JPH01284742A - Surface defect detecting device - Google Patents

Abstract

PURPOSE:To accurately detect a defect part in the surface of a body to be inspected by setting the distance between an end surface part of a reflection type optical fiber sensor and the surface of the body to be inspected within such a range that the output characteristics of the reflection type optical fiber sensor are saturated to enter a peak area. CONSTITUTION:Light from a projection lamp 34 in the reflection type optical fiber sensor 3 is projected on the surface of a roller component 1 which is rotated from a head part 33 through a projection optical fiber 31. Reflected light from the surface of the roller component 1 is projected on a photodetector through a photodetection fiber 32 and converted photoelectrically. In this case, if there is a defect such as a projection or recess in the surface of the roller component 1, the output signal of a photodetector 35 varies in level, which is judged by a processing part 36 to detect the defect position. Since the distance between the roller component 1 and head part 33 is set initially to the center value of the distance range corresponding to the saturation peak area of the output characteristics of the reflection type optical fiber 3, an error based upon shape accuracy is eliminated and accurate detection is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a surface defect detection device, and in particular, a reflective optical fiber sensor integrally equipped with a light emitting fiber and a light receiving fiber. The present invention relates to a surface defect detection device that optically detects defects formed on surfaces.

(Prior Art) In recent years, a light reflection type surface defect detection device that detects defects formed on the surface of a cylindrical roller part in a non-contact manner has been developed and is being widely used. This light reflection type surface defect detection device uses a reflection type optical fiber sensor that is integrally equipped with a light emitting fiber and a light receiving fiber. The tip end surface of this reflective optical fiber sensor is placed close to and facing the surface of the roller part, which is the object to be inspected, so that the scattered intensity of reflected light can be detected.

For example, in a cylindrical object surface inspection apparatus described in Japanese Patent Application Laid-Open No. 57-124205, a reflective optical fiber sensor integrally equipped with a light emitting fiber and a light receiving fiber is used to inspect the surface of a cylindrical object, which is the object to be inspected. It is used as a function of the distance to the cylindrical object, and the unevenness of the surface of the cylindrical object is emphasized and output as an electric signal according to frequency. In the reflective optical fiber sensor in this conventional device, a light receiving fiber is arranged in the center part, and a light emitting fiber is arranged in the outer peripheral part. A configuration is adopted in which the distance between the reflective optical fiber sensor and the surface of the object to be inspected is a function. That is, FIG. 8 shows the output characteristic curve of the reflective optical fiber sensor with respect to the above-mentioned distance, and among the characteristic curves shown in this figure, the slope region where the characteristic value fluctuates greatly is used, so that the sensitivity with respect to the above-mentioned distance is sensitive. It is made so that.

However, in such conventional devices, as mentioned above, the output sensitivity is a function of the distance between the end face of the reflective optical fiber inser and the surface of the cylindrical object to be inspected, and therefore, for example, If the above-mentioned distance changes due to the shape accuracy of the object to be inspected, such as eccentricity, this is detected as an error, which poses a problem. In addition, when using the device using the region where the output characteristic curve of the reflective optical fiber sensor shown in FIG. 8 monotonically decreases, the distance from the cylindrical object surface will be large; There is a problem in that in order to increase the scattering intensity of light, only cylindrical objects with small surface roughness, such as mirror surfaces, can be inspected.

In order to increase the intensity of light scattering, measures such as bringing the end face of the optical fiber sensor closer to the surface of the object to be inspected, amplifying the output signal from the receiving fiber, and increasing the amount of light from the transmitting fiber are available. However, the S/N ratio is poor in both cases. If processing such as applying a filter to the output signal is performed to improve the S/N ratio, there is a problem in that it takes a long processing time to detect the output and output it.

(Purpose) Therefore, an object of the present invention is to provide a surface defect detection device that can accurately and quickly detect defects formed on the surface of an object to be inspected with a simple structure. .

(Structure) In order to achieve the above object, the present invention provides a reflective optical fiber sensor having a reflective optical fiber sensor integrally equipped with a light emitting fiber and a light receiving fiber. In a surface defect detection device that optically detects a defect formed on the surface of an object to be inspected, the distance between the tip end of the reflective optical fiber sensor and the surface of the object to be inspected is It has a configuration in which the output characteristic value of the reflective optical fiber sensor with respect to the distance is set in a range corresponding to a peak region where it is saturated.

In a device with such a configuration, the intensity of light scattering from the surface of the object to be inspected is detected using the saturation peak region where the output of the reflective optical fiber sensor is stable. Even if the distance between the sensor and the surface of the object to be inspected varies, the output variation based on the variation is canceled and detection is performed.

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIGS. 1 and 2, a roller part 1 as an object to be inspected is supported in a substantially horizontal state by a holding mechanism (not shown), and is rotated in a fixed direction by a motor 2. It has become. A reflective optical fiber sensor 3 is installed close to the outer peripheral surface of the roller part 1. This reflective optical fiber sensor 3 is reciprocated in the axial direction of the roller part 1 by a motor (not shown). The rotational drive operation of the roller part 1 and the control operation of the reciprocating movement of the reflective optical fiber sensor 3 are executed based on signals from the control section 4.

The reflective optical fiber sensor 3 is integrally equipped with a plurality of light emitting fibers 31 and light receiving fibers 32, and has a head portion 33 provided at the tip thereof.
are arranged close to and opposite to the surface of the roller part 1.

The light emitting fiber 31 and the light receiving fiber 32 are
The base portions are separated from each other by the groove, and a floodlight lamp 34 as a light source and a photodetector 35 as a photoelectric conversion element are respectively installed so as to face each end face portion.

The output from the photodetector 35 is received by a processing section 36 including various detection circuits, and a display signal emitted from the processing section 36 is received by a display section 37.

As shown in FIG. 3, the head section 33 is divided into two parts, and in each divided area, end surfaces of a plurality of light emitting fibers 31 and light receiving fibers 32 are arranged in parallel in rows. The rows of end faces of the light emitting fibers 31 and the light receiving fibers 32 are arranged so as to extend in the axial direction of the roller part 1.

Here, the distance (gap amount) between the roller part 1 and the head part 33 is the reflective optical fiber sensor 3.
The output characteristics are set in a range where the output characteristics are saturated and reach the peak region. That is, in the output characteristic curve (described in detail later) of the reflective optical fiber sensor 3 in this embodiment shown in FIG. 4, the range of the distance (gap amount) corresponding to the peak region where the output characteristic value is saturated is t. The distance between the roller part 1 and the head part 33 is initially set to the median value T.

The detection operation in such an embodiment will be explained.

First, the floodlight 34 inside the reflective optical fiber sensor 3
The light emitted from the head part 33 is projected onto the surface of the rotating roller part 1 through the light projection fiber 31. The reflected light from the surface of the roller part 1 passes through a light receiving fiber 32 to a photodetector 35.
The light is projected onto the image plane, where it is photoelectrically converted. In this case, if there are defects such as unevenness on the surface of the roller part 1,
The scattered light intensity of the reflected light changes at the defective portion, and the level of the output signal from the photodetector 35 changes. This level change is examined in a processing section 36 equipped with various detection circuits, and thereby defects such as irregularities formed on the surface of the roller part 1 are detected. This detection operation is performed while the reflective optical fiber sensor 3 is slid parallel to the axial direction of the roller part 1.

Here, the output characteristics of the reflective optical fiber sensor 3 are:
It is determined by the luminous flux at the end face of the light receiving fiber 32. That is, in the model shown in FIGS. 5(a) and 5(b), the distance between the surface of the roller part 1 as the object to be inspected and the reflective optical fiber sensor 3 is Z, and the illuminance EO on the end surface of the light emitting fiber 31 is Then, the illumination intensity ΔE1 from the small area ΔS1 on the end face of the light emitting fiber 31 to the surface of the roller part 1 is ΔEl = EO
- Can be expressed as ΔS1/Z2. In addition, the end face of the light receiving fiber 32 has a small area ΔS on the end face of the light emitting fiber 31.
The illuminance ΔE received from the light-receiving fiber 32 is expressed as ΔE=E1 ·ΔS2 ·ρ, where ΔS2 is the minute area in the illuminance distribution extending over the end face of the light receiving fiber 32, and ρ is the reflectance of the roller part 1. Therefore, the luminous flux at the end face of the light receiving fiber 32 is determined by Φ=fΔE·ΔS. The output characteristics obtained based on this are shown by the solid line in FIG. 4. The broken line in FIG. 4 shows the output characteristic curve of a general reflective optical fiber sensor.

As described above, in the reflective optical fiber sensor 3 of this embodiment, the distance (gap m) between the roller part 1 and the head section 33 is the median value T of the distance range t corresponding to the saturation peak region of the output characteristics. Default setting.

Therefore, errors due to shape accuracy such as eccentricity can be eliminated, and detection operations can be performed with high accuracy. In other words, since the output characteristic value is saturated in the area between the range t in Fig. 4, the reflected light intensity does not change even if there is a change in distance, and the output changes due to eccentricity of the roller part 1, photographic error, etc. It will be cancelled. Therefore, according to the reflective optical fiber sensor 3 in this embodiment, only the defect signal of the roller part 1 can be detected satisfactorily.

In particular, in the device of this embodiment, as can be seen by comparing the solid line and the broken line in FIG. This is because the light emitting fiber 31 and the receiving fiber are arranged randomly as in the device of this embodiment, compared to the conventional system in which the light emitting fiber 31 and the receiving fiber are arranged randomly. optical fiber 3
This is because if the optical fibers are arranged in two divisions, even if the NA of the optical fibers is the same, the apparent upper diameter can be made different and the optical fibers can be made larger. In other words, in the conventional system in which the light emitting fiber and the light receiving fiber are randomly arranged, one light receiving fiber corresponds to one light emitting fiber, but as in the device of this embodiment, the light emitting fiber 31 and the light receiving fiber correspond to each other. In the case of a two-part arrangement with light receiving fiber 32, light emitting fiber 31 and light receiving)? The fibers 32 are formed into fiber bundles, so that the diameter of the upper fibers appears to be large, and the distance at which the output characteristic value is saturated and becomes the peak region becomes large. This means that the sensitivity of reflective fiber optic sensors has become less sensitive.

As shown in FIG. 6, in the waveform detected as the reflective optical fiber sensor 3 moves, the area corresponding to the area with large roughness on the surface of the defect is the area with a large roughness on the surface of the defect. It appears on the negative side of the detected waveform, and the area corresponding to the portion with small roughness on the surface of the defect appears on the positive side of the detected waveform from the defect-free surface. According to the experiment, it was possible to confirm the output of a convex defect with a height of 14 μm on a black matte cylindrical surface with a surface roughness RmaX of 3 μm. Comparing the example results shown in FIG. 6 with the detection results by the conventional device shown in FIG. 7, it can be seen that the S/N ratio has been significantly improved.

Although not shown, an encoder is attached to the motor 2 that rotates the roller part 1 as the object to be inspected, and a movement amount detection sensor is attached to the slide mechanism of the reflective optical fiber sensor 3. It is possible to detect in which part of the throat the defective part exists.

(Effects) As described above, the present invention allows the distance between the end face of the reflective optical fiber sensor and the surface of the object to be inspected to reach the peak region where the output characteristics of the reflective optical fiber sensor with respect to the distance are saturated. Therefore, even if there is a distance change due to eccentricity, the output of the reflective optical fiber sensor will not change, and the characteristic error caused by this can be canceled and the detection operation can be performed.
Defects on the surface of an object to be inspected can be detected accurately and at high speed with a simple structure without providing a complicated processing circuit.

[Brief explanation of the drawing]

1 and 2 are a side view and an external perspective view of a surface defect detection device according to an embodiment of the present invention, and FIG. 3 is a head portion of the device shown in FIGS. 1 and 2. FIG. 4 is a diagram showing the output characteristics of the reflective optical fiber sensor device shown in FIGS. 1 and 2, and FIGS. Fig. 6 is a line diagram showing the detection results by the device shown in Figs. FIG. 2 is a diagram showing output characteristics of a reflective optical fiber sensor device. DESCRIPTION OF SYMBOLS 1... Roller parts, 3... Reflective optical fiber sensor, 31... Light emitting fiber, 32... Light receiving fiber, 33... Head part, 34... Light emitting lamp, 35... Photo Detector. h4 Figure 30 Mouth ((1) (b)■'z and ?/note, fJru quantity warehouse 6 Figure collar recommendation (S) ÷7 sphere movement (S)

Claims (1)

[Claims] The tip of a reflective optical fiber sensor, which is integrally equipped with a light emitting fiber and a light receiving fiber, is placed close to the surface of the object to be inspected so as to face the surface of the object to be inspected. In a surface defect detection device that optically detects
A surface defect detection device characterized in that the output characteristic value of the reflective optical fiber sensor for the distance is set to a range corresponding to a peak region where the output characteristic value is saturated.