent to the display unit (8).

After that, the reference movement distance Ai is set to the current movement distance A.
, And shifts to the judgment procedure for the total value (Ca + Cb).

As a result, the moving distance A is successively displayed on the display (8) as the object moves.

FIGS. 7A and 7B show the reset input signal Res.
The manner in which the amount of change in the object movement distance is calculated is described. The object moving distance stored in the internal memory of the microcomputer after the start of measurement increases with time as shown in FIG. 7 (a).

3 and 4 show the operation of the microcomputer (7). As shown in FIG. 3, first, based on a selection signal from the mode selection switch (70), a normal mode (first mode) or an alarm ignoring mode (second mode) is selected.
Mode) is determined (S1).

In the normal mode, when the calculated measurement stability shows an unstable value than the predetermined reference stability, a warning is issued and the measurement is stopped. On the other hand, in the alarm ignoring mode, when the calculated measurement stability shows an unstable value than the predetermined reference stability, a warning is issued and the measurement is continued.

In the normal mode, after the correlation data is fetched (S2), the above-mentioned measurement stability is checked (S3). If it is stable, the movement amount is calculated (S4) and the result is output. / Is displayed (S5). Then, it is determined whether or not the reset input is present (S6). If there is no reset input, the process returns to step S2 and the measurement is continued. If there is a reset input, the register inside the microcomputer in which the measured value is set is cleared (S7), and then the process returns to step S2 to restart the measurement.

When it is determined that the operation is unstable in step S3, an alarm output is issued (S8). continue,
The presence or absence of a reset input is determined (S9), and if there is a reset input, the measured value is cleared (S10), the alarm output is canceled (S11), and the process returns to step S2 to restart the measurement.

If the alarm disregard mode is selected in step S1, the correlation data is taken in as shown in FIG. 4 (S12), the measurement stability is checked (S13), and if it is unstable, an alarm is output. After (S14) is issued, if it is stable, the movement amount is calculated without issuing an alarm output (S15), and the result is output / displayed (S16). Then, it is judged whether or not there is a reset input (S17), and if there is no reset input, the process returns to step S12 to continue the measurement.

If there is a reset input, the alarm output is canceled (S18), the measured value is cleared (S19), and the process returns to step S12 to restart the measurement.

According to the above procedure, as shown in FIG. 8, when a fine defect is present on the surface of the object to be measured (18), in the alarm ignoring mode, the normal measurement operation is continued even for the defective part. Therefore, the measured value includes some error E. However, since the presence of an error can be recognized by the alarm signal issued at this time, the measurement result can be used when some error does not matter.

FIG. 5 shows a hold mode procedure which can be adopted instead of or selectively in the alarm disregard mode. In the hold mode, when the measurement stability shows an unstable value than the predetermined reference stability, a warning is issued and the object movement distance at that time is calculated, and the calculated measurement stability is the predetermined reference stability. In this mode, the value is held until it shows a more stable value, and the measurement is continued after the lapse of the period.

In the hold mode, after the correlation data is taken in as shown in FIG. 5 (S21), the measurement stability is checked (S22), and if it is stable, the movement amount is calculated.
(S25), the result is output / displayed (S26). On the other hand, when it is judged to be unstable in step S22, an alarm output is issued (S24), the measured value (object moving distance) set in the internal register is held, and the value is output / displayed. (S26)

Thereafter, it is judged whether or not there is a reset input (S2
7) If there is no reset input, return to step S21 and continue the measurement. If there is a reset input, the alarm output is canceled (S28), the measured value is cleared (S29), and the process returns to step S21 to restart the measurement.

In the hold mode, when the target object (18) has a defect as shown in FIG. 9, a period during which the measurement stability shows an unstable value than a predetermined reference stability due to the presence of the defect. Only, the measured value is held, and the normal measurement operation is continued after the lapse of the period. Therefore, the measurement result includes the length of the defect on the object surface as the error E. However, since the presence of an error can be recognized by the alarm signal issued at this time, the measurement result can be used when some error does not matter.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. The configuration of each part of the present invention is not limited to the above embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a speckle length measuring instrument according to the present invention.

FIG. 2 is a block diagram showing a configuration of a cross correlation circuit.

FIG. 3 is a flowchart showing the operation of the microcomputer in the normal mode.

FIG. 4 is a flowchart showing the operation of the microcomputer in the alarm ignore mode.

FIG. 5 is a flowchart showing the operation of the microcomputer in the hold mode.

FIG. 6 is a timing chart illustrating a reference data switching operation.

FIG. 7 is a timing chart showing changes in the moving distance between reset input signals.

FIG. 8 is a diagram illustrating a change in a measured value in an alarm disregard mode.

FIG. 9 is a diagram illustrating changes in measured values in hold mode.

FIG. 10 is a block diagram showing a configuration of a conventional speckle length measuring instrument.

FIG. 11 is a perspective view showing a schematic configuration of a measuring head of a speckle length measuring instrument.

[Explanation of symbols]

 (1) Measuring head (5) Cross-correlation circuit (7) Microcomputer (70) Mode selection switch (9) Switching frequency calculation circuit (8) Data display (82) Alarm display

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Minamino 2-13 Akita-cho, Takatsuki-shi, Osaka Inside Keyence Corporation

Claims (2)

[Claims] 1. A laser generator for emitting a laser beam toward the surface of a moving target object, and an image sensor for converting a speckle pattern appearing on an observation surface facing the laser irradiation surface of the target object into an image signal. (13)
Based on the image signal output from the image sensor (13), the reference data according to the speckle pattern at the reference position of the target object and the current data according to the speckle pattern at the moving position thereafter. A speckle that calculates the degree of approximation using the phase difference between the two data as a parameter and calculates the moving distance of the object based on the peak position of the distribution of the degree data (C ₁ , C ₂ , ... Cn) obtained by this. The length measuring device detects a time point at which the degree of approximation falls below a predetermined value based on the above-mentioned degree-of-approach data (C ₁ , C ₂ , ... Control means for switching to data, arithmetic processing means for calculating measurement stability based on the number of times reference data is switched by the control means and the moving distance of the object, and the calculated measurement safety When degree showed unstable value than a predetermined reference stability, it warned, to stop the measurement first
A mode and mode selection means for issuing a warning and selectively setting a second mode for continuing the measurement when the calculated measurement stability shows an unstable value than a predetermined reference stability. A speckle length measuring device characterized by that. 2. A laser generator for emitting a laser beam toward the surface of a moving target object, and an image sensor for converting a speckle pattern appearing on an observation surface facing the laser irradiation surface of the target object into an image signal. (13)
Based on the image signal output from the image sensor (13), the reference data according to the speckle pattern at the reference position of the target object and the current data according to the speckle pattern at the moving position thereafter. Speckle that calculates the degree of approximation using the phase difference between the two data as a parameter and calculates the moving distance of the object based on the peak position of the distribution of the degree of approximation data (C ₁ , C ₂ , ... Cn) obtained thereby. The length measuring device detects a time point at which the degree of approximation falls below a predetermined value based on the degree-of-approach degree data (C ₁ , C ₂ , ... Control means for switching to data, arithmetic processing means for calculating the measurement stability based on the number of times reference data is switched by the control means and the moving distance of the object, and the calculated measurement safety. When the degree shows an unstable value than the predetermined reference stability, the first mode to issue a warning and stop the measurement, and when the measurement stability shows an unstable value than the predetermined reference stability , A warning is issued, and the object movement distance at that time is held for a period until the calculated measurement stability shows a value more stable than a predetermined reference stability, and measurement is continued after the lapse of the period. A speckle length measuring instrument comprising a mode selecting means for selecting the second mode.