JPH041283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical rotational accuracy measuring device, and more particularly to a measuring device for measuring the dynamic whirling rotational accuracy of a rotating body with good roundness.

BACKGROUND ART Conventionally, non-contact probes of eddy current type or capacitance type have been used to measure dynamic rotation accuracy in rotating systems using precision machined parts such as metal workpieces. Furthermore, when the rotating body is made of non-metal, the above-mentioned type of probe cannot be used, so various methods have been proposed. For example, it is possible to apply the principle of minute distance measurement using an optical probe, but all of these methods are affected by the material and shape of the rotating body, such as metal surfaces, and optical probes are affected by the material and shape of the rotating body. There is an inconvenience that calibration becomes very difficult because it is directly influenced by reflectance.

On the other hand, when trying to measure dynamic rotational accuracy with a contact probe, the measurement values become unstable and reliability decreases due to probe wear or the measurement pressure having a greater effect on the measurement system. There are serious drawbacks.

The present invention eliminates the various drawbacks of the prior art as described above, and provides a non-contact type optical whirling rotation accuracy measuring device that is extremely little affected by the material of the rotating body, surface reflectance, processing conditions, etc. The purpose is to

In this invention, a measurement member is brought close to the outer periphery of a rotating body to form an appropriate opposing gap of, for example, 0.1 mm to 1 μm, and a spot light emitting light of a constant intensity is applied to the opposing gap to increase the width of the gap at a predetermined period. The peak value and pulse width of the pulse signal generated by the transmitted light are
Taking advantage of the fact that it has a close relationship with the opposing gap width, n of the frequency _s synchronized with the scanning period of the scanning light is
The present invention is characterized in that the gap width is related to the amplitude of the Fourier component of the harmonic, and the gap width is measured using the amount to measure the whirling rotation accuracy.

The present invention will be described in detail below with reference to illustrated embodiments. In the figure, the tip of a measuring member 2 on which a knife edge is formed, for example, is brought close to the outer periphery of a rotating body 1 rotating in the direction of the arrow, and a setting means such as a moving mechanism 3 is used to place the tip of the knife edge and the outer circumferential surface of the rotating body 1. For example, opposing gaps having opposing gap width λ of 0.1 mm to 1 μm are formed.

4 is a light projecting means such as a He-Ne laser oscillation tube, and the laser beam emitted from the oscillation tube 4 is narrowed to an appropriate beam spot diameter by a pinhole 5, and split into two directions by a beam splitter 6. .

The laser beam whose direction is changed at right angles by the beam splitter 6 is photoelectrically converted by the _Si solar cell 7, and is used for correction of intensity fluctuations of the laser beam, which will be described later.

The spot light traveling straight through the beam splitter 6 is made to enter a vibrating mirror 9 via a reflecting mirror 8. The vibrating mirror 9 is part of an oscillation circuit composed of an oscillator driver 10 and a tachometer generator (not shown) attached to the vibrating mirror 9, and is an optical scanning means that oscillates at the self-resonant frequency _s of the vibrating mirror 9. becomes. The spot light reflected from the vibrating mirror 9 becomes a fan-shaped scanning beam corresponding to the frequency _s , and is turned into a scanning light traveling in parallel by an objective lens 11 disposed in the optical path. That is, the position of the objective lens 11 is set to be equal to the focal length of the objective lens 11 itself with respect to the reflection point on the vibrating mirror 9.

Then, the opposing gap between the rotating body 1 and the measuring member 2 is irradiated with parallel scanning light (spot light) passing through the objective lens 11, and the width of the opposing gap is scanned. The spot light irradiates the opposing gap parallel to the axis of the rotating body 1.

The scanning light transmitted through the opposing gap is collected by a light receiving optical system 15 including condenser lenses 12a and 12b, an interference filter 13 provided to reduce the influence of external light, and a photomultiplier tube 14, and is photoelectron multiplied. Double tube 14
Photoelectric conversion is performed. The electrical signal from the photomultiplier tube 14 is amplified by a preamplifier 16 and then input to a lock-in amplifier 17 with an auto-phase function. The output signal of the oscillation driver 10 of the vibrating mirror 9 is input as a reference signal of the amplifier 17, and the output is input to the laser light intensity fluctuation correction unit 19 together with the output amplified by the amplifier 18 of the solar cell 7. Then, the correction section 19 outputs a voltage V that has a certain relationship with the facing gap width λ, as will be described later.

The laser light intensity fluctuation correction unit 19 is used to minimize the influence of fluctuations in laser light intensity caused by temperature and other factors.

In the above, the output voltage V is measured according to the relationship expressed by V = F (λ) or λ = F ^-1 (V) λ: opposing gap width,
The facing gap width λ can be measured indirectly. The specific form of the function F(λ) will be determined later.

In the above opposed gap width measurement, by rotating the rotating body 1, the gap change during rotation, or if the circularity of the rotating body 1 is sufficiently good, the gap change due to whirling during rotation can be accurately measured. can be measured. In the embodiment, the vibrating mirror 9
The vibration frequency was approximately 2kHz. Therefore, it could be used up to approximately 12,000 R.PM in terms of rotational speed.

Figure 3 shows the actually obtained signal waveform V after the photomultiplier tube output, but compared to the opposing gap width,
By setting the spot diameter of the laser beam to be considerably large, Vpeak becomes approximately proportional to the facing gap width λ. Further, the pulse duration Twidth is also a function of the facing gap width λ.

The relationship between the output voltage V and the facing gap width λ is expressed by the third
By performing Fourier analysis on the pulse train as shown in the figure, it is derived that the following relationship exists: V = K _p /πΔZSin2πΔZ where ΔZ = λ/Xo Xo: laser beam scanning width Ko: appropriate proportionality constant. In normal use, since λ≪xo, V and opposing clearance width λ
It can be seen that there is a simple quadratic relationship: V = k ₁ (Δz) ² k ₁ : an appropriate constant of proportionality.

In the above, the response speed of the photomultiplier tube 14 and preamplifier 16 depends on the pulse rise or 1/Twidth.
The discussion was about the case where the response speed of the photomultiplier tube 14 and the preamplifier 16 is relatively slow (the response frequency of the system is _R ), that is, Twidth≪1. / If _R holds, then
Twidth is no longer a function of the opposing gap width λ,
This results in a pulse with a constant width determined by the response speed of the system. In this case, the relationship between the output voltage V and the facing gap width λ is linear, and can be expressed as V = K ₂ ΔZ K ₂ : an appropriate proportionality constant.

The rotational accuracy is measured by applying the above measurement principle, but if you measure from the X and Y directions as shown in Figure 4, you can measure the rotational accuracy in a more specific way. It can be performed.

In other words, the optical scanning means is
The output voltage from each measuring section is input to the X and Y input sections of the oscilloscope, and a Lissage figure is drawn to obtain the amount of distortion from a perfect circle. Measure rotation accuracy. 9' is a reflecting mirror.

As described above, since this invention is a non-contact method using a laser beam or other suitable optical probe, there are no problems such as wear of the probe and variations and changes in measurement pressure as in the past. In measurement, the amount of light transmitted from the opposing gap between the outer periphery of the rotating body and the measuring member is used, so there is no effect of the material of the rotating body (however, transparent objects are excluded), and the surface It has various advantages such as very little influence on the reflectance and processing conditions, making it possible to measure with high precision.

[Brief explanation of drawings]

Fig. 1 is a system diagram of one embodiment of this invention, Fig. 2 is a side view of the main part, Fig. 3 is a waveform diagram of an electric signal obtained by photoelectric conversion, and Fig. 4 a and b are other embodiments. They are a front view and a side view of the main part of the example. DESCRIPTION OF SYMBOLS 1... Rotating body, 2... Measuring member, 3... Moving mechanism (setting means), 4... Light projecting means, 9... Vibrating mirror (light scanning means), 14... Photomultiplier tube, 1
5... Light receiving optical system, 17... Lock-in amplifier,
19... Light intensity fluctuation correction section, λ... Opposing gap width.

Claims (1)

[Scope of Claims] 1. A measuring member for forming a facing gap on the outer periphery of a rotating body, a setting means for moving the measuring member to appropriately set the width of the facing gap, and a light projector for irradiating spot light. means, a light scanning means for irradiating the opposing gap with a spot light emitting light of a constant intensity and scanning the opposing gap in the width direction of the gap at a predetermined period; and receiving the light transmitted through the opposing gap for photoelectric conversion. and a lock-in amplifier that receives the output pulse signal of the photoelectric conversion means, detects and outputs an n-th harmonic component of a frequency _s synchronized with the scanning period of the optical scanning means among its Fourier series components. An optical whirling rotational accuracy measuring device, characterized in that the whirling rotational accuracy of the rotating body is measured by the output voltage of a lock-in amplifier corresponding to the change in the opposing gap width between the rotating body and the measuring member. . 2. Two sets of setting means for arranging two measuring members with a phase difference of 90° around the outer periphery of the rotating body and moving each measuring member individually to form the opposing gaps, and each opposing gap. two sets of optical scanning means that scan each gap in the width direction with respective spot lights, two sets of photoelectric conversion means that individually receive the light transmitted through each opposing gap, and an output pulse signal of each photoelectric conversion means. of each Fourier series component, the frequency _s is tuned to the scanning period of the optical scanning means.
2. The optical whirling rotation accuracy measuring device according to claim 1, further comprising a lock-in amplifier that detects n-th harmonic components of and outputs voltages corresponding to the respective n-th harmonic components.