JP3832061B2 - Ultrasonic dimension measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dimension measuring apparatus using ultrasonic waves.
[0002]
[Prior art]
When a groove is processed on a surface of a ceramic substrate or the like or cut into a narrow width, it may be necessary to measure the width between the grooves or the cut width with high accuracy. Conventionally, such dimension measurement is performed using an optical microscope.
[0003]
[Problems to be solved by the invention]
However, with an optical microscope, it is difficult to measure dimensions with high accuracy, and for example, it is impossible to measure dimensions of 1 μm or less. For this reason, in measuring dimensions of electronic parts, etc., the quality was determined by looking at the electrical characteristics depending on the dimensions. However, this method requires time and effort, so the dimensions are measured during processing. The width could not be corrected.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic dimension measuring apparatus that can measure the dimension of an object to be measured with high accuracy and can measure instantaneously even during processing.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an apparatus for immersing a measurement object having two parallel opposite end surfaces in a liquid and measuring the dimension between the two end surfaces of the measurement object. A plane wave is transmitted to the surface of the object to be measured, and a surface acoustic wave is generated on the surface of the object to be measured, and a projection line on the surface of the object to be measured in the transmission direction of the plane wave is perpendicular to the two opposite end faces of the object to be measured. The reflected ultrasonic wave reflected at a predetermined point on the surface of the object to be measured and the surface acoustic wave propagating on the surface of the object to be measured are reflected on the two opposite end surfaces of the object to be measured, and then An ultrasonic receiver for receiving radiated ultrasonic waves radiated from a predetermined point, and means for obtaining a dimension between two end faces of the object to be measured from a reception time difference between the reflected ultrasonic waves and the radiated ultrasonic waves It is.
[0006]
A plane wave is transmitted from the ultrasonic transmitter to the object to be measured immersed in the liquid from an oblique direction. As an ultrasonic transmitter, it can comprise by the combination of a piezoelectric element and a plane lens, for example. The object to be measured is immersed in the liquid in order to transmit ultrasonic waves from the transmitter to the object to be measured, and a liquid having a relatively small viscosity coefficient (for example, water) is used. When a plane wave is incident on the surface of the object to be measured from the transmitter, a part of the plane wave is reflected by the surface and received by the ultrasonic receiver. This is reflected ultrasound. On the other hand, when the incident angle of the plane wave is set to a predetermined critical angle, the surface acoustic wave is excited, and this surface acoustic wave propagates through the surface of the object to be measured. Since the projection line on the surface of the object to be measured in the transmission direction of the plane wave is set in a direction perpendicular to the two opposite end faces of the object to be measured, after the surface acoustic wave is reflected by one end face of the object to be measured, The light is also reflected at the opposite end faces and returns to a predetermined point where the plane wave is incident. This surface acoustic wave propagates through the surface of the object to be measured while radiating ultrasonic waves into the liquid. Then, by adjusting the focal point of the ultrasonic receiver to a predetermined point where the plane wave is incident, the radiated ultrasonic wave radiated from the surface acoustic wave returning to the predetermined point can be accurately received. For example, the ultrasonic receiver can be configured by a combination of a piezoelectric element and a spherical lens.
The dimension between the two end faces of the object to be measured can be obtained from the difference in arrival time between the reflected ultrasonic wave and the emitted ultrasonic wave. That is, when the arrival time of the reflected ultrasonic wave is t ₁ , the arrival time of the emitted ultrasonic wave is t ₂ , and the velocity of the surface acoustic wave is V, the dimension L of the object to be measured (distance between two opposite end surfaces) is Can be sought.
L = V × (t ₂ −t ₁ ) / 2
[0007]
In addition, as described in claim 2, the plane wave is continuously transmitted from the transmitter, and the incident surface acoustic wave and the reflected surface acoustic wave are caused to interfere with each other by changing the wavelength of the plane wave to be transmitted. The dimension between the two end surfaces of the object to be measured may be obtained from the wavelength of the ultrasonic wave that generates a large radiated ultrasonic wave. In this case, since the difference for one ultrasonic wave can be detected, the resolution can be increased to within one wavelength.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram illustrating the principle of an ultrasonic dimension measuring apparatus according to the present invention.
In the figure, reference numeral 1 denotes a storage tank in which a liquid 2 having a viscosity of, for example, 4.0 × 10 ⁻³ Pa · S (4CP) or less is stored, and an object to be measured 3 is immersed in the liquid 2. Has been. In this embodiment, for example, a rectangular piezoelectric ceramic substrate is used as the DUT 3.
[0009]
Reference numeral 4 denotes an ultrasonic transmitter, which includes a piezoelectric element 5 and a pulse generator 6 each of which is a flat lens partly immersed in the liquid 2. The piezoelectric element 5 is excited by a pulse output from the pulse generator 6, and a plane wave (ultrasonic wave of several tens of MHz or more) U ₁ is emitted toward the DUT 3. Reference numeral 7 denotes an ultrasonic receiver, which is composed of a piezoelectric element 8 made of a spherical lens partially immersed in the liquid 2 and an oscilloscope 9 and receives ultrasonic waves reflected by the object to be measured 3.
[0010]
The planar lens 5 and the spherical lens 8 are held in a predetermined direction by a lens holder 10. That is, the planar lens 5 can irradiate a predetermined area including the incident point P of the DUT 3 with the plane wave U ₁ so that the reflected wave from the incident point P is received most strongly by the spherical lens 8. In addition, the focal point of the spherical lens 8 is adjusted. The lens holder 10 can adjust the angle in the direction of arrow A around the incident point P, and the incident angle θ of the plane wave U ₁ incident on the surface of the DUT 3 from the plane lens 5 is variable. Note that the orientation of the planar lens 5 is set so that the projection line of the plane wave U _{1 in} the transmission direction onto the surface of the object 3 to be measured is always perpendicular to the opposing two end faces 3a and 3b of the object 3 to be measured. Has been. In this embodiment, the projection line on the surface of the device under test 3 in the receiving direction of the receiver 7 is also set perpendicular to the two opposing end faces of the device under test 3.
[0011]
Here, a measuring method of the ultrasonic dimension measuring apparatus having the above-described configuration will be described.
First, the lens holder 10 is rotated to vary the incident angle θ of the plane wave U ₁ incident on the surface of the DUT 3 from the plane lens 5. When the incident angle θ reaches a certain critical angle, a surface acoustic wave is generated on the surface of the DUT 3 by the plane wave U _{1. The} lens holder 10 is positioned at an angle at which the surface wave is generated. A part of the plane wave U ₁ irradiated from the plane lens 5 is reflected by the surface of the object to be measured 3 (reflected ultrasonic wave U ₂ ) and received by the spherical lens 8. On the other hand, the surface acoustic wave E ₁ excited by the plane wave U ₁ propagates in the direction of one end face 3a along the surface of the object to be measured 3 as shown in FIG. 2, reflects on the end face 3a, and then the other end face. Propagates in the 3b direction. This surface acoustic wave is a Rayleigh wave that propagates through the surface of the object 3 while radiating ultrasonic waves into the liquid. When the surface acoustic wave E ₂ reflected by the end face 3 b returns to the irradiation point P, the ultrasonic wave (radiated ultrasonic wave U ₃ ) radiated in the liquid is received by the spherical lens 8.
[0012]
FIG. 2 shows received waveforms of the reflected ultrasonic wave U ₂ and the emitted ultrasonic wave U ₃ , and the arrival time of the reflected ultrasonic wave U ₂ is t ₁ and the arrival time of the emitted ultrasonic wave U ₃ is t ₂ .
Both waves U _2, the time difference t ₂ -t ₁ of the U _3, the surface acoustic wave E _1, E ₂ is proportional to the distance 2L propagated and is inversely proportional to the propagation velocity V of the surface acoustic wave E _1, E _2. Therefore, the distance L between the end surfaces 3a and 3b of the DUT 3 is obtained by the following equation.
L = V × (t ₂ −t ₁ ) / 2
[0013]
Further, the propagation velocity V of the surface acoustic waves E ₁ and E ₂ is given by the following equation according to the elastic constant M and the density ρ of the DUT 3.
V = √ (M / ρ)
[0014]
In addition to the above measuring method or separately from the above measuring method, the following measuring method may be carried out.
That is, the wavelength of the plane wave U ₁ to be transmitted is changed while continuously transmitting the plane wave U ₁ from the transmitter 4 to the DUT 3. FIG. 3A shows a waveform in a state where the incident surface acoustic wave E ₁ and the reflected surface acoustic wave E ₂ do not resonate, and the actual surface acoustic wave becomes a solid line. When the wavelength of the plane wave U ₁ to be transmitted reaches a certain wavelength, the incident surface wave E ₁ and the reflected surface wave E ₂ resonate (interfere), and the actual surface acoustic wave rapidly changes as shown in FIG. growing. Therefore, the ultrasonic wave U ₃ whose amplitude is increased from the surface of the DUT 3 by the resonated surface acoustic wave is radiated and received by the spherical lens 8. That is, when the dimension 2L of the object to be measured 3 is an integral multiple of the wavelength λ of the ultrasonic wave, the resonance with the highest intensity occurs. Therefore, by obtaining the wavelength λ when the resonance with the highest intensity occurs, the distance 2L is obtained. I can know.
2L = n · λ (n: positive integer)
In this method, when an approximate dimension exceeding one ultrasonic wavelength λ is known, the measurement can be performed with the resolution increased to within one wavelength.
[0015]
FIG. 4 shows an example in which the dimension measuring apparatus of the present invention is applied to the groove processing.
Grooves 21 are machined on the surface of the DUT 3 at regular intervals by the grindstone 20. The storage tank 1 storing the liquid 2 is placed on an XY-axis movable table 22 that is movable in the left-right direction. The movable table 22 is driven in the X and Y axis directions by a driving device (not shown) such as a motor. The movable table 22 moves only in the Y-axis direction during the processing of the grindstone 20, and when the processing of one groove 21 is completed, the movable table 22 moves in the X-axis direction by a predetermined width.
[0016]
The pulse generator 6 and the oscilloscope 9 are each connected to a controller 23, and the driving device is driven based on a machining position command signal from the controller 23. That is, the controller 23 obtains the interval D of the groove 21 of the object to be measured 3 from the time difference (t ₂ −t ₁ ) between the reflected ultrasonic wave U ₂ and the emitted ultrasonic wave U ₃ in the same manner as described above. If it is within the range, it is G (good), and if it is out of the standard range, it is NG (bad). In the case of NG, the amount of movement of the movable table 22 in the X-axis direction is adjusted.
[0017]
Thus, since the dimension D of the DUT 3 can be measured with high accuracy and instantaneously during machining, even if NG occurs once, the machining position command signal can be corrected to G in the next machining. High-precision processing becomes possible, and the accuracy can be maintained.
[0018]
The shape of the object to be measured may be any shape as long as it has two parallel end surface portions that reflect surface acoustic waves on at least a part of the surface, and the entire facing two end surfaces do not need to be parallel. In the present invention, the term “parallel” is not limited to strict parallelism, but may have any degree of parallelism that allows the reflected wave to be reflected without being scattered, and includes some angle variation.
The material of the object to be measured only needs to have an elastic coefficient that allows surface acoustic waves to propagate through the surface and be reflected at both end faces, and the surface portion is preferably homogeneous.
The receiving point of the receiver may be in an area where the plane wave transmitted from the transmitter reaches the device under test. In addition, the projection line on the surface of the object to be measured in the receiving direction of the receiver does not necessarily need to be perpendicular to the two opposing end surfaces of the object to be measured, and depends on the performance of the spherical lens.
[0019]
Further, the present invention can measure not only the dimension of the object to be measured but also the surface condition such as chipping generated at the end of the object to be measured. That is, if there is chipping or the like at the end of the object to be measured, the reflected wave is disturbed, so the surface state can be detected by detecting the distortion of the received waveform.
[0020]
【The invention's effect】
As is clear from the above description, according to the present invention, the reflected ultrasonic wave reflected by the surface of the object to be measured and the radiated ultrasonic wave by the surface acoustic wave propagated through the surface of the object to be measured and reflected by both end surfaces are obtained. Since the dimension between the two end faces of the object to be measured is obtained from the arrival time difference, the dimension of the object to be measured can be measured with high accuracy. In addition, since measurement can be performed instantaneously even during machining such as grooving or cutting, high-precision machining can be realized by correcting machining errors.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the principle of an ultrasonic dimension measuring apparatus according to the present invention.
FIG. 2 is a diagram showing the behavior of an ultrasonic wave and a surface acoustic wave transmitted through an object to be measured.
FIG. 3 is a waveform diagram of a surface acoustic wave at non-resonance and at resonance.
FIG. 4 is a diagram in which the ultrasonic dimension measuring device of the present invention is applied to a groove processing machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Storage tank 2 Liquid 3 Measured object 4 Ultrasonic transmitter 5 Piezoelectric element (planar lens)
6 Pulse generator 7 Ultrasonic receiver 8 Piezoelectric element (spherical lens)
9 Oscilloscope

Claims (2)

An apparatus for measuring a dimension between two end faces of a measurement object by immersing the measurement object having two opposite end faces in parallel in a liquid,
A plane wave is transmitted to the object to be measured, a surface acoustic wave is generated on the surface of the object to be measured, and a projection line on the surface of the object to be measured in the transmission direction of the plane wave is directed to the two opposite end faces of the object to be measured. An ultrasonic transmitter that is vertically oriented;
The reflected ultrasonic wave reflected at a predetermined point on the surface of the object to be measured and the surface acoustic wave propagating on the surface of the object to be measured are reflected at the two opposite end faces of the object to be measured, and then radiated from the predetermined point. An ultrasonic receiver for receiving sound waves;
Means for determining a dimension between two end faces of the object to be measured from a reception time difference between the reflected ultrasonic wave and the emitted ultrasonic wave. An apparatus for measuring a dimension between two end faces of a measurement object by immersing the measurement object having two opposite end faces in parallel in a liquid,
A plane wave U1 is transmitted to the object to be measured, and a surface acoustic wave E1 is generated on the surface of the object to be measured, and projection lines on the surface of the object to be measured in the transmission direction of the plane wave are formed on two opposite end surfaces of the object to be measured. An ultrasonic transmitter that is oriented perpendicular to the
After the surface wave U1 propagating on the surface of the object to be measured is reflected by the two opposite end faces of the object to be measured by the incidence of the plane wave U1, the radiated ultrasonic wave U3 radiated from a predetermined point on the surface of the object to be measured is generated. An ultrasonic receiver to receive,
Means for obtaining a dimension between two end faces of the object to be measured from the plane wave U1 and the radiation ultrasonic wave U3,
The plane wave U1 is continuously transmitted from the transmitter, and the incident surface acoustic wave E1 and the reflected surface acoustic wave E2 are caused to interfere with each other by changing the wavelength λ of the plane wave U1 to be transmitted. An ultrasonic dimension measuring apparatus for obtaining a dimension between two end faces of an object to be measured from a wavelength λ of a plane wave U1 when a sound wave U3 is generated.

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