JPH0719838A - Method and apparatus for visual inspection - Google Patents

Abstract

PURPOSE:To detect gentle irregularities, where shadows are not formed. CONSTITUTION:When an outer surface 38 of a work 10 is flat, the relative positions of an optical sensor 42 and a light source 40 are set so that the regular reflected light component is not incident on the optical sensor 42. When the electric signal SS of the optical sensor 42 is larger than a predetermined judgment value, it is judged that irregularities are present on the outer surface 38. When the optical sensor 42 and the light source 40 come into the symmetrical positions with the normal line of the surface of the irregularities in-between when the gentle irregularities are preset on the outer surface 38, the regular reflected light component is incident on the optical sensor 42, and the strength of the electric signal SS becomes stronger. Therefore, the presence or absence of the irregularities can be judged based on whether the electric signal SS is larger than the judgment value or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection method and apparatus for irradiating a work surface with light to detect reflected light and determining the presence or absence of irregularities on the work surface based on the intensity of the reflected light. is there.

[0002]

[Prior art]

(A) A light source that irradiates the work surface with light, and (b) receives the reflected light that is arranged at a predetermined position with respect to the light source and reflected by the work surface, and outputs an electrical signal corresponding to the light intensity. An appearance inspection method that includes an output optical sensor and detects the unevenness of the work surface based on the strength of the electric signal is used, for example, for the surface inspection of a stator core that has been electrodeposition coated. FIG. 11A is a diagram for explaining the principle of such a visual inspection method, and shows the surface 1 of the work 110.
The light sensor 114 is disposed substantially perpendicular to the light source 12, and the light source 116 irradiates the surface 112 with light obliquely.
Although an electric signal of a predetermined intensity is output from the optical sensor 114 due to the scattered light reflected by the optical sensor 1, when the surface 112 has irregularities such as a flaw or a protrusion, a shadow is formed, so that the optical sensor 1
The electrical signal 14 is reduced in the shaded area as shown in (b), and the presence or absence of the unevenness is determined based on the reduced intensity of the electrical signal. The optical sensor 114 is a line sensor having a large number of photoelectric conversion elements in the width direction of the work 110, that is, in the direction perpendicular to the paper surface, and (b) shows the electric signals of the photoelectric conversion elements arranged in the order of acquisition. It corresponds to the width of the work 110. Therefore, the entire area of the surface 112 can be inspected by moving the work 110 in the left-right direction in FIG.

[0003]

However, with such a conventional appearance inspection method, it is not possible to detect unevenness that changes gently as shown in FIGS. 6 (a) and 7, for example. That is, although it varies depending on the irradiation angle of light from the light source, a shadow cannot be formed in the case of gentle unevenness, so the electric signal of the optical sensor hardly decreases, and the presence or absence of unevenness is determined based on the decrease in the intensity of the electric signal. You cannot do it. For example, in the case of a stator core of a motor, if a slight bulge does not enter the case, it is desired to be able to detect even such a gentle unevenness.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable detection of gentle unevenness such that a shadow cannot be formed.

[0005]

In order to achieve such an object, the first invention is (a) a light source for irradiating a work surface with light, and (b) a predetermined light source. An optical sensor that is disposed at a position and receives the reflected light reflected by the work surface, and that outputs an electric signal corresponding to the light intensity, and detects the unevenness of the work surface based on the strength of the electric signal. In the inspection method, (c) the optical sensor is arranged at a position where a specular reflection light component does not enter when the work surface is flat, and an electric signal output from the optical sensor is larger than a predetermined judgment value. In this case, it is characterized in that it is determined that the work surface has irregularities.

[0006]

[Advantageous Effects and Advantages of the First Invention] That is, the positional relationship between the optical sensor and the light source is such that the regular reflection light component reflected by the workpiece surface does not enter the optical sensor if the workpiece surface is flat as in the conventional case. The optical sensor outputs an electric signal of a predetermined intensity due to scattered light, but when the electric signal is larger than a predetermined judgment value, in other words, when the intensity of the light received by the optical sensor is strong, The difference is that it is determined that there are irregularities on the surface. To be more specific, when there is gentle unevenness on the surface of the work, the path of the reflected light changes due to the unevenness, and the optical sensor and the light source are located symmetrically with respect to the normal line of the surface of the uneven part. As shown in FIGS. 6 and 7, since the specular reflection light component is incident on the optical sensor and the electric signal becomes large, it is possible to determine the presence or absence of unevenness from the increase in the intensity of the electric signal. As a result, it becomes possible to favorably detect a gentle unevenness such that a shadow cannot be formed.

Even when the electric signal is smaller than another judgment value lower than the signal strength when the surface of the work is flat,
If it is determined that there is unevenness on the surface of the work, it is possible to detect a sharp flaw, a protrusion, or the like that produces a shadow as in the conventional case.

[0008]

[Second Means for Solving the Problems] The second invention is
(A) A light source that irradiates the work surface with light, and (b) receives the reflected light that is arranged at a predetermined position with respect to the light source and reflected by the work surface, and outputs an electrical signal corresponding to the light intensity. In the appearance inspection method, comprising: an optical sensor for outputting, and detecting irregularities on the surface of the work based on the intensity of the electric signal, (c) the optical sensor is a specular reflection light component when the surface of the work is flat. Is arranged at a position where the light enters, and when the electric signal output from the optical sensor is smaller than a predetermined judgment value, it is judged that the work surface has unevenness.

[0009]

According to the second aspect of the present invention, the positional relationship between the optical sensor and the light source is determined so that the specularly reflected light component reflected by the work surface is incident on the optical sensor if the work surface is flat. If the electrical signal output from the optical sensor is smaller than a predetermined determination value, it is determined that the unevenness exists. That is, not only when there are steep flaws or protrusions on the surface of the work and shadows are formed, but also when there is gentle unevenness, the path of the reflected light changes and the specularly reflected light component does not enter the optical sensor. And the electrical signal output from the optical sensor is lower than when the work surface is flat,
The presence or absence of irregularities can be determined from the decrease in the intensity of the electric signal. According to the second aspect of the invention, not only the gentle unevenness but also the steep unevenness can be favorably detected.

[0010]

[Third Means for Solving the Problems]
(A) A light source that irradiates the work surface with light, and (b) receives the reflected light that is arranged at a predetermined position with respect to the light source and reflected by the work surface, and outputs an electrical signal corresponding to the light intensity. An optical inspection device for outputting irregularities on the surface of the work based on the intensity of the electric signal, wherein (c) the optical sensor is a specular reflection light when the work surface is flat. The component is arranged at a position where no component is incident, and (d) it has a comparison means for determining that the work surface has irregularities when the electric signal output from the optical sensor is larger than a predetermined determination value. It is characterized by

[0011]

That is, the third aspect of the present invention relates to an appearance inspecting apparatus for performing an appearance inspection according to the first aspect of the invention, and in a position where a specular reflection light component does not enter when the work surface is flat. The optical sensor is arranged, and the electric signal output from the optical sensor is compared with a predetermined judgment value by the comparison means to judge that the unevenness exists when the electric signal is larger than the judgment value. Similar to the first aspect, it is possible to satisfactorily detect gentle unevenness.

[0012]

[Fourth Means for Solving the Problems]
(A) A light source that irradiates the work surface with light, and (b) receives the reflected light that is arranged at a predetermined position with respect to the light source and reflected by the work surface, and outputs an electric signal corresponding to the light intensity. An optical inspection device for outputting an irregularity of the surface of the work based on the strength of the electric signal, (c) the optical sensor is a specular reflection light component when the work surface is flat. Is disposed at a position where the incident light is incident, and (d) it has a comparison means for determining that the work surface has irregularities when the electric signal output from the optical sensor is smaller than a predetermined determination value. Is characterized by.

[0013]

That is, the fourth aspect of the present invention relates to an appearance inspecting apparatus for performing an appearance inspection according to the second aspect of the present invention. When a work surface is flat, a specular reflection light component is incident on a light incident position. The sensor is arranged, and the electric signal output from the optical sensor is compared with a predetermined judgment value by the comparison means, and when the electric signal is smaller than the judgment value, it is judged that the unevenness exists. Similar to the invention, it is possible to satisfactorily detect gentle unevenness or steep unevenness.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an apparatus for visually inspecting a work 10 such as a ring-shaped stator core that has been electrodeposited, and is equipped with six stations ST1 to ST6.
0 is fed to the first station ST1 and is intermittently fed counterclockwise as the rotary plate 12 rotates. The rotary plate 12 is rotatably supported by a support shaft 14 via a bearing (not shown), and the motor 16
Thus, the belt is intermittently rotated at intervals of 60 ° via the timing belt 18. Six holding frames 20 are provided at 60 ° intervals on the outer peripheral portion of the rotary plate 12, while a plurality of guide plates 22 are fixedly disposed on the outer peripheral side of the rotary plate 12, so as to fix the workpiece 10. Are held and sent between the holding frame 20 and the guide plate 22.

The second station ST2 is a place for inspecting the outer peripheral surface of the work 10, and the third station ST3 is a place for inspecting the end surface of the work 10. Each pair of drive rollers 24, 26 and its drive roller 24. ，
Motors 28 and 30 for rotating 26 are provided. In the inner peripheral side portion of the holding frame 20 of the rotating plate 12,
A pressing member 32, which is biased toward the outer peripheral side by a spring (not shown), is provided.
Thus, the work 10 is pressed by the drive rollers 24 and 26, and is rotated about the axis along with the rotation of the drive rollers 24 and 26. In addition, in the fourth station ST4, the inspection results of the stations ST2 and ST3 are OK.
In the place where the work 10 was discharged, the fifth station ST5 was the work 10 in which any inspection result was NG.
The fourth station ST4 is provided with a shutter 34 that closes the discharging portion. The shutter 34 is opened and closed by an actuator 36, and the actuator 36 is driven by a controller (not shown) according to the inspection results of the stations ST2 and ST3.

As shown in FIG. 2, the second station ST2 receives a light source 40 for irradiating the surface of the work 10, that is, the outer peripheral surface 38, and reflected light reflected by the outer peripheral surface 38. Electric signal S corresponding to the light intensity
An optical sensor 42 that outputs S is provided. The optical sensor 42 is arranged so that its optical axis is substantially orthogonal to the axial center of the workpiece 10, in other words, substantially perpendicular to the outer peripheral surface 38, while the light source 40 is provided with the optical sensor 42. From the direction inclined by the angle α with respect to the optical axis, the outer peripheral surface 38
It is arranged so as to irradiate light. Therefore, if the outer peripheral surface 38 is flat and, strictly speaking, is a smooth arc surface centered on the axis, the specularly reflected light component does not enter the optical sensor 42, and only the scattered light component enters. But,
If the angle α is too large, the sensor output becomes substantially zero as shown in FIG. 3, and shadows caused by steep flaws or protrusions cannot be detected. Therefore, it is desirable to set the angle α in the range of about 30 ° or less. . The optical sensor 42 is used for the work 10.
Of the line sensor having a large number of photoelectric conversion elements in the width direction of the work sheet, that is, in the direction perpendicular to the paper surface, the light intensity of the reflected light in the width direction of the work 10 is detected by one scan (signal acquisition from each photoelectric conversion element). , The work 10 is the motor 2
8. By being rotated once by the drive roller 24, the light intensity of the entire outer peripheral surface 38 of the work 10 can be detected.

The optical sensor 42 is connected to the flaw determination circuit shown in FIG. 4, and the electric signal SS output from the optical sensor 42 is supplied to the first comparator 44 and the second comparator 46. The first comparator 44 compares the voltage value of the electric signal SS with the first judgment value V1 set by the setter 48, and when the electric signal SS is larger than the first judgment value V1, the defect signal SK.
1 is output. The first determination value V1 is higher than the voltage value of the electric signal SS when the outer peripheral surface 38 is flat, and the outer peripheral surface 38 has gentle irregularities as shown in FIGS. The value is lower than the voltage value of the electric signal SS when it is incident on the beam 42, and is set in advance by experiments or the like based on the surface material of the work 10, the angle α, and the like. Further, the second comparator 46 compares the voltage value of the electric signal SS with the second judgment value V2 set by the setter 50, and outputs the flaw signal SK2 when the electric signal SS is smaller than the second judgment value V2. To do. The second determination value V2 is the electric signal SS when the outer peripheral surface 38 is flat.
11 is lower than the voltage value of the electric signal SS and is higher than the voltage value of the electric signal SS in the case where a shadow is formed by sharp irregularities such as scratches and protrusions as shown in FIG. .

The flaw signal SK1 output from the first comparator 44 and the flaw signal S output from the second comparator 46.
K2 is supplied to the OR circuit 52, and a defect signal SK obtained by combining both defect signals SK1 and SK2 is supplied to the counter 54. A work signal SW indicating whether or not the work 10 exists in the second station ST2 is supplied to the counter 54 from a work detection sensor (not shown) provided in the second station ST2. The number of flaw signals SK supplied during the inspection of each work 10 is counted, and the number is output to a controller (not shown) such as a personal computer. The controller determines NG when the number of flaw signals SK supplied from the counter 54 is, for example, a preset value or more, and drives the actuator 36 so that the work 10 is not ejected from the fourth station ST4. To do so. FIG. 5 shows the optical sensor 4 in one scan.
2 is a diagram showing the relationship between the electric signal SS captured from each photoelectric conversion element of No. 2 and the defect signals SK1, SK2, and SK, where W is the width of the work 10 and among the electric signals SS output from the optical sensor 42. , The part W relating to the work 10 is supplied to the comparators 44 and 46.

In such a visual inspection apparatus, if the outer peripheral surface 38 is flat, the light source 40 and the optical sensor 42 are arranged so that the specularly reflected light component reflected by the outer peripheral surface 38 does not enter the optical sensor 42. , The electric signal SS output from the optical sensor 42 is compared with a preset first determination value V1 higher than the voltage value of the electric signal SS when the outer peripheral surface 38 is flat, and the electric signal SS is Since the flaw signal SK1 is output from the first comparator 44 when it is larger than the first judgment value V1, even if the outer peripheral surface 38 has a gentle unevenness, it can be detected well. That is, when there is a gentle bulge on the outer peripheral surface 38 as shown in FIG. 6A, the path of the reflected light changes due to the bulge, and the optical sensor 42 and the light source 40 are sandwiched by the normal to the surface of the bulge. When and are at symmetrical positions, the specular reflection light component is incident on the optical sensor 42 and the electric signal SS becomes large as shown in FIG. 6B, so that the defect signal SK1 is output from the first comparator 44. Is done. Even when the outer peripheral surface 38 has a gentle depression, the specular reflection light component enters the optical sensor 42 as shown in FIG. 7, so that the signal intensity of the electric signal SS increases and the first comparator 44 increases. Defect signal SK1 is output from. This embodiment is one embodiment of the first invention and the third invention, and the first comparator 44 corresponds to the comparing means of the third invention.

On the other hand, in the present embodiment, the electric signal S is compared with the preset second judgment value V2 lower than the voltage value of the electric signal SS when the outer peripheral surface 38 is flat.
Since the second comparator 46 that outputs the flaw signal SK2 when S is smaller than the second determination value V2 is provided, there are sharp flaws and projections as shown in FIG. Even when it is possible, the unevenness can be detected well.

Next, one embodiment of the second invention and the fourth invention will be described. In the following embodiments, parts that are substantially common to the first embodiment are given the same reference numerals and detailed description thereof is omitted.

In FIG. 8, the positional relationship between the optical sensor 42 and the light source 40 is such that when the outer peripheral surface 38 is flat, the outer peripheral surface 3 is flat.
It is set so that the specularly reflected light component of the light reflected at 8 is incident on the optical sensor 42, in other words, the optical sensor 42 and the light source 40 are symmetric with respect to the normal line of the outer peripheral surface 38. . Then, the electric signal SS output from the optical sensor 42 is supplied to the comparator 60 of the defect judgment circuit shown in FIG. 9, and the voltage value of the electric signal SS is compared with the judgment value V3 set by the setter 62, When the electric signal SS is smaller than the determination value V3, the flaw signal SK is output. The determination value V3 in this case is lower than the voltage value of the electric signal SS when the outer peripheral surface 38 is flat and the specular reflection light component is incident on the optical sensor 42, and is gentle as shown in FIG. The value is higher than the voltage value of the electric signal SS when the specular reflection light component does not enter the optical sensor 42 due to the unevenness, and is set in advance by experiments or the like.

In this embodiment, when the outer peripheral surface 38 has a gentle bulge as shown in FIG. 10A, the specular reflection light component does not enter the optical sensor 42 in the bulge range E, so that the electric The signal SS drops as shown in FIG. 10B, and the defect signal SK is output from the comparator 60. Also,
When there is a gentle depression as shown in FIG.
Even when a sharp flaw or protrusion is present and a shadow is formed as shown in (a) of 1, the signal strength of the electric signal SS is reduced and the flaw signal SK is output. As described above, in the present embodiment, only one comparator 60 can detect both gentle unevenness and steep unevenness. In this embodiment, the comparator 60 corresponds to the comparing means of the fourth invention. Note that it is desirable to use the output of the optical sensor 42 near the saturation level in order to increase the resolution.
Further, by setting the judgment value V3 as the second judgment value V2, the flaw judgment circuit of FIG. 4 can be used as it is.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above-described embodiment, the case where the outer peripheral surface 38 of the cylindrical work 10 is inspected has been described. However, as long as it has a basically flat surface shape, it can be used for appearance inspection of various works. The invention can be applied.

Further, in the first embodiment, the optical sensor 42 is arranged in a posture substantially vertical to the outer peripheral surface 38, but the specular reflection light component of the light emitted from the light source 40 to the outer peripheral surface 38. The position where the optical sensor 42 and the light source 40 are disposed can be changed as appropriate as long as the light is not incident.

In the above embodiment, the comparators 44, 46,
Although the presence / absence of irregularities is determined by 60, the presence / absence of irregularities may be determined by comparing the electric signal SS with the determination values V1, V2, V3 by signal processing by a microcomputer or the like.

Further, in the above-mentioned embodiment, whether the work 10 is good or bad is judged by the presence or absence of unevenness, or more accurately, the number of flaw signals SK. However, the size and position of the unevenness can be obtained based on the electric signal SS. You can also

Further, in the above-described embodiment, the work 10 is rotated for the inspection, but it is also possible to perform the appearance inspection while moving the light source 40 and the optical sensor 42 relative to the work 10.

Although not illustrated one by one, the present invention can be carried out in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a plan view of an appearance inspection apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional relationship between a light source and an optical sensor, which are arranged to inspect an outer peripheral surface of a work in the appearance inspection apparatus of FIG.

3 is a diagram showing a relationship between an angle α of FIG. 2 and an output of an optical sensor.

4 is a circuit diagram of a flaw determination circuit to which an electric signal SS output from the optical sensor of FIG. 2 is supplied.

5 is a diagram showing a relationship between signals SS, SK1, SK2, and SK in FIG.

FIG. 6 is a diagram for explaining that the specular reflection light component is incident on the optical sensor of FIG. 2 when the bulge is present on the outer peripheral surface of the work, and the signal intensity increases.

FIG. 7 is a diagram showing a state in which a specularly reflected light component is incident on the optical sensor of FIG. 2 when a gentle depression is present on the outer peripheral surface of the work.

FIG. 8 is a diagram showing a case where a light source and an optical sensor are arranged such that a specularly reflected light component is incident on the optical sensor when the surface is flat.

9 is a circuit diagram of a flaw determination circuit to which an electric signal SS output from the optical sensor of FIG. 8 is supplied.

FIG. 10: When the outer peripheral surface of the work has a gentle bulge, the specular reflection light component does not enter the optical sensor of FIG.
It is a figure explaining that signal strength falls.

FIG. 11 is a diagram illustrating a conventional appearance inspection method in which a signal intensity of an optical sensor is reduced due to a shadow formed by a flaw or a protrusion, and unevenness is detected based on the intensity reduction.

[Explanation of symbols]

 10: Work piece 38: Outer peripheral surface (front surface) 40: Light source 42: Optical sensor 44: First comparator (comparing means of the third invention) 60: Comparator (comparing means of the fourth invention) SS: Electric signal

Claims (4)

[Claims] 1. A light source for irradiating a work surface with light, and light reflected by the work surface, which is arranged at a predetermined position with respect to the light source, receives the reflected light, and outputs an electric signal corresponding to the light intensity. In the appearance inspection method for detecting unevenness of the work surface based on the strength of the electric signal, a specular reflection light component does not enter when the work surface is flat. A visual inspection method, characterized in that it is arranged at a position, and when the electric signal output from the optical sensor is larger than a predetermined judgment value, it is judged that unevenness exists on the surface of the work. 2. A light source for irradiating the work surface with light, and a reflected light which is arranged at a predetermined position with respect to the light source and reflected by the work surface, and outputs an electric signal corresponding to the light intensity. In the appearance inspection method for detecting irregularities of the work surface based on the strength of the electric signal, the optical sensor is a position where a specular reflection light component is incident when the work surface is flat. The appearance inspection method is characterized in that, when the electric signal output from the optical sensor is smaller than a predetermined judgment value, it is judged that the work surface has irregularities. 3. A light source for irradiating a work surface with light, and light reflected by the work surface which is arranged at a predetermined position with respect to the light source and receives an electric signal corresponding to the light intensity. In the visual inspection apparatus, which includes an optical sensor for detecting the unevenness of the work surface based on the strength of the electric signal, the optical sensor does not enter a specular reflection light component when the work surface is flat. The appearance inspection, which is arranged at a position and has a comparison means for determining that there is unevenness on the work surface when the electrical signal output from the optical sensor is larger than a predetermined determination value. apparatus. 4. A light source for irradiating the work surface with light, and a reflected light which is arranged at a predetermined position with respect to the light source and reflected by the work surface, and outputs an electric signal corresponding to the light intensity. In the visual inspection apparatus, which comprises an optical sensor for detecting the unevenness of the work surface based on the strength of the electric signal, the optical sensor is a position where a specular reflection light component is incident when the work surface is flat. Is located in
An appearance inspection apparatus comprising: a comparison unit that determines that unevenness exists on the surface of the work when an electric signal output from the optical sensor is smaller than a predetermined determination value.