JP2008032540A - Surface shape measuring apparatus and method for detecting anomaly of stylus load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a stylus and a pickup from being broken due to excessive loads acting on the stylus by detecting anomalies of loads acting the stylus in a surface shape measuring apparatus having the stylus which comes into contact with surfaces of objects to be measured. <P>SOLUTION: The surface shape measuring apparatus 1 for measuring the surface shape of an object to be measured W by relatively moving the stylus 11 as keeping the stylus 11 in contact with a surface of the object to be measured W, detecting displacements of the stylus 11 caused by irregularities of the surface of the object to be measured W, and creating displacement signals, includes a stylus-load-anomaly detection part 62 for detecting anomalies in changes in the displacement signals as anomalies in loads actin on the stylus 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, the stylus is moved relative to the surface of the object to be measured, and at this time, a displacement signal is generated by detecting the displacement of the stylus caused by the undulation of the surface of the object to be measured, The present invention relates to a surface shape measuring apparatus for measuring a shape, and more particularly, to a technique for preventing damage to the stylus or a pickup unit that detects displacement of the stylus.

  The surface shape measuring device moves the stylus and the object to be measured while pressing the stylus against the surface of the object to be measured with a predetermined measurement pressure, and the displacement of the stylus caused by the undulation of the surface of the object to be measured at that time. The amount is converted into an electrical signal, the displacement signal converted into an electrical signal is read by a computer or other computer, and sequentially read at each point on the line segment having the relative movement length of the stylus with respect to the object to be measured. Each displacement amount is arranged to create surface shape data of an object to be measured (for example, Patent Document 1 below). FIG. 1 shows a basic configuration of the surface shape measuring apparatus.

The surface shape measuring apparatus 1 is provided with a table 2 along the XY plane for placing an object to be measured. A column 3 is erected on the table 2. A movable portion 4 is attached to the column 3. The column 3 incorporates a motor (not shown), and the motor can move the movable portion 4 up and down along the column 3 (that is, along the Z direction).
The movable part 4 is provided with a holder 5, an arm part 10 is attached to the holder 5, and a pickup 6 is attached to the tip of the arm part 10. The movable part 4 also incorporates a motor (not shown), and the holder 5 can be driven in the X direction.

A measuring element (pickup) 6 for measuring the surface roughness of the object to be measured placed on the table 2 is provided at the tip of the arm 10, and the pickup 6 has a stylus at one end. A cantilever 7 provided with 11 is attached. FIG. 2 shows the internal structure of the pickup.
The pickup 6 has a fulcrum 21 that supports the cantilever 7 so as to be swingable about a direction perpendicular to the longitudinal direction of the cantilever 7 and the protruding direction of the stylus 11, and urges the cantilever 7 to keep the stylus 11 constant. And an urging means 22 that is an elastic body such as a spring for pressing against the measurement surface 103 of the workpiece W with the measurement pressure.

  While the stylus 11 is pressed against the measurement surface 103, the calculation unit 40 such as a computer that controls the operation of the surface shape measuring apparatus 1 moves the driving unit 4 at a constant speed in the X direction via the moving mechanism driving circuit 50. Move. Then, the stylus 11 is displaced in the direction of the measurement pressure by the urging means 22 according to the undulation of the measurement surface 103 (that is, the displacement is caused in the vertical direction with respect to a predetermined reference surface of the movable portion 4). . The cantilever 7 swings due to the displacement of the stylus 11, and the swing amount is converted into an electric signal by the differential transformer in the pickup 6.

  In the illustrated configuration example, the differential transformer is configured to include an excited primary coil 23, two secondary coils 25, and a magnetic core 26 inserted in the center thereof. It is fixed to the cantilever 7. When the cantilever rotates in accordance with the displacement of the stylus 11, the magnetic core 26 moves in the coil accordingly, and the mutual inductances of the two secondary coils 25 with respect to the primary coil 23 change. For this reason, a difference occurs between the induced voltages of the two secondary coils 25, and an output voltage corresponding to the amount of movement of the core, that is, the amount of displacement of the stylus 11 can be obtained. A differential inductance, a laser interferometer, or an optical encoder may be used instead of the differential transformer.

The output signal of the pickup 6 is input to an analog / digital conversion circuit (ADC) 30. The analog / digital conversion circuit 30 converts the analog signal into a digital displacement signal string at a predetermined sampling period.
A digital displacement signal train is input to the computer 40. The calculator 40 arranges the values of the displacement signals sequentially read while moving the movable part 4 at a constant speed at each point on the line segment having the length of the movable part 4 to move the measured object. Create surface shape data.

JP 2002-107144 A Japanese Patent Laid-Open No. 2005-127934

  In the surface shape measuring apparatus 1 for bringing the stylus 11 into contact with the object to be measured as described above, if there is a hole or a step on the surface of the object to be measured, the stylus 11 is caught there, and an excessive load is applied to the stylus 11. May work. However, since the conventional surface shape measuring apparatus 1 does not have a means for detecting the load acting on the stylus 11, the movable portion 4 and the column 3 continue to be driven with an excessive load acting on the stylus 11, and the stylus 11 may be damaged.

In particular, as shown in FIG. 3A, when measuring the surface shape of the inner surface of the horizontal hole 101 of the workpiece W, when moving the stylus to the measurement start point indicated by the dotted line in the figure, The stylus 11 hits the back of the hole 101 and is easily damaged.
Further, as shown in FIG. 3B, when the hole 102 is present on the surface of the workpiece W, the stylus 11 falls into the hole 102 and may be caught by the stylus 11 to be damaged. .

Further, since the conventional surface shape measuring apparatus 1 does not monitor the output signal of the pickup 6 when the stylus 11 is not being measured, for example, when the stylus 11 is moved to the measurement start point, such an output signal is not monitored. When moving, the stylus 11 hits against an obstacle, and the stylus 11 and the pickup 6 may be damaged.
In view of the above problems, the present invention is a surface shape measuring device having a stylus that contacts the surface of an object to be measured. The purpose is to prevent damage to the stylus and pickup due to excessive load.

In order to achieve the above object, the present invention uses a displacement signal obtained by detecting the displacement of the stylus in order to detect an abnormality in the load acting on the stylus.
When the stylus is moving normally on the measurement surface, the value of the displacement signal for detecting the displacement amount of the stylus remains within a certain range of the fluctuation range and rate of change. On the other hand, when the stylus is caught by irregularities on the measurement surface or when it hits an obstacle, for example, when the load is excessively applied to the stylus, for example, the change of the displacement signal is reduced or, for example, normal A change in size that cannot occur.
Therefore, by detecting such an abnormality in the displacement signal, it is possible to detect a state in which an excessive load is applied to the stylus as in the above example.

  According to the surface shape measuring apparatus according to the first embodiment of the present invention, the displacement is detected by moving the stylus while making contact with the surface of the object to be measured, and detecting the displacement of the stylus caused by the undulation of the surface of the object to be measured. A surface shape measuring device that generates a signal and measures the surface shape of an object to be measured, and includes a stylus load abnormality detection unit that detects an abnormality in a displacement signal as an abnormality in a load acting on the stylus. An apparatus for measuring the surface shape is provided.

  Further, according to the stylus load abnormality detection method according to the second aspect of the present invention, the stylus is moved relative to the surface of the object to be measured while being in contact with the surface of the object to be measured. In the surface shape measurement for measuring the surface shape of the object to be measured by generating a displacement signal in which the displacement is detected, an abnormal change in the displacement signal is detected as an abnormal load acting on the stylus.

When an abnormality in the load acting on the stylus is detected, for example, a moving mechanism that moves the object to be measured and the stylus relatively is stopped. This can prevent damage to the stylus and the sensor that detects the amount of displacement.
In order to detect an abnormal change in the displacement signal, for example, the displacement signal is converted into a frequency domain signal, and when the change in the frequency domain signal exceeds a predetermined allowable range, it is determined that the change in the displacement signal is abnormal. May be.
When the stylus is moving normally on the measurement surface, a frequency component within a predetermined frequency range is generated in the displacement signal according to the moving speed of the stylus and the roughness of the measurement surface, and the frequency domain signal changes. Although it is stable, if an abnormal condition such as that described above occurs, the change in the frequency domain signal will increase, and by detecting such a change in the frequency domain signal, an abnormality in the load acting on the stylus can be detected. It becomes possible to do.

The predetermined allowable range may be defined as an allowable intensity range of a frequency signal component included in the frequency domain signal and lower than a predetermined frequency band. At this time, the predetermined frequency band is the frequency range of the signal that is expected to occur in the frequency domain signal when the stylus and the object to be measured are moved relative to each other while keeping the stylus along the undulation of the surface of the object to be measured. May be defined as
Further, the predetermined change width of the frequency domain signal may be determined as an allowable frequency range of a frequency having a frequency component having the maximum intensity.

  When the stylus is supported by a swingable lever member such as the cantilever shown in FIG. 2 and the displacement signal is generated by detecting the swing amount of the lever member, for example, the stylus is caught on the measurement surface or If an attempt is made to move the stylus while striking an obstacle, the lever member is distorted and the displacement signal detected by detecting the amount of oscillation becomes excessive. Therefore, by determining whether or not the differential value of the displacement signal at this time exceeds a predetermined threshold value, it is possible to detect an abnormality in the load acting on the stylus. Instead of this differential value, a differential value of the moving average value of the displacement signal may be used.

  The present invention provides a surface shape measuring apparatus having a stylus that is in contact with the surface of an object to be measured, thereby enabling detection of an abnormality in a load acting on the stylus, thereby detecting a touch caused by an excessive load acting on the stylus. It becomes possible to prevent breakage of the needle and the pickup.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 4A is a diagram illustrating a schematic configuration example of a calculation unit that controls the surface shape measuring apparatus illustrated in FIGS. 1 and 2 to realize the surface shape measuring apparatus according to the present invention. The other components of the surface shape measuring apparatus according to the embodiment of the present invention are the same as those of the surface shape measuring apparatus 1 shown in FIGS.

  The calculation unit 40 realized by a computer or the like includes a CPU 41 that executes a control program for the surface shape measuring apparatus 1 and a program that processes output signals from the pickup 6 to create surface shape data, and each program by the CPU 41. A main storage device 42 such as a RAM and a ROM for storing data necessary for the execution of the program, a sub storage device 43 for storing each program executed by the CPU 41 and the created surface shape data, and a pickup 6 A displacement signal obtained by converting the output signal into a digital signal by the analog-digital conversion circuit 30 is input to the calculation unit 40, and an interface unit for outputting a control signal for controlling the operation of the movable unit 4 to the moving mechanism drive circuit 50 ( I / F) 44.

FIG. 4B is a functional block diagram realized by the calculation unit 40 shown in FIG. The calculation unit 40 executes a predetermined program stored in the secondary storage device 43 by the CPU 41, thereby at least functional blocks of the surface shape data creation unit 60, the movement mechanism control unit 61, and the stylus load abnormality detection unit 62. Realize.
The surface shape data creation unit 60 sequentially inputs a sequence of displacement signals that change with the movement of the pickup 6, and values of the input displacement signals are input to each point on the line segment of the movement length of the pickup 6. Are sequentially arranged to create surface shape data of the object to be measured.

  The movement mechanism control unit 61 drives the column 3 and the movable part 4 to carry the stylus 11 to the measurement start position, and generates a movement mechanism control command for driving the movable part 4 at a constant speed during the measurement. To the moving mechanism drive circuit 50. Further, the movement mechanism control unit 61 supplies the surface shape data creation unit 60 with data such as the amount of movement of the movable unit 4 and the X coordinate value necessary for creating the surface shape data.

The stylus load abnormality detection unit 62 receives an operation signal indicating that the movement mechanism control unit 61 is driving the column 3 or the movable unit 4, and the movement mechanism control unit 61 drives the column 3 or the movable unit 4. The displacement signal is monitored during the operation. When an abnormality in the displacement signal is detected, a stylus load abnormality signal indicating that there is an abnormality in the load acting on the stylus 11 is generated and output to the surface shape data creation unit 60 and the movement mechanism control unit 61. To do. The surface shape data creation unit 60 that has received the stylus load abnormality signal stops the creation of the surface shape data, and the movement mechanism control unit 61 that has received the stylus load abnormality signal stops driving the column 3 or the movable unit 4.
In the present embodiment, these functional blocks 60 to 62 are realized as software modules that are realized by the CPU 41 executing a predetermined program. However, some or all of these functions are dedicated hardware. It may be realized by a wear circuit.

  FIG. 5A is a diagram illustrating a first configuration example of the stylus load abnormality detection unit 62. The stylus load abnormality detection unit 62 converts a displacement signal sequence, which is a sequence of digital signals obtained by sampling the displacement signal output from the pickup 6 at a predetermined sampling period, into a frequency domain signal, and a fast Fourier transform unit (FFT) 71. And a low frequency component strength measuring unit 72 for detecting a signal strength of a frequency component lower than a predetermined frequency band out of signal strengths at each frequency indicated by the frequency domain signal, and the detected signal strength as a predetermined strength threshold value. The comparison unit 73 that compares with Tfi, and when the detected signal intensity is stronger than the threshold value Tfi, it is determined that there is an abnormality in the change of the displacement signal, and a stylus load indicating that an abnormality in the load acting on the stylus 11 has occurred. A stylus load abnormality signal generation unit 74 that generates an abnormality signal.

Here, since the fast Fourier transform unit (FFT) 71 generates a frequency domain signal by operating while receiving an operation signal from the moving mechanism control unit 61, the stylus load abnormality detection unit 62 Whether or not the load acting on the stylus 11 is always abnormal while the stylus 11 is moved by the column 3 and the movable part 4 as well as while the shape measuring device 1 measures the surface shape. Monitor.
6 (A) and FIG. 6 (B), FIG. 7 (A) to FIG. 7 (C), FIG. 8 (A) to FIG. 8 (C), and FIG. A stylus load abnormality detection method by the stylus load abnormality detection unit 62 shown in FIG. 5 will be described.

FIG. 6A is a view showing a state in which the stylus 11 is caught by the projections and depressions when the cantilever 7 is pulled, and FIG. 6B shows a displacement signal that appears in the state of FIG. It is a graph.
In FIG. 6A, when the stylus 11 is caught by the unevenness of the workpiece W during the pulling operation of the cantilever 7, the stylus 11 rises as indicated by a dotted line, and the cantilever 7 remains upward. It becomes.
For this reason, as shown in FIG. 6B, the displacement signal repeatedly increases and decreases along the undulations on the surface of the workpiece W before time t1 when the stylus 11 is caught by the unevenness of the workpiece W. After t1, the signal value does not decrease while rapidly increasing.

(A) in FIG. 7 is a diagram showing a state in which the stylus is hit against the back of the horizontal hole, and (B) in FIG. 7 is a diagram showing a state in which the stylus is caught by the unevenness when the cantilever is pressed. FIG. 7C is a graph of the displacement signal that appears in the states of FIG. 7A and FIG.
In the state shown in FIG. 7A and FIG. 7B, the cantilever 7 is bent convexly downward. When this is seen from the side of the pickup 6 that detects the swing of the cantilever 7, it becomes the same as the state where the cantilever 7 is facing downward. Therefore, the displacement signal does not rise with the signal value rapidly decreasing as shown in FIG.

8A is a graph of the displacement signal in the time domain, FIG. 8B is a frequency domain signal of the (a) portion of the displacement signal of FIG. 8A, and FIG. 8C is the displacement signal of FIG. (B) The frequency domain signal of the part.
The waveform of the portion (a) in FIG. 8A indicates that the stylus 11 is moved at a constant speed by the movable portion 4 along the surface of the object W to be measured. The signal vibrates according to the surface roughness of the surface of the workpiece W and the speed of the movable part 4. For this reason, when the displacement signal of part (a) in FIG. 8A is converted into a frequency domain signal as shown in FIG. 8B, the displacement signal is mainly measured as shown in FIG. It includes frequency components within a predetermined frequency band f1 to f2 determined by the surface roughness range of the object W and the speed of the movable part 4.

On the other hand, the waveform of part (b) of FIG. 8A shows that the stylus 11 is caught by the irregularities on the surface of the object W to be measured or the stylus 11 hits the back of the horizontal hole at time t1. This shows that the displacement signal does not vibrate while increasing or decreasing. For this reason, when the displacement signal of part (b) of FIG. 8A is converted into a frequency domain signal as shown in FIG. 8C, the displacement signal is converted into a predetermined frequency band f1 as shown in the figure. The frequency component lower than ~ f2 becomes stronger.
Therefore, it is determined whether or not an abnormality has occurred in the load acting on the stylus 11 by converting a displacement signal into a frequency domain signal and detecting a change in signal intensity of a frequency component lower than a predetermined frequency band f1 to f2. it can.

FIG. 9 is a flowchart showing a first example of a stylus load abnormality detection method according to the present invention.
In step S <b> 11, the moving mechanism control unit 61 outputs a moving mechanism control signal to the moving mechanism drive circuit 50 to drive the movable unit 4, and the stylus is placed along the surface of the object W to be measured. 11 and the workpiece W are relatively moved at a constant speed.
In step S12, the pickup 6 detects the displacement of the stylus 11 and generates a displacement signal that is an analog signal. In step S13, the analog-digital conversion circuit 30 samples the output signal of the pickup 6 at a predetermined sampling period and converts it into a digital displacement signal sequence.

In step S14, the fast Fourier transform unit 71 of the stylus load abnormality detection unit 62 shown in FIG. 5A performs a Fourier transform on the displacement signal sequence to generate a frequency domain signal.
In step S <b> 15, the low frequency component intensity detection unit 72 causes the stylus 11 to follow the undulation of the surface of the object W to be measured based on the preset surface roughness of the object W to be measured and the speed setting value of the movable unit 4. The frequency ranges f1 to f2 of the frequency components generated when the stylus 11 and the workpiece W are relatively moved are estimated. And the maximum value of the signal strength in the frequency range lower than the frequency ranges f1 to f2 is detected from the signal strength of each frequency indicated by the frequency domain signal converted by the fast Fourier transform unit 71.
Alternatively, the frequency range f1 to f2 is set in advance in the low frequency component intensity detection unit 72, and the low frequency component intensity detection unit 72 has a preset frequency range out of the signal intensity of each frequency indicated by the frequency domain signal. The maximum value of the signal strength in the frequency range lower than f1 to f2 is detected.

In step S <b> 16, the comparison unit 73 compares the maximum value of the signal intensity detected by the low frequency component intensity detection unit 72 with a predetermined threshold Tfi. That is, it is determined whether or not the maximum value Imax of the signal intensity is within the allowable intensity range (Imax ≦ Tfi). When the maximum value of the signal intensity is equal to or less than the predetermined threshold value Tfi, the process returns to step S11 and the movement of the stylus 11 is continued.
On the other hand, when the maximum value of the signal intensity exceeds the predetermined threshold value Tfi, the stylus load abnormality signal generation unit 74 has an abnormality in the change of the displacement signal and an excessive load is applied to the stylus 11 in step S17. In step S18, a stylus abnormal load signal is output.

In step S <b> 19, the surface shape data creation unit 60 that has received the stylus load abnormality signal stops creating the surface shape data, and the movement mechanism control unit 61 that has received the stylus load abnormality signal receives the column 3 or the movable unit 4. Stop driving.
In step S15, the low frequency component intensity detection unit 72 outputs the average value of the signal intensity in the frequency range lower than the frequency range f1 to f2 instead of outputting the maximum value of the signal intensity in the frequency range lower than the frequency range f1 to f2. May be output.
Further, the stylus load abnormality signal generation unit 74 outputs a stylus load abnormality signal to the movement mechanism control unit 61 to stop the driving of the column 3 or the movable unit 4, and therefore the movement mechanism according to the claims of the present application. Corresponds to the stop.

FIG. 5B is a diagram illustrating a second configuration example of the stylus load abnormality detection unit 62. In this configuration example, it is determined whether or not the frequency component having the maximum intensity included in the displacement signal is within the same allowable frequency range as the frequency ranges f1 to f2.
For this reason, a maximum intensity frequency detection unit 75 that receives the frequency domain signal converted by the fast Fourier transform unit 71 and detects the frequency (maximum intensity frequency) of the maximum intensity frequency component included in the displacement signal is provided.
The comparison unit 73 compares the maximum intensity frequency detected by the maximum intensity frequency detection unit 75 with the upper and lower limit values f1 and f2 of the allowable frequency range, and the maximum intensity frequency is between the allowable frequency ranges f1 and f2. It is determined whether or not there is, and the stylus load abnormality signal generation unit 74 generates a stylus load abnormality signal when the maximum intensity frequency is not between the allowable frequency ranges f1 and f2.
Alternatively, the comparison unit 73 compares the maximum intensity frequency fmax detected by the maximum intensity frequency detection unit 75 with the lower limit value f2 of the allowable frequency range, so that the maximum intensity frequency fmax is within the allowable frequency range (fmax ≧ f2). When the maximum intensity frequency fmax is lower than f2, the stylus load abnormality signal generation unit 74 generates a stylus load abnormality signal.

  FIG. 10A and FIG. 10B are graphs showing changes in the displacement signal and its differential value. As shown in FIG. 10A, before the time t1 when the stylus 11 is caught by the unevenness of the workpiece W, the displacement signal has a certain finite change rate according to the undulation of the surface of the workpiece W. When the increase / decrease is repeated, the signal value rapidly increases (or decreases) after time t1. Therefore, as shown in FIG. 10B, the differential value of the displacement signal changes within a certain range before time t1, but rapidly changes after time t1.

Therefore, in the third example of the stylus load abnormality detection unit 62 shown below, when the differential value of the displacement signal is calculated and this differential value exceeds a predetermined threshold value Ti, the change in the displacement signal is abnormal, and the stylus 11 is determined that an excessive load is acting.
FIG. 11A is a diagram illustrating a third configuration example of the stylus load abnormality detection unit 62. The stylus load abnormality detection unit 62 includes a differential calculation unit 76 that calculates the absolute value of the differential value of the input displacement signal, and the absolute value of the differential value calculated by the differential calculation unit 76 is set to a predetermined threshold value by the comparison unit 73. Compared with Ti, the stylus load abnormality signal generation unit 74 generates a stylus load abnormality signal when the absolute value of the differential value is larger than a predetermined threshold value Ti.
The differential calculation unit 76 always outputs the absolute value of the differential value of the displacement signal while receiving the operation signal from the moving mechanism control unit 61. Therefore, the stylus load abnormality detection unit 62 is not always applied to the stylus 11 while the stylus 11 is moved by the column 3 and the movable unit 4 as well as the surface shape measuring device 1 is measuring the surface shape. Monitor whether the applied load is abnormal.

FIG. 12 is a flowchart showing a second example of the stylus load abnormality detection method according to the present invention. Similarly to the abnormality detection method shown in FIG. 9, the moving mechanism control unit 61 drives the movable unit 4 in step S11, and the pickup 6 generates a displacement signal in step S12. In step S13, the analog-digital conversion circuit 30 converts the output signal of the pickup 6 into a digital displacement signal string.
In step S21, the differential calculation unit 76 calculates the absolute value of the differential value of the input displacement signal. In step S22, the comparison unit 73 compares the absolute value of the differential value with a predetermined threshold value Ti. If the absolute value of the differential value is less than or equal to the predetermined threshold value Ti, the process returns to step S11 and the stylus 11 moves. Continue.

On the other hand, when the absolute value of the differential value exceeds the predetermined threshold value Ti, in step S17, the stylus load abnormality signal generation unit 74 has an abnormality in the change of the displacement signal and an excessive load is acting on the stylus 11. In step S18, a stylus abnormal load signal is output.
In step S <b> 19, the surface shape data creation unit 60 that has received the stylus load abnormality signal stops creating the surface shape data, and the movement mechanism control unit 61 that has received the stylus load abnormality signal receives the column 3 or the movable unit 4. Stop driving.

In actual measurement, if the displacement signal obtained by digitally converting the output signal of the pickup 6 is directly differentiated, the displacement signal changes too much, and the normal measurement state and the stylus 11 are obstructed such as irregularities on the surface of the measurement object. It may be difficult to distinguish from a state of being caught on an object.
Therefore, instead of calculating the absolute value of the differential value of the displacement signal in step S21, the absolute value of the differential value of the moving average value of the displacement signal is calculated and compared with a predetermined threshold value Ti in step S22. Thus, an abnormality in the change of the displacement signal may be detected.
FIG. 11B is a diagram illustrating a fourth configuration example of the stylus load abnormality detection unit 62. In this configuration example, in order to calculate the moving average value of the displacement signal, a moving average unit 77 realized by a digital filter or the like is provided, and the differential operation unit 76 calculates the moving average value of the displacement signal calculated by the moving average unit 77. The derivative value of is output.

  The present invention relates to a surface shape measuring apparatus for measuring the surface shape of a measurement object by moving the measurement object and the stylus while moving the stylus along the surface of the measurement object. The present invention relates to a technique for preventing breakage of a pickup unit that detects displacement of a needle.

It is a basic lineblock diagram of a surface shape measuring device. It is the schematic which shows the internal structure of a pick-up. (A) is a figure which shows a mode that a stylus collides in the back of the horizontal hole of a to-be-measured object, (B) is a figure which shows a mode that a stylus is caught in the hole of a to-be-measured object. (A) is a figure which shows the schematic structural example of the calculation part which controls the surface shape measuring apparatus shown in FIG.1 and FIG.2, and implement | achieves the surface shape measuring apparatus by this invention, (B) is a figure to (A). It is a functional block diagram implement | achieved by the calculation part shown. (A) And (B) is a figure which shows the 1st and 2nd structural example of a stylus load abnormality detection part, respectively. (A) is a figure which shows a mode that the stylus was caught by the unevenness | corrugation when pulling a cantilever, (B) is a graph of the displacement signal which appears in the state of (A). (A) is a figure which shows a mode that the stylus was struck in the back of a horizontal hole, (B) is a figure which shows a mode that the stylus was caught by the unevenness | corrugation when pushing the cantilever, (C) ) And (C) are graphs of displacement signals appearing in the states. (A) is a graph of the displacement signal in the time domain, (B) is a frequency domain signal of (a) part of the displacement signal of (A), (C) is (b) of the displacement signal of (A). This is the frequency domain signal of the part. It is a flowchart which shows the 1st example of the abnormality detection method of the stylus load by this invention. (A) And (B) is a graph which shows the change of a displacement signal and its differential value. (A) And (B) is a figure which shows the 3rd and 4th structural example of a stylus load abnormality detection part, respectively. It is a flowchart which shows the 2nd example of the abnormality detection method of the stylus load by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface shape measuring apparatus 2 Table 3 Column 4 Movable part 6 Pickup 7 Cantilever 10 Arm part 11 Stylus

Claims (14)

The stylus is moved relative to the surface of the object to be measured, and at this time, a displacement signal is generated to detect the displacement of the stylus caused by the undulation of the surface of the object to be measured, and the surface shape of the object to be measured A surface shape measuring device for measuring
A surface shape measuring apparatus, comprising: a stylus load abnormality detection unit that detects an abnormality in change of the displacement signal as an abnormality in a load acting on the stylus. A moving mechanism for relatively moving the object to be measured and the stylus;
A movement mechanism stop unit for stopping the movement mechanism when the stylus load abnormality detection unit detects the load abnormality;
The surface shape measuring device according to claim 1, comprising:   The stylus load abnormality detection unit includes a Fourier transform unit that converts the displacement signal into a frequency domain signal, and when the change of the frequency domain signal obtained by converting the displacement signal exceeds a predetermined allowable width, the displacement The surface shape measuring apparatus according to claim 1, wherein it is determined that the change in the signal is abnormal.   The surface shape measuring apparatus according to claim 3, wherein the predetermined allowable width is defined as an allowable intensity range of a frequency signal component lower than a predetermined frequency band included in the frequency domain signal.   A signal that is expected to occur in the frequency domain signal when the stylus and the object to be measured are moved relative to each other while the stylus is moved along the undulations on the surface of the object to be measured. The surface shape measuring device according to claim 4, wherein the surface shape measuring device is defined as a frequency range of   The surface shape measuring apparatus according to claim 3, wherein the predetermined allowable width is defined as an allowable frequency range of a frequency having a frequency component having a maximum intensity. A lever member that swingably supports the stylus, and a displacement sensor that detects the swing amount of the lever member and generates the displacement signal,
The stylus load abnormality detection unit determines that there is an abnormality in the change of the displacement signal when either the differential value of the displacement signal or the differential value of the moving average value exceeds a predetermined threshold value. The surface shape measuring apparatus according to claim 1 or 2. The stylus is moved relative to the surface of the object to be measured, and at this time, a displacement signal is generated to detect the displacement of the stylus caused by the undulation of the surface of the object to be measured, and the surface shape of the object to be measured In the surface shape measurement for measuring the stylus load abnormality detection method for detecting an abnormality of the load acting on the stylus,
An abnormality detection method, wherein an abnormality in change of the displacement signal is detected as an abnormality in a load acting on the stylus.   The abnormality detection method according to claim 8, wherein when the load abnormality is detected, the relative movement between the object to be measured and the stylus is stopped. Converting the displacement signal into a frequency domain signal;
When the change of the frequency domain signal exceeds a predetermined allowable range, it is determined that the change of the displacement signal is abnormal.
The abnormality detection method according to claim 8 or 9, characterized in that.   The abnormality detection method according to claim 10, wherein the predetermined allowable width is determined as an allowable intensity range of a frequency signal component included in the frequency domain signal and lower than a predetermined frequency band.   A signal that is expected to occur in the frequency domain signal when the stylus and the object to be measured are moved relative to each other while the stylus is moved along the undulations on the surface of the object to be measured. The abnormality detection method according to claim 11, wherein the abnormality detection method is defined as a frequency range.   The abnormality detection method according to claim 10, wherein the predetermined change width of the frequency domain signal is defined as an allowable frequency range of a frequency having a frequency component having a maximum intensity. Detecting a swing amount of a swingable lever member supporting the stylus to generate the displacement signal;
The abnormality according to claim 8 or 9, wherein when any one of the differential value of the displacement signal and the differential value of the moving average value exceeds a predetermined threshold, it is determined that the change in the displacement amount is abnormal. Detection method.

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