JPH0242403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical shape measuring device, particularly a device for measuring the shape of a crowned surface of a rotating body such as a cylindrical roller or tapered roller, or other object that has been subjected to crowning. Regarding.

An enlarged projection method is a conventional method for measuring the external shape of precision machined parts such as metal workpieces. In this method, the image of the object to be measured projected onto a screen by a magnifying projector is superimposed on a type of figure gauge that shows the ideal external shape of the object to be measured, and the degree of agreement is measured. Improvement is mainly achieved by increasing the magnification ratio, but there is a limit to the magnification ratio due to reasons such as blurring of the projected image due to the phenomenon of diffraction of light from the edge of the object to be measured, or constraints on the screen area. Furthermore, since the degree of coincidence between the projected image and the figure gauge is usually measured by eye, it is extremely difficult to quantitatively measure the degree of coincidence, which is a major factor in reducing accuracy.

On the other hand, in recent years, X-Y tables, linear
Although technologies such as reading coordinates using an encoder and arithmetic processing using a computer are used in combination, the accuracy of reading the coordinates still largely depends on the individuality of the measurer.

The present invention provides an optical shape measuring device that achieves high measurement accuracy without restrictions on increasing the magnification rate or variations in measurement accuracy due to individual differences in measurers as in the case of the enlarged projection method. The purpose is to

In this invention, a reference gauge having a knife-edge straight edge is brought into contact with the external surface of the object to be measured, such as the roller, and the contact portion is irradiated with a laser beam or other appropriate light source. The spot light is scanned in the contact direction, and the scanning position is sequentially moved, for example, in the axial direction of the object to be measured, and the scanning light transmitted through the contact portion is photoelectrically converted, and its Fourier series components are A lock-in amplifier detects and outputs a predetermined harmonic component, and the lock-in amplifier output corresponding to each scanning position is recorded and read on an X-Y recorder or the like.

The present invention will be described in detail below with reference to the illustrated embodiments. The drawings show a case where the crowning shape of the crowned outer surface (cylindrical surface) of a cylindrical roller is measured.

With respect to the crowned outer surface 1a of the cylindrical roller 1 that is the object to be measured, the straight edge 2a of the reference gauge 2 whose lower end edge is a knife-edge straight edge 2a is parallel to the axis of the cylindrical roller 1. The cylindrical rollers 1 are arranged in such a way that they face each other, and the axial direction (X
axis) in the opposite direction (Z axis) perpendicular to the X axis.
(axis) with a spot light projected from a direction perpendicular to both the X and Z axes, and the light transmitted through the contact portion by this light scanning is sent to the light receiving system 3 consisting of condensing lenses 3a and 3b. The focused light is incident on the photomultiplier tube 4, photoelectrically converted to obtain an electrical signal corresponding to the transmitted light intensity, and scanning is performed based on the relationship established between this electrical signal and the gap width ΔZ of the contact part. The actual gap width ΔZ of the contact portion corresponding to the position is calculated, and the crowning shape is measured accordingly.

The spot light that scans the gap between the contact parts is
The laser light is from a He-Ne gas laser 5 as a light source. After the beam diameter is appropriately narrowed through a pinhole 6, the beam is split into two directions by a beam splitter 7, and the straight spot light is reflected by a reflecting mirror 8.
The beam is made incident on the vibrating mirror 9 via the oscillating mirror 9.

The vibrating mirror 9 forms part of an oscillation circuit including an attached tacho generator (not shown) and an oscillation driver 12, and vibrates at the self-resonant frequency f _c of the vibrating mirror 9.

The spot light reflected by the vibrating mirror 9 changes its reflection direction within a predetermined fan-shaped angle range due to the oscillation of the vibrating mirror 9. A lens 11 whose distance between the lenses is equal to its own focal length.
is placed and converted into a parallel scanning beam perpendicular to the scanning direction (Z-axis).

The beam splitter 7 changes the optical path at right angles, and the spectral light is photoelectrically converted by a photodiode 10 or the like, and its output is used as a correction signal to be described later.

The electric micro probe 13 for adjusting the setting position is pressed against the rear end (the upper end in the figure) of the reference gauge 2 which is placed in contact with the external surface of the cylindrical roller 1 placed on the measuring object mounting base 21. The reference gauge 2 is matched against the cylindrical roller 1 at the optimum position. Then, the one-way slide base 14 on which the measurement object mounting base 21, the reference gauge 2, and the electric micro-probe 13 are assembled is moved (slided) in the X-axis direction by a drive means (not shown), and the Perform optical scanning over the measurement area.

There is a distance of 6328 Å between the light receiving system 3 and the photomultiplier tube 4.
An interference filter 15 that transmits wavelength light is interposed,
Efforts are made to minimize the effects of outside light coming in from the surrounding area.

The electrical signal output from the photomultiplier tube 4 is converted into a signal waveform V as shown in FIG. 3 by the preamplifier 16.
The signal is amplified and input to the lock-in amplifier 17 at the next stage.

The peak value Vpeak and pulse width Vwidth of the signal waveform V are closely related to the clearance width ΔZ of the contact portion. This relationship becomes more apparent when the beam diameter of the scanning light is made sufficiently larger than the gap width ΔZ of the contact portion. Therefore, in the case of the embodiment, the beam diameter is made sufficiently large relative to the gap width ΔZ of the contact portion, so that the above-mentioned conditions are fully satisfied.

The lock-in amplifier 17 detects and outputs a predetermined harmonic component of the Fourier series components of the input electrical signal. In other words, the lock-in amplifier 17
In addition to the electrical signal, the oscillator driver 12
2 of the oscillation frequency f _c of the vibrating mirror 9 output from
A signal with twice the frequency is input as a reference signal. Therefore, the output Vout of the lock-in amplifier 17 corresponding to optical scanning with the gap width ΔZ has the following relationship with the gap width ΔZ: Vout=K ₀ /πΔZsin2πΔZ (1).

In the output correction section 18 at the next stage, the output Vout of the lock-in amplifier 17 is inputted, while the output signal of the photodiode 10 is inputted as an output correction signal, and the output correction unit 18 inputs the output signal of the photodiode 10 as an output correction signal. Correct the variation in output Vout.

The X-Y recorder 19 inputs the output Vout corrected by the output correction section 18 as a Y-axis signal, while
By inputting the output of the linear potentiometer 20 that is linked to the movement of the slide base 14 in the X-axis direction as an X-axis signal, and taking these as the X-axis and Y-axis in FIG. 4, the output characteristics as shown in the figure can be obtained. Get the graph.

The X-axis signal (corresponding to the amount of movement of the slide base 14) is transmitted from the linear potentiometer 20 described above.
Not limited to linear encoders, rotary encoders,
It may also be generated using an encoder or the like.

When the gap width ΔZ is minute as in this measurement system, the relational expression sin2πΔZ/2πΔZ=1 holds approximately, so the above equation (1) is generally Vout=K ₁ (ΔZ) ² ...(2 ) However, K ₁ ; can be replaced with a constant.

However, the electrical signal input to the lock-in amplifier 17 is transmitted through the photomultiplier tube 4 and the preamplifier 16.
By lowering the response speed of , the pulse width can be made constant regardless of the clearance width ΔZ, so under these conditions, the above equation (2) becomes Vout=K ₂ ΔZ ……( 3) However, K ₂ ; can be replaced with a constant. In other words, lock-in amplifier 1
The gap width ΔZ can be measured from the output Vout of No. 7 (actually, the output taken out from the output correction section 18).

It should be noted that if a laser beam is used as the scanning light as in the embodiment, it is advantageous in terms of measurement accuracy, but it goes without saying that the scanning light is not necessarily limited to such coherent light.

As described above, the present invention measures the clearance width of the contact portion of the outer diameter surface of the object to be measured with respect to the reference gauge over the entire area in the axial direction (X-axis direction). It is now possible to measure crowning shapes applied to objects etc. with extremely high accuracy, and unlike conventional magnification projection methods, measurement accuracy may vary due to individual differences, or there may be limits to accuracy due to restrictions on magnification. There will be no inconvenience.

In addition, a photomultiplier tube is used for photoelectric conversion of the light transmitted through the gap between the opposing parts, and a lock-in amplifier is used for detection processing, making it possible to further improve measurement accuracy.

[Brief explanation of drawings]

Fig. 1 is a system diagram of the embodiment, Fig. 2 a and b are front and side views showing enlarged contact parts, Fig. 3 is a waveform diagram of the electrical signal obtained by photoelectric conversion, Fig. 4 is a graph illustrating measurement results. 1... Cylindrical roller (object to be measured), 2... Reference gauge, 3... Light receiving system, 4... Photomultiplier tube, 5...
He-Ne gas laser, 9... vibrating mirror, 14
...Slide base, 17...Lock-in amplifier,
18...Output correction section, 19...X-Y recorder, 2
0... Linear potentiometer, 21... Measured object mounting base, ΔZ... Clearance width of opposing part.

Claims (1)

[Scope of Claims] 1. An object to be measured mount, and an orientation in which the edge thereof is orthogonal to the direction of contact with the object to be measured, and the edge thereof is in contact with the outer surface of the object to be measured attached to the mount to be measured. a reference gauge formed on a straight edge extending to the reference gauge, a light projecting means for irradiating spot light, and a light scanning means for scanning the contact portion between the object to be measured and the reference gauge with the spot light in the direction of the contact at a predetermined period. a light scanning position changing means for sequentially moving the light scanning position in a direction perpendicular to the scanning direction; a photomultiplier tube that receives and photoelectrically converts the light transmitted through the contact portion; A lock-in amplifier that receives an output electrical signal, detects and outputs a predetermined harmonic component of its Fourier series component, and a measurement value that reads the output of the lock-in amplifier in correspondence to each optical scanning position of the contact part. An optical shape measuring device comprising a recording means. 2. The optical shape measuring device according to claim 1, wherein the object to be measured is a rotating body such as a cylindrical roller or a tapered roller whose outer shape is crowned. 3. The optical shape measuring device according to claim 1 or 2, wherein the straight edge of the reference gauge is formed in a knife edge shape. 4. The optical shape measuring device according to claim 1, wherein the optical scanning position changing means moves the object to be measured and the reference gauge simultaneously in a direction perpendicular to the scanning direction.