JPS6014106A - Method and device for measuring dimension - Google Patents

Abstract

PURPOSE:To improve the measurement precision by arranging a measuring member so that it faces a face to be measured of a cylindrical object with a proper gap between them and scanning this gap with a spot light and detecting a prescribed higher harmonic component of the optical signal transmitted through the gap. CONSTITUTION:A cylindrical object 1 to be measured is placed on an attaching base 2, and a measuring member 4 having a knife edge 3 faces the object 1 from above with a proper gap between them. The laser light emitted from a gas laser 8 as a light source scans the gap as a scanning beam through an oscillating mirror 12. The light transmitted through the gap is made incident to a photoelectric multiplier 7 through a light receiving optical system 6 and is converted to an electrical signal. This electrical signal is amplified in a preamplifier 18 and is inputted to a lock-in amplifier 19. The amplifier 19 detects and outputs a prescribed higher harmonic component out of Fourier series components of the electric signal. This output signal corresponds to the width of the gap, and dimensions of the outside diameter of the object 1 to be measured are calculated on a basis of this value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dimension measuring method and apparatus, and more particularly to an electro-optical dimension measuring method and apparatus suitable for an object to be measured having a cylindrical surface to be measured.

As a method to measure the outer diameter dimensions of rollers, shafts, etc.
There are methods in which the gauge is brought into direct contact with the surface to be measured, and methods in which it is not brought into contact.

An electric gauge method is known as a method of directly contacting the gauge, but surface scratches are likely to occur at the contact portion, resulting in a problem in repeatability.

As a non-contact method, there is an air gauge method, but its accuracy is rough and cannot measure, for example, on the submicron order.

On the other hand, laser length measuring machines that utilize interference fringes caused by laser light are known, but their adjustment is complicated and requires the installation of a reflector such as a corner cube.
It is not suitable for measuring minute parts.

This invention does not have the limitations of using interference fringes or the inconvenience that measurement accuracy is affected by the individual differences of the measurer, unlike the laser interferometer mentioned above, and can achieve high measurement accuracy. The purpose of this invention is to provide a method and device for measuring the dimensions of the object to be measured.
A measuring member is disposed with an appropriate opposing gap formed, the gap is scanned with a spot light, the light transmitted through the gap is photoelectrically converted, and a predetermined harmonic component of the Fourier series component of the output electric signal is detected. The present invention is characterized in that the dimensions of the object to be measured are measured based on the relationship established between the detected output and the gap width.

The present invention will be explained in detail below based on illustrated embodiments. The embodiments shown in FIGS. 1 to 4 show a case where, for example, the outer diameter of a roller of a needle roller bearing is measured.
A roller as an object to be measured 1 is placed on a mounting bracket 2 made of a block or the like, and a measuring member 4 having a knife 3 is opposed from above with an appropriate clearance width Δz4-. This facing gap width Δ2 is set to be larger than the variation in diameter (variation in circularity) of the object to be measured 1. Electric micro probe for position adjustment 5
etc. to the upper end of the measuring member 4 to set it at the optimum position.

The gap is scanned with a spot light such as a scanning laser beam from a direction perpendicular to a plane connecting the center of the object 1 to be measured and the knife 3 of the measuring member 4 in the opposing gap width Δ2, and this light scanning causes the gap to be The transmitted light enters a photomultiplier tube 7 through a light receiving optical system 6 consisting of a condensing lens 61L T 6 b, etc., and undergoes photoelectric conversion to obtain an electric signal corresponding to the intensity of the transmitted light. The actual clearance width Δz is determined based on the relationship established between the clearance width Δ2 and the clearance width Δ2.
l is calculated, and the outer diameter of the object to be measured 1 is measured based on the calculated value.

The spot light that scans the opposing gap between the object to be measured 1 and the knife 3 is a laser light whose light source is a He-Nθ gas laser 8, and the beam diameter is adjusted to an appropriate value by passing through a pinhole 9. Thin beam splitter
10 splits the light into two directions, and the light traveling straight is reflected by a reflecting mirror 11.
'jfc to the vibrating mirror 12. The vibrating mirror 12 is vibrated at a predetermined frequency fR, and uses the reflected light as a scanning beam to scan the opposing gap.

The spectrum obtained by changing the optical path at right angles with the beam splitter 10 is
The photodiode 13 performs photoelectric conversion, and the output thereof is provided as an output correction signal to be described later.

The direction of the laser beam reflected by the vibrating mirror 12 is changed by the vibrating mirror 12 within a predetermined fan-shaped angle range, but there is pressure between the vibrating mirror and the lens between the vibrating mirror 12 and the opposing gap. A lens 14 is provided, which is arranged to have a focal length equal to that of the entire self, so that the reflected light from the vibrating mirror 12 is perpendicular to the direction in which the object to be measured 1 and the knife blade 3 face each other (X-axis direction), and the gap is This is so that it is converted into a parallel scanning beam that scans the gap in a transverse direction (X-axis direction).

The vibrating mirror 12 forms part of an oscillation circuit including an attached tacho generator (not shown) and an oscillation driver 15, and vibrates at the self-resonant frequency f8 of the vibrating mirror 12.

The object to be measured 1 is placed on its mounting base 2, and if necessary, the slide base 16 is slid in the axial direction (X-axis direction) of the object to be measured 1 by a drive means (not shown) to define the opposing gap. Optical scanning is performed at the position.

In this case, in the embodiment, the knife 3' is fixed with respect to the lx-axis direction, but this is because the length of the knife 3 in the X-axis direction is set to be approximately the same length as the length of the object to be measured l. In such a case, a holding part (not shown) for holding the measuring member 4 may be provided on the slide base 16 so that the measuring member 4 can be moved in the same direction as the object to be measured. It is also possible to have a configuration in which the optical system and the knife are slid in the x-axis direction, and the optical system and the knife are slid and fixed in the x-axis direction.

Between the light receiving optical system 6 and the photomultiplier tube 7, there is a distance of 6.328 mm.
An interference filter 17 that transmits A-wavelength light is interposed to minimize the influence of external light entering from the surroundings.

The electrical signal output from the photomultiplier tube 7 is sent to the preamplifier 1.
After amplifying the signal waveform V as shown in Fig. 3 according to 8,
It is input to the lock-in amplifier 19 at the next stage.

The peak value Vpeak and the pulse width Vwidth of the signal waveform V in FIG. 3 are closely related to the opposing gap width Δ2. This relationship becomes remarkable when the beam diameter of the scanning light is made sufficiently large compared to the gap width Δ2, and in the case of this example, the opposing gap width Δ2 is 0.01 μm to 10 μm.
If the beam diameter of the scanning light is set to 0.2 to 0.5 m, all of the above conditions are fully satisfied.

The electrical signal amplified by the preamplifier 18 is input to the lock-in amplifier 19 at the next stage, and a predetermined harmonic component among the 7-Lier series components of the electrical pulse train is detected and output from the lock-in amplifier 19. (In the embodiment, the second harmonic is output.) The lock-in amplifier 19 also has a vibration frequency f of the vibration mirror 12 output from the oscillator driver 15.
A signal with a frequency twice that of 8 is input as a reference signal. Therefore, the output V out of the lock-in amplifier 19 corresponding to the optical scanning of the portion of the opposing gap width Δ2 is the gap width Δ2.
Between, vout=-! ΔZ sin 2 π/2・・・・・・
...(1) Ko: Has a constant relationship.

In the output correction section 20 at the next stage, the output Vout'i of the lock-in amplifier 19 is input, while the output of the photodiode 13 is amplified by the preamplifier 21 and input as an output correction signal, and the output of the He-Ne gas laser 8 is inputted. A variation in the output V out due to light intensity fluctuation is corrected based on the output correction signal.

As shown in the fourth figure, the object to be measured 1 is rotated as shown by the arrow in the figure by a drive device (not shown). is inputted by a potentiometer etc., and the output Vout of the output correction section 20 is inputted to Y-human power.
'iEnter. As a result, a recorded waveform as shown in FIG. 5 was obtained. That is, the output Vout of the lock-in amplifier 19
The opposing gap width Δz4 can be measured from (actually, the output of the output correction section 20).

In addition, as a result of dimension measurement being performed with extremely high precision in this way, the mounting condition of the object to be measured placed on the object to be measured mount 2 must be maintained in good condition. For this purpose, a piezoelectric element 2 is installed on the mounting base 2.
4 is attached, and the piezoelectric element 24 is driven via a signal generator 25 and an amplifier 26. In other words, at an appropriate frequency, the mounting base 2
It is possible to fully excite the object 1 to be measured on the mount 2 and improve reproducibility. In the embodiment shown in FIG. An example is shown in which the influence of dust, oil film, etc. is offset. That is, a window 2a that transmits light is provided in the mounting base 2', two measurement members 4, 4"ii are arranged facing each other on the diameter line in the vertical direction of the object to be measured, and each knife 3°3' At the same time, two sets of light receiving optical systems 6 scan the gap facing the
, 6', two sets of photomultiplier tubes (not shown) are arranged. Therefore, when the output from the upper opposed gap, the light receiving optical system, the photomultiplier tube, and the lock-in amplifier 'fr:VxzT is defined as ■2, the signal processing method is vl+■2'.
f: Created by the adder circuit and set to 9 Vout.

In other words, when minute dust gets caught between the object to be measured and the mounting base, the object to be measured will float slightly;
Due to this floating, the output v1 due to the upper transmitted light becomes smaller, but the output v2 due to the lower transmitted light becomes correspondingly larger. Measurement errors due to imperfections can be canceled out, and the errors can be minimized to enable online measurement.

In each of the above embodiments, the outer diameter of a cylindrical object such as a needle roller is measured.
As shown in the figure, it is also possible to measure the inner diameter of an annular object to be measured IA having a cylindrical inner diameter surface.In this case, instead of using a knife as the measuring member, A ball 3Affi with a known diameter is used to form a minute opposing gap. As is clear from the figure, the measurement method is exactly the same as in each of the above-mentioned embodiments, and when considering the influence of minute dust etc., as shown in Fig. 8, the measurement method is In each of the above embodiments, it is advantageous in terms of measurement accuracy to use laser light as the scanning light, but it is not always necessary to use such coherent light. There isn't.

As described above, the present invention can measure the dimensions of objects to be measured, especially those having cylindrical surfaces to be measured, with extremely high accuracy.
It was confirmed that it is possible to measure the gap between the

[Brief explanation of the drawing]

Figure 1 is a system diagram of an embodiment of this invention, Figure 2 (a)
, (b) is a front view and side view showing an enlarged view of the opposing gap, FIG. 3 is a waveform diagram of an electric signal obtained by photoelectric conversion,
Fig. 4 is a front view of the main parts of another embodiment, Fig. 5 is a characteristic diagram obtained from the relationship between the optical scanning position and the lock-in amplifier output direction, and Fig. 6 is a characteristic diagram obtained from the relationship between the optical scanning position and the lock-in amplifier output direction.
Figures (a), (b), Figure 7 (a), (b)i
d Front view and side view of main parts of other embodiments, Fig. 8 (
a) and (b) are a front view and a plan view of still another embodiment. 1, IA...Object to be measured, 2, 2'...Mounting base, 3,
3'... Naifetsuji, 3A... Ball, j+4'
...Measurement member, 6, 6'... Light receiving optical system, 7...
Photomultiplier tube, 8...Hθ-Ne gas laser, 9.
...Pinball, 1゜...Beam splitter-112
... Vibrating mirror, 14... Lens, 16... Slide base, 19°° lock-in amplifier, 2o... Output correction section, 22... x-y recorder, Δ2... - Opposing clearance width Applicant Koyo Seiko Co., Ltd. Figure 1 Figure 2 (Q) (b) ↑ Figure 3 Figure 4 Figure 1 Same entry (θ) → Figure 7 (a) (b) Figure 8 ( 0) (b)

Claims (1)

[Scope of Claims] (1) A process of setting the measuring member so as to form a facing gap between the object to be measured and the measuring member that is larger than the variation in the dimensions of the object to be measured, and a process of setting the measuring member so as to form a facing gap between the object to be measured and the measuring member, and determining the gap by a spot light. An optical scanning process of scanning the period, a photoelectric conversion process of photoelectrically converting the source metal that passes through the gap by optical scanning, and a detection of a predetermined harmonic component among the two IJ series components of the electrical signal obtained by the photoelectric conversion. A dimension measuring method characterized in that the dimensions of the object to be measured are measured based on the relationship established between the detection output and the gap width (2) a mounting stand for the object to be measured, and a step on the mounting stand; a measuring member that forms an appropriate gap facing the object to be measured; a light projection device that irradiates a spot light; a light scanning device that irradiates the gap with a spot light and scans the gap at a predetermined period; a lock-in amplifier that receives an output electric signal from the photoelectric conversion means and detects a predetermined harmonic component among the Fourier series components of the electric signal; (3) The object to be measured has a cylindrical outer diameter surface to be measured, and the measuring member has an appropriate clearance on the outer diameter surface. (4) The dimension measuring device according to claim (2), which has knife blades that are opposed to each other. (5) The measuring member is formed so as to form the gaps at two locations on the diameter line of the object to be measured; Claim (2) in which two sets of optical scanning means and photoelectric conversion means are provided corresponding to each of the opposing gaps, and the output electric signals of the two sets of photoelectric conversion means are input to nine lock-in amplifiers and summed. The dimension measuring device according to any one of (4) to