JPH0771946A - Method and device for sensing surface roughness - Google Patents

Abstract

PURPOSE:To perform measuring and sensing operations during machining by applying a light-modulated signal to the surface of a target workpiece, and inputting to a computer a demodulated signal obtained by the phase shaping of the signal reflected, and continuing surveillance until change in the value of roughness reaches a certain value. CONSTITUTION:An oscillating signal generated by a signal generator is phase- shaped and fed to a modulator circuit. The phase-shaped signal is inputted to a personal computer PC via an A/D converter. Also, a light-modulated signal is applied to the surface of a workpiece and its reflected light is received by a photodiode, whose light reception signal is then demodulated into an electric signal by a demodulator circuit. This demodulated signal is fed to the personal computer PC via a second A/D converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting surface roughness and its apparatus, and in particular, the surface roughness of a metal part or member is continuously monitored during polishing or cutting to obtain a desired constant roughness. The present invention relates to a method and an apparatus for detecting the arrival at a threshold value.

[0002]

BACKGROUND OF THE INVENTION Generally, there are a contact type using a needle and a non-contact type using light as a method for measuring the roughness of surface processing, and at present, protection or measurement of a surface to be measured is performed. There is an increasing demand for in-process measurement that can be performed during processing because it is non-contact from the standpoint of speed and ease of measurement.

As the non-contact type, there are a typical optical stylus method, a light scattering method, an optical interferometry method, etc., and the outline thereof is as shown in FIG. Light) to the surface of the object to be measured through the optical component (lens), and the reflected light is received by the light receiver (photodiode) through the optical component (condensing lens). The data of the received light signal is calculated by a processing system (computer) to obtain a reflection characteristic (scattering characteristic), so that the roughness shape (roughness value) is indirectly (probably) known.

[0004]

However, according to the roughness measuring method of the non-contact type light scattering method using the above-mentioned general light (laser), the so-called ultra-precision, that is, When the amplitude (height difference of roughness) and the spatial wavelength (waveform wavelength of roughness) of the surface shape are much smaller than the wavelength of the laser, a sufficiently reliable data value can be obtained. When the amplitudes become close to the same, the scattered value of the reflected light becomes random and it becomes difficult to obtain a reliable data value. Further, the conventional device requires a complicated calculation, etc., so that the price of the device is soared and a sophisticated optical system system is required.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems, and by solving such problems, ordinary precision finishing (when the amplitude of the surface shape is equal to or larger than the laser wavelength) ) Can be measured and detected during processing, and the processing up to the planned value can be performed smoothly, and the permeability of the oil film on the surface of the workpiece can be increased, and the device price is low and operability is also high. It is an object of the present invention to provide a method for detecting surface roughness and a device therefor which are favorable.

[0006]

In order to achieve this object, a surface roughness detecting method and apparatus according to the present invention include:
The oscillation signal electrically obtained by the signal generator is subjected to phase shaping to generate a wave packet signal having a spectral width, which is optically modulated, the surface of the target work is irradiated with this optically modulated signal, and the reflected signal is received by the light receiving means. The signal is demodulated to an electric signal to be phase-synchronized, and the phase-shaped signal and the demodulated signal are input to a computer through an analog-digital converter to continuously change the roughness value of the target work. To monitor until reaching the value and multiple oscillators,
A light source electric circuit section having at least an adder, and a light emitting section for an optical signal of a wave packet generated by the light source electric circuit section,
A light receiving part for reflected light of the optical signal, and a computer for inputting an electric signal before and after demodulation to the optical signal and monitoring a light scattering characteristic. It has a feature.

[0007]

With this structure, while processing the workpiece, the processed surface is irradiated with a wave packet, that is, a laser having a plurality of wavelengths superposed, and the wavelength of which is pseudo long. In comparison with the surface amplitude and surface roughness spatial wavelength, it can be approximated to the measurement on an ultra-precision surface with a surface amplitude smaller than a single laser wavelength. The measurement can be theoretically analyzed. Also, if the wave packet is continuously irradiated to the surface of the workpiece being machined, and if the machining progresses to the expected roughness value by monitoring the change in roughness value,
At that point, control for stopping the processing can be performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will now be described with reference to FIGS. FIG. 1 is a block diagram of a surface roughness detecting device embodying the present invention, FIG. 2 is a circuit block diagram of the light source section, FIG. 3 is a waveform diagram of a single sine wave and a wave packet wave showing oil film permeability, and FIG. FIG. 5 is a graph showing short-wavelength wavepackets and long-wavelength wavepackets, showing a surface roughness measurement result by wavepacket waves, and FIG. 5 is a waveform diagram showing a procedure of forming wavepacket waves.

First, in FIG. 1, 1 is a signal generator, that is, an oscillator composed of an electric circuit. The oscillation signal generated by the signal generator 1 is phase-shaped and sent to the modulation circuit 2. Up to the modulation circuit 2, it is a so-called time-oscillation wave in an electric signal state. The phase-shaped signal is input to the personal computer 4 via the first analog-digital converter 3.

Further, a light-modulated signal (which becomes a wave-pack wave as described later) is applied to the surface of the work, and the reflected light is received (photodetected) by a photodiode, and the received signal is demodulated by the demodulation circuit 5. Demodulate to an electric signal. This demodulated signal is phase-synchronized (see the change in voltage value), but at the same time, it is sent to the personal computer 4 via the second analog-digital converter 6. That is, the surface finish status is made visible on the screen as an electric signal (analysis by an analyzer).

The above is an outline of the detection apparatus. Here, the light source section for generating an optical signal for irradiating the surface of the work will be described. As shown in FIG. 2, a plurality of oscillators are prepared and different from each other. A wavelength oscillating signal is generated. Each of these oscillation signals is converted into a wave packet signal by the adder via the variable resistor, and emitted from the LED via the driver. Since this light emission uses a light modulation method, an infrared light emitting diode is used, and a pin photodiode is used as a light receiving element.

FIG. 3 shows waveforms (test results) when a sine wave signal is used as an input signal (A) and when a wave packet signal is used (B). (1) corresponding to each of (A) and (B) is an input waveform, (2) is a reflected waveform with an oil film, and (3) is a reflected waveform without an oil film. The cutting oil used here was spindle oil type 2, No. 3, irradiation light was vertically incident, and the surface was 0.2S lap finish.
From the comparison of the reflected waveforms in this figure, in (A), the waveform amplitude in the case with the oil film (2) is smaller than that in the case without the oil film (3),
Since the difference is not significant in (B), it can be seen that the wave packet has less attenuation of reflected light and is superior in oil film permeability.

Further, FIG. 4 shows the result of the surface roughness judgment (measurement) by the wave packet. The white dots in the graph indicate no oil film,
(A) shows the short wavelength of the wave packet generated by changing the spectral width of the input electric signal when the black dot is the oil film,
(B) shows the case of irradiation light with a long wavelength, and the scattered light intensity is shown with respect to the roughness value (center line average roughness Ra). When the surface roughness is small, (A) However, it can be seen that when (B) is large, the scattered light intensity changes greatly (arrow in the figure). This means that the scattering characteristics change when the wave packet corresponding to the frequency of the shape is irradiated, and by setting the expected accuracy of the surface roughness value here and making it correspond, the finishing degree of the workpiece surface during machining can be improved. It will be possible to detect and monitor.

A plurality of types of sine waves are oscillated and generated as described above, but as shown in FIG. 5, for example, when the sine waves of A and B are overlapped, the state becomes C, and the wavelength λ _{3 of the} envelope shown by D is It acts as the wavelength of the wave packet, and the wavelength λ ₃ of this wave packet can be generated corresponding to the amplitude of the surface roughness value to be planned.

The surface roughness detecting method and apparatus according to the present embodiment are configured as described above. Conventionally, lasers can be used to measure roughness values for ultra-precision finishing because the spatial distribution of scattered light directly corresponds to the power spectral density of surface fine shapes in the region where the amplitude of the irradiation surface shape is extremely smaller than the wavelength of the laser. This is because the roughness value can be evaluated from the integrated value of light. In contrast to this theory, a wave packet wave is transmitted and the amplitude of the irradiation surface shape and the wavelength of the wave packet wave are substantially the same, or the irradiation surface shape is The theory in ultra-precision finishing can be applied approximately by creating a region (precision finishing region) smaller than the (light) wavelength.

In other words, the theory in ultra-precision finishing is that when a wave packet close to a plane wave is created in a certain area on a certain surface and the analysis amount of the wave is considered as an integral amount, the amplitude distribution on the image plane from the surface is the Fourier distribution of the surface shape. It becomes a conversion. Then, since the Fourier coefficient corresponds to the spatial frequency of the shape, the shape of the surface roughness correlates with the intensity distribution of the image. Specifically, the one obtained by integrating the above amplitude distribution in the spatial frequency band is
It is believed to give Rq (root mean square roughness) in that bandwidth. Therefore, if a wave packet with a length Δ to 2π / Δk is created with a small wave number Δk, the light modulation wave has a wavelength larger than originally, and the roughness measurement theory of ultra-precision finishing uses a more rough value. It can be applied approximately even in a large region of.

[0017]

The method and apparatus for detecting surface roughness according to the present invention are constructed as described above. Therefore, a reliable measured value can be obtained by light even in a normal precision finish or in a region where the roughness value is larger, and the wavelength of the wave packet is selected and generated according to the expected roughness value and continued. It is possible to detect that the roughness value has been reached by performing a dynamic monitoring, and it is not necessary to continue unnecessary processing or to measure again. In addition, the structure can be made cheaper than the conventional one, and the oil film permeability of the signal wave in the measurement during processing is greatly improved, which is practical.

[Brief description of drawings]

FIG. 1 is a block diagram of a surface roughness detection device embodying the present invention.

FIG. 2 is a circuit block diagram of a light source unit.

FIG. 3 is a waveform diagram showing the oil permeability, (A) is a single sine wave, and (B) is a wave packet wave diagram.

FIG. 4 is a graph showing a surface roughness measurement result by a wave packet, where (A) is a short wavelength wave packet and (B) is a long wavelength wave packet.

FIG. 5 is a waveform diagram illustrating generation of a wave packet.

FIG. 6 is a block diagram of a general non-contact type surface roughness measuring mechanism.

[Explanation of symbols]

 1 signal generator 2 modulation circuit 3 first analog-digital converter 4 personal computer 5 demodulation circuit 6 second analog-digital converter

Claims (2)

[Claims] 1. An oscillation signal electrically obtained by a signal generator is subjected to phase shaping to generate a wave packet signal having a spectral width and is optically modulated, and the optically modulated signal is applied to the surface of a target work. The reflected signal is received by the light receiving means and demodulated into an electric signal for phase synchronization, and the phase-shaped signal and the demodulated signal are input to the computer through the analog-digital converter to continuously obtain the roughness of the target work. A method for detecting surface roughness, characterized in that the change in the value is monitored until it reaches a certain value. 2. A light source electric circuit section having at least a plurality of oscillators and an adder, a light emitting section for an optical signal of a wave packet generated by the light source electric circuit section, and a light receiving section for reflected light of the optical signal. And a computer for inputting an electric signal before and after demodulation to the above-mentioned optical signal and monitoring a light scattering characteristic.