JPH08320208A - Displacement meter - Google Patents

Abstract

PURPOSE: To measure the displacement of the surface of an object to be measured at high precision even through a light transmissive material. CONSTITUTION: A displacement meter consists of a laser diode 12 to radiate light rays to an object to be measured 16 and a second light rays limiting diaphragm part 29 arranged so as to move relatively to a lens 15 installed between the laser diode 12 and the object to be measured 16 and moreover the meter is provided with a tuning fork 21 to vibrate the lens 15, a pin hole 17a where reflected light rays from the object to be measured 16 pass, a photodiode 18 to receive light rays which pass the pin hole 17a, a computing part 20 to capture a detected position signal of the lens 15 at the time when the quantity of light rays reception by the photodiode 18 becomes the maximum, and a distance conversion part 50 to convert the captured detected position signal into the distance.

Description

Detailed Description of the Invention

[0001]

The present invention relates to, for example, metals, resins,
The present invention relates to a displacement meter that projects light onto the surface of an object to be measured, such as paper or ceramic, to measure the displacement of the surface of the object to be measured. However, the “surface” used here means a surface on which projected light is reflected, that is, an interface. For example, when light is projected on a translucent substance such as glass, reflection occurs on the front surface and the back surface of the glass, but both of these two surfaces are regarded as the front surface.

[0002]

2. Description of the Related Art As a device for measuring the displacement of the surface of an object to be measured, such as metal or resin, for example, a focus detection type non-contact displacement meter has been put into practical use. Figure 13 shows the magazine "Optical Technology Contact V"
ol. 26, No. 11 (1988) ”on page 775, is a schematic configuration diagram of a focus detection type non-contact displacement meter by the Foucault method. The light emitted from the laser diode 1 passes through the lens 2, the light wave splitting prism 3, and the lens 4 and is projected onto the DUT 5.

The reflected light from the object to be measured 5 is reflected by the light wave splitting prism 3 and then passes through the light wave splitting prism 6 to detect the in-focus point of the light projected on the object to be measured 5. Each photodiode is divided into two. It is incident on 7a and 7b. The electric signal photoelectrically converted by the photodiodes 7a and 7b is a differential amplifier 8
Is input to. The control unit 9 includes a lens position control circuit 9a, a data processing circuit 9b, and a display circuit 9c,
The output signal of the differential amplifier 8 is input to the lens position control circuit 9a. The control signal output from the lens position control circuit 9a is applied to the electromagnetic coil 10 that moves the lens 4 up and down in the optical axis direction.

Next, the operation of this non-contact displacement meter will be described.
When light is projected from the laser diode 1 to the DUT 5,
The reflected light from the DUT 5 is reflected by the light wave splitting prism 3 and enters the photodiodes 7a and 7b. When the distance between the lens 4 and the DUT 5 changes, the divergence angle of the reflected light beam from the DUT changes and the photodiodes 7a,
There is a difference in the amount of light received by 7b. Then, a signal corresponding to the difference in the amount of received light is output from the differential amplifier 8 and input to the lens position control circuit 9a. When the focus of the light emitted from the laser diode 1 is generated on the DUT 5, the light receiving amounts of the photodiodes 7a and 7b become equal, and the output signal of the differential amplifier 8 disappears.

In this way, the photodiodes 7a, 7a
Based on the amount of light received by b, it is detected whether or not the focused point of the light emitted from the laser diode 1 is generated on the object to be measured. Therefore, the electromagnetic coil 10 is driven by the control signal from the lens position control circuit 9a so that the light receiving amounts of the photodiodes 7a and 7b become equal, that is, the in-focus object is generated, and the position of the lens 4 is moved up and down. When moved, the control amount for moving the lens up and down corresponds to the displacement of the surface of the measured object, and the displacement of the surface of the measured object is measured by the controlled amount.

However, when the light projected on the object to be measured 5 dips into the object to be measured 5, that is, when so-called descent light is generated, the surface of the object to be measured 5 spreads three-dimensionally due to the latent light. By the way, two photodiodes 7
Each of a and 7b receives the light having the in-focus point and the light expanded by the latent light, which causes a difference in the amount of light received by the photodiodes 7a and 7b. Here,
The "diving light" is different from the light reflected by the "surface" described above. For example, the light that enters the substance and is reflected at a portion other than the interface and that goes out of the substance is the reflected light by the "surface". Without saying, it becomes "diving light".

On the other hand, when stray light is generated in the laser diode 1 or the like separately, stray light is projected near the position where the focal point is generated on the surface of the object 5 to be measured, so that the two photodiodes 7a are formed. , 7b receive the light having the in-focus point and the light due to the stray light, and in this case as well, a difference occurs in the amount of light received by the photodiodes 7a, 7b. Therefore, in the case where the undergrowth light or the stray light is generated, even if the focal point of the light emitted from the laser diode 1 is generated in the DUT 5, the light receiving amounts of the two photodiodes 7a and 7b are not equal, and There is a problem that an error occurs in the measured value of the displacement of the surface of the measurement object 5. The stray light referred to here is undesired light generated due to a cause other than regular refraction or reflection generated in the optical device.

To solve this problem, a measuring method as shown in FIG. 1 has been proposed. As shown in FIG. 1, the emitted light from the laser diode C is converged and projected on the object to be measured B through the beam splitter D, the lens L and the lens A. When the lens A is vibrated with a predetermined amplitude in the optical axis direction shown by the arrow, the position of the lens A changes as shown by a curve Q in FIG. Then, the distance between the lens A and the measured object B changes. The reflected light from the object to be measured B is beam splitter D.
And is incident on the light receiving portion E through the optical stop portion F. Within one cycle of the vibration of the lens A, the focal point of the light projected on the measured object B occurs twice on the measured object B, and each time the focused point occurs, the amount of light received by the light receiving section E becomes maximum. That is, when the lens A and the object B to be measured reach a predetermined distance, a focused point is generated on the object B to be measured.

Therefore, the displacement (height) of the surface of the object to be measured B is measured.
When the light is projected to the height position of low, assuming that there are three stages of high, middle, and low, the object to be measured at each time point before and after the lens A comes closest to the object to be measured B. Focusing occurs on B, the amount of light received by the light receiving section E becomes maximum, and focusing detection signals Z, Z are generated as shown in FIG. Further, when the light is projected at the middle height position, the in-focus point is generated on the object to be measured B at an intermediate point between the time when the lens A is closest to the object B to be measured and the time when the lens A is farthest from the object. The amount of light received by the light receiving section E becomes maximum, and the in-focus detection signals Z, Z are generated as shown in FIG. Further, when the light is projected at a high height position, the in-focus point is generated on the measured object B before and after the lens A is farthest from the measured object B, and the measured object B is focused. The amount of received light becomes maximum, and as shown in FIG.
Z occurs. Thus, the position of the lens A at the time when the in-focus detection signals Z, Z are generated, that is, the amplitude of the lens A corresponds to the distance from the reference position of the optical system to the object to be measured, and the object B to be measured is the optical axis. By moving in a direction orthogonal to each other, the displacement of the surface of the object to be measured B can be measured.

The structure and operation of this conventional displacement meter will be described in detail below with reference to the drawings. FIG. 4 is a schematic configuration diagram of a conventional displacement meter. The emitted light of the laser diode 12 driven by the laser power control circuit 11 sequentially passes through the beam splitter 13, the lens 14 and the lens 15,
The object 16 to be measured is projected. The reflected light from the DUT 16 passes through the lens 15 and the lens 14, is reflected by the beam splitter 13, and enters the photodiode 18 through the pinhole 17a of the optical diaphragm 17 which forms the pinhole 17a. It is like this. The size φ of the pinhole 17a is selected to be as small as possible by the following formula. The pinhole used here refers to a hole having a small size of about several micrometers in diameter, and has the same size as the beam diameter of the emitted light converged by the lens. φ = 0.61 × wavelength of laser diode light / NA (1) where NA is a numerical aperture, which is a constant shown in the optical system. This equation is derived from "Rayleigh resolution limit".

The signal photoelectrically converted by the photodiode 18 is input to the amplifier 19, and its output signal X is input to the arithmetic unit 20. A peripheral edge portion of the lens 15 is attached to the tip of one long side portion of the U-shaped tuning fork 21. The lens 15 is made to vibrate with a predetermined amplitude in the optical axis direction of the light emitted from the laser diode 12 by the vibration of the tuning fork 21. The tuning fork amplitude detector 2 serving as a position detecting unit, which is composed of, for example, a sensor using magnetism, light, or electrostatic capacitance, is provided on the side of the tip of the tuning fork 21 on one side.
2 is provided and the amplitude of the tuning fork 21, that is, the lens 1
The position 5 is detected. The detection amplitude signal detected by the tuning fork amplitude detector 22 is input to the amplifier 23,
The output signal Y is input to the arithmetic unit 20. A solenoid 24 for vibrating the tuning fork 21 is disposed on the side of the other end of the tuning fork 21 on the tip side.

The solenoid 24 has a tuning fork amplitude control circuit 25.
The control current is supplied to the tuning fork amplitude control circuit 25, and the output signal of the amplifier 23 is applied to the tuning fork amplitude control circuit 25 so that the amplitude of the tuning fork 21 is controlled to be constant. Arithmetic unit 20
The displacement signal captured and output by is input to the distance conversion unit 50.

FIG. 5 is a block diagram showing the configuration of the arithmetic unit 20. The output signal X of the amplifier 19 (see FIG. 4) input to the arithmetic unit 20 is input to the differentiator 30 and the positive input terminal + of the first comparator 31. The reference voltage Vref is input to the negative input terminal-of the comparator 31. The output signal S30 of the differentiator 30 is input to the negative input terminal − of the second comparator 32. The positive input terminal + of the comparator 32 is grounded.
The output signals S31 and S32 of the comparators 31 and 32 are input to the one input terminal and the other input terminal of the AND circuit 33, respectively, and the output signal S33 is input to the one-shot pulse generation circuit 34. The one-shot pulse S34 output from the one-shot pulse generation circuit 34 is given to the switch SW as an on / off control signal.

Output signal Y from amplifier 23 (see FIG. 4)
Is an amplifier 36 via the amplifier 35 and the switch SW.
Is input to. The input side of the amplifier 36 is grounded via the capacitor 37. A sample hold circuit 38 is configured by the amplifier 36 and the capacitor 37, and the displacement signal S38 is output from the amplifier 36.

Next, the operation of the displacement gauge thus constructed will be described. When a current is supplied to the solenoid 24 from the tuning fork amplitude control circuit 25, a magnetic field is generated by the solenoid 24. The generated magnetic field causes the tuning fork 21 to vibrate with a predetermined amplitude,
The lens 15 is vibrated in the optical axis direction of the light passing through it.
The tuning fork amplitude detector 22 detects the amplitude of the tuning fork 21, that is, the lens 15
Of the sine wave signal which is the amplitude of the lens 15 is output. The sine wave signal is amplified by the amplifier 23, and the output signal Y output from the amplifier 23 is input to the arithmetic unit 20.

On the other hand, when a drive current is supplied from the laser power control circuit 11 to the laser diode 12, the laser diode 12 emits laser light. The emitted light passes through the beam splitter 13, the lens 14 and the lens 15 and is projected onto the DUT 16. The reflected light reflected by the DUT 16 passes through the lens 15 and the lens 14, is reflected by the beam splitter 13 and is projected to the optical diaphragm 17 side, and only the light transmitted through the pinhole 17a enters the photodiode 18. Therefore, the photodiode 18 is
The reflected light due to the stray light generated in 1) and the stray light generated in the laser diode 12 is blocked by the pinhole 17a and does not pass through the pinhole 17a.
Only the in-focus light generated in 6 will be incident.

By the way, since the lens 15 is vibrated, the distance between the lens 15 and the object 16 to be measured changes, and when the predetermined distance is reached, the focal point of the light projected on the object 16 to be measured is changed. When it occurs on the device under test 16, the photodetection output of the photodiode 18 instantly becomes maximum, and a signal corresponding to this photodetection output is input to the amplifier 19, and the amplifier 19 outputs the signal shown in FIG.
The output signal X shown in (a) is output and input to the arithmetic unit 20.

When the output signal X and the output signal Y are input to the arithmetic unit 20 in this way, the output signal X is differentiated by the differentiator 30 and the inverse S as shown in FIG. An output signal S30 having a letter-shaped differential waveform is output. Then, the maximum value of the output signal X is detected by the zero-cross time point T0 of the output signal S30, and the time point at which the focus of the light projected on the DUT 16 is accurately detected. The output signal S30 is input to the comparator 32, and the comparator 32 compares the output signal S30 with the ground potential, and the comparator 32 outputs the output signal S30 at the zero-cross point T.
The output signal S3 of the pulse shown in FIG. 6D having a pulse width corresponding to the period of the negative half cycle of the output signal S30
2 is output.

On the other hand, the comparator 31 compares the output signal X and the reference voltage Vref in magnitude, and the pulse width corresponding to the period when the output signal X is equal to or higher than the reference voltage Vref from the comparator 31 is shown in FIG. 6C. The output signal S31 shown in is output. AND when the logic of these output signals S31 and S32 is established
From the circuit 33 to the pulse output signal S33 shown in FIG.
Is output and input to the one-shot pulse generation circuit 34. As a result, the one-shot pulse generation circuit 34 outputs the one-shot pulse S34 shown in FIG. 6 (f) which rises in synchronization with the rising of the output signal S33. Then, the switch SW is turned on by the one-shot pulse S34.

Then, the output signal Y of the amplifier 35 which has amplified the output signal Y is input to the sample hold circuit 38 via the switch SW, and the sample hold circuit 38 samples and holds the signal level of the output signal Y, and the amplifier It is amplified at 35 and a displacement signal S38 is output. As a result, the level of the output signal Y at the zero crossing point of the output signal S30, that is, the amplitude of the objective lens 15 is sampled. The sampled displacement signal S3
8 is input to the distance conversion unit 50, the displacement signal S38 is converted into a distance according to the displacement signal S38, and the displacement of the surface of the DUT 16 is measured.

FIG. 7 shows the output signal Y and the one-shot pulse S.
34 is a timing chart of 34 and a displacement signal S38.
As described above, when the output signal Y is changing corresponding to the position (amplitude) of the lens 15 as shown in FIG. When the one-shot pulse S34 shown in b) is generated, the level of the output signal Y at that time is sampled. Then, when the DUT 16 is moved in the direction orthogonal to the optical axis, the displacement signal S38 is changed according to the displacement of the surface of the DUT 16 shown in FIG.
As shown in (a), the displacement signal S38 changes in a stepwise manner.
And the displacement of the surface of the DUT 16 correspond to each other.
Therefore, if the level of the output signal Y is sampled, the displacement of the DUT 16 can be measured with high accuracy according to the level of the output signal Y.

Further, since the lens 15 is vibrated and the level of the output signal Y at the time when the in-focus point is generated is measured to measure the displacement of the surface of the DUT 16, the displacement is measured at high speed. it can.

FIG. 8 is a block diagram showing another configuration of the arithmetic unit 20. The output signal X is input to the peak detection circuit 40, the peak detection signal SP output from the peak detection circuit 40 is input to the first counter 41, and the count value is input to the arithmetic circuit 42. On the other hand, the output signal Y is input to the zero-cross detection circuit 43, and the zero-cross detection signal S0 that has detected the zero-cross is the first counter 41 and the second counter 41.
Of the counter 44. The count value of the counter 44 is input to the arithmetic circuit 42.

Then, the phase signal S42 which is the calculation result is outputted from the calculation circuit 42 and inputted to the distance conversion section 50. The counter 41 has a latch section,
The count value can be latched twice and the zero-cross detection signal S0
The count value is cleared by. The counter 44 is provided with a latch unit, which can latch the count value once, and the count value is cleared by the zero-cross detection signal S0.

Next, the operation of the displacement meter when using the arithmetic unit configured as described above will be described with reference to the output signal Y and the peak value detection signal S.
A timing chart of P and the zero-cross detection signal S0 will be described with reference to FIG. Now, when the output signal Y shown in FIG. 9A corresponding to the position (amplitude) of the lens is input to the zero-cross detection circuit 43, the zero-cross time point of the output signal Y is detected, and the zero-cross detection circuit 43 outputs the zero-cross detection time.
The zero-cross detection signal S0 shown in (c) is output. As a result, the count values of the counters 41 and 44 are cleared, and then the counters 41 and 44 start counting operation and count time. And the counter 44 is 1
2 from the time when the zero-cross detection signal S0 is given for the second time
The time until the time when the zero-cross detection signal S0 is applied for the second time, that is, the time t3 of one cycle of the output signal Y is counted, and the count value is latched by the latch unit.

On the other hand, when the output signal X obtained when the object 16 to be measured is focused is input to the peak detection circuit 40, the peak detection circuit 40 detects the peak value of the output signal X and the peak detection signal SP. Is output and input to the counter 41. As a result, the counter 41 causes the latch unit of the counter 41 to latch the count value t1 up to the time when the first peak detection signal SP is input. Further, the count value t2 up to the time when the second peak detection signal SP is input is latched by the latch unit of the counter 41. The count values t1, t2, t3 latched in this manner are used for the arithmetic circuit 4
Enter in 2. As a result, the arithmetic circuit 42 uses sin-1 (t1) based on the input count values t1, t2, t3.
/ T3) and sin-1 (t2 / t3) are calculated to calculate the phase of the output signal Y at the output time point of the peak detection signal SP.

The phase of the output signal Y calculated in this way corresponds to the level of the output signal Y when the object 16 to be measured is focused, that is, the position of the lens 15. Then, the phase signal S38 which is the calculation result is converted into
It is output from 2) and input to the distance conversion unit 50, converted into a distance and the displacement of the surface of the DUT 16 is measured. Even if the phase of the output signal Y at the time when the peak value of the output signal X is detected is obtained in this way, the displacement of the surface of the DUT 16 can be measured.

When the reflected light from the DUT 16 passes through the pinhole 17a and enters the photodiode 18, the spread of the light occurs at the light projection position of the DUT 16 due to the latent light or the stray light. However, only the strong light when the focal point is generated is incident on the photodiode 18, and the received light output of the photodiode 18 does not change due to the reflected light due to the latent light and the stray light. Can be measured without giving.

FIG. 10 is a block diagram of another conventional example of the vibrating section. Piezoelectric elements CM are fixed to the outer surface of the one-side long portion of the tuning fork 21 and the outer surface of the other-side long portion, and the tuning fork 21 can be vibrated by applying a voltage to the piezoelectric element CM. .

FIG. 11 is a block diagram of still another conventional example of the vibrating section. Peripheral portions of the lens 15 and the lens 14 are attached to the tips of the long side portions of the tuning fork 21. Both the lens 15 and the lens 14 can be vibrated. In this way, the weight between the elongated portions on one side of the tuning fork 21 can be balanced, and the tuning fork can be efficiently swung.

FIG. 12 is a block diagram of another conventional example of the optical diaphragm 17. The slit SLT is linearly opened with a predetermined length, and the opening width of the slit SLT is the pinhole 17
It is formed to have substantially the same size as the diameter of a. When such a slit SLT is used, the reflected light from the object to be measured slightly passes through and the light receiving performance of the light receiving unit is slightly deteriorated, but an assembly for allowing the specific reflected light from the object to be measured to pass therethrough. Position adjustment becomes easier.

Such a measurement error with respect to the sneaking-in light and the stray light is as shown in FIG.
Is arranged, and the size of the spot of the laser light irradiated to the object at the time of focusing is made small so that the underneath light and the stray light are not received by the light receiving section E and are eliminated.

[Problems to be Solved by the Invention]

However, even if the influences of the sneaking light and the stray light are eliminated in this way, when the displacement of the surface of the object 16 is measured through the translucent substance 50 as shown in FIG.
When the laser light passes through the transparent substance 50, the laser beam is refracted by this substance and an aberration occurs in the light flux. Therefore, it becomes impossible to converge the spot size of the laser beam to one point.

In FIG. 14, the wavy line shows the state in which the laser light is converged when there is no light-transmitting substance 50.
The solid line shows the state where the laser light is converged when the light-transmitting substance 50 is present. As can be seen from FIG. 14, when there is the light transmissive substance 50, the laser light cannot be converged to one point on the object 16 due to the aberration,
There is a problem that the measurement accuracy decreases.

In view of the above problems, the present invention provides a displacement gauge which can measure the displacement of the surface of an object through a translucent substance in the conventional displacement gauge which measures the displacement of the surface using a focusing point. An object of the present invention is to provide a displacement meter that accurately measures the displacement of a surface both when there is a translucent substance and when it does not.

[0036]

DISCLOSURE OF THE INVENTION The displacement gauge according to the present invention is
It has a lens for converging and projecting the light emitted by the light emitting unit to the object to be measured, and a light receiving section for receiving the reflected light from the object to be measured, and at least one of the lenses is moved substantially in the optical axis direction. The moving means is a vibrating means for vibrating the moving means with a predetermined amplitude. The reflected light is received by the light receiving section through the first optical diaphragm section, and the object to be measured is received based on the received light amount. A displacement meter for measuring the displacement of the surface, further comprising a second optical diaphragm section arranged in front of and behind the moved lens, a position detection section for detecting the position of the moved lens, and the position. It is characterized in that it is provided with means for capturing the detection position signal output by the detection portion at the maximum time of the amount of light received by the light receiving portion, and means for obtaining the displacement of the surface of the object to be measured based on the captured detection position signal. .

[0037]

In the present invention, when the lens for converging the emitted light is vibrated with a predetermined amplitude in the substantially optical axis direction, the distance between the vibrated lens and the object to be measured changes. When the lens and the object to be measured reach a predetermined distance, convergent light with an improved influence of aberration is projected through the lens vibrated with respect to the object to be measured and the second optical diaphragm section. At this time, the size of the spot is made small, and the focal point of the projected light is generated on the object to be measured through the translucent substance. The reflected light from the object to be measured is projected onto the first optical diaphragm section, and the reflected light generated on the object to be measured by the latent light and the stray light is blocked. Then, only the reflected light from the in-focus position where the in-focus occurs passes through the first optical diaphragm section, and the light receiving section receives the light, and the light receiving amount of the light receiving section becomes maximum. The position of the lens when the amount of received light is maximum corresponds to the distance from the reference position of the optical system to the object to be measured. The displacement of the surface of the measured object can be measured by moving the measured object in the direction orthogonal to the optical axis.

Furthermore, by making the second optical diaphragm part detachable or slidable, it is possible to realize a displacement meter which is not affected by aberrations both when a transparent substance is present and when it is not.

That is, when there is no translucent substance, NA
By increasing, the light spot converged to a smaller size can be projected onto the surface of the object to be measured. on the other hand,
When there is a light-transmitting substance, the NA is reduced by the second optical diaphragm, but the influence of aberration is suppressed and a small converged light spot can be projected onto the surface of the object to be measured, which deteriorates the measurement accuracy. Can be suppressed.

[0040]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 15 is a schematic configuration diagram of a displacement meter according to the present invention. In addition to the configuration of FIG. 4, a second light diaphragm 29 is arranged in front of the lens 15. The second optical diaphragm 29 is composed of a hole having a predetermined diameter, and is attached to another optical system so as to be slidable in the V direction. This hole can be moved and arranged on the optical axis of the laser when measuring the displacement of the surface of the object through a light-transmitting substance, and the light flux of the laser can be narrowed.

This hole has a diameter of, for example, about several millimeters, and is set to be smaller than the diameter of the light beam in the portion where the second optical diaphragm 29 is arranged, and preferably about half the diameter of the light beam. Is desirable.

As a result, of the light flux indicated by the solid line in FIG. 14, the laser light passing through the outer peripheral portion with respect to the optical axis and irradiating the object is eliminated, and the aberration of the laser light is the second. The size is smaller than that when the light diaphragm 29 is not provided. Therefore, it is possible to improve the measurement accuracy when measuring the displacement of the surface of the object through the translucent substance.

Further, as described above, the second optical diaphragm 2
Since 9 is slidably mounted, the displacement can be measured without lowering the measurement accuracy by retracting the second optical diaphragm 29 from the light flux including the optical axis when no translucent substance is present.

Further, although the second optical diaphragm 29 is arranged in front of the lens 15 in the embodiment, even if it is behind the lens 15, it is composed of a plurality of lenses in this embodiment. Therefore, it may be behind the lens 14. That is, when there are a plurality of lenses, the second optical diaphragm 29 may be arranged between the adjacent lenses.

Further, although the second optical diaphragm 29 is a hole in the embodiment, like the slit as the first optical diaphragm shown in FIG. 12, it has a width similar to the diameter of the hole. It may be a rectangular slit.

In addition, the second optical diaphragm 29 is slidable, but may be detachable.

[0047]

As described in detail above, according to the present invention,
In addition to the conventional displacement gauge, a second optical diaphragm is provided, and this optical diaphragm is arranged in front of or behind the lens, and is made slidable or detachable. Even in some cases, it is possible to accurately measure the displacement of the surface of the measuring object.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of a conventional displacement measuring method.

FIG. 2 is a waveform diagram of a signal indicating the amplitude of the lens A in FIG.

FIG. 3 is a graph showing a change in the amount of light received by a light receiving unit when a focused point occurs
7 is a waveform chart showing the relationship with the amplitude of the lens A. FIG.

FIG. 4 is a schematic configuration diagram of a conventional displacement meter.

FIG. 5 is a block diagram showing a configuration of a calculation unit.

FIG. 6 is a signal waveform of each part in the calculation part.

FIG. 7 is a timing chart of signals of respective parts in the arithmetic unit.

FIG. 8 is a block diagram showing another configuration of a calculation unit.

9 is a timing chart of signals of respective parts in the arithmetic unit shown in FIG.

FIG. 10 is a configuration diagram showing another conventional example of a vibrating section.

FIG. 11 is a configuration diagram showing another conventional example of a vibrating section.

FIG. 12 is a configuration diagram showing another conventional example of the first optical diaphragm section.

FIG. 13 is a schematic configuration diagram of a conventional non-contact displacement meter.

FIG. 14 is a schematic view for explaining the occurrence of aberration that occurs when measuring the displacement of the surface of an object through a translucent substance.

FIG. 15 is a schematic configuration diagram of a displacement meter according to the present invention.

[Explanation of symbols]

 12 laser diode 14, 15 lens 16 object to be measured 17 first optical diaphragm section 18 photodiode 20 arithmetic section 21 tuning fork 22 tuning fork amplitude detector 24 solenoid 29 second optical diaphragm section

Claims (8)

[Claims] 1. A lens having a lens for converging light emitted from a light emitting unit and projecting the light on an object to be measured, and a light receiving unit for receiving reflected light from the object to be measured. In a displacement meter that measures the displacement of the surface of the measured object based on
A moving unit that moves at least one of the lenses in the substantially optical axis direction, a position detecting unit that detects the position of the lens moved by the moving unit, and a light receiving unit that receives reflected light from the object to be measured. And a means for capturing the detection position signal output by the position detection unit at the maximum time of the amount of light received by the light receiving unit, and a detection position signal based on the captured detection position signal. A displacement meter, comprising: a means for determining the displacement of the surface of the object to be measured; and a second optical diaphragm portion arranged in front of or behind the lens. 2. The moving means is a vibrating means for vibrating the moved lens with a predetermined amplitude, and the vibrating means has a tuning fork connected to the moved lens and a solenoid or a piezoelectric for driving the tuning fork. The displacement meter according to claim 1, which is constituted by an element. 3. The displacement meter according to claim 2, wherein the movable lens is connected to one end and the other end of the tuning fork of the vibrating means. 4. The displacement meter according to claim 1, wherein the first optical diaphragm portion is formed by a pinhole or a slit. 5. The displacement meter according to claim 1, wherein the second optical diaphragm is formed by a hole or a slit. 6. The diameter of the hole or the width of the slit, which is the second optical diaphragm, is substantially half the diameter of the light beam at the position where the second optical diaphragm is arranged. The displacement meter according to claim 5. 7. The displacement gauge according to claim 1, further comprising a slide unit that slides the second optical diaphragm unit. 8. The displacement meter according to claim 1, wherein the second optical diaphragm portion is removable.