JP3256383B2 - Surface inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection apparatus for detecting a defect existing on the surface of an inspection object by scanning a spot light.

[0002]

2. Description of the Related Art Generally, a flying spot type surface inspection apparatus is used to detect a defect present on the surface of a continuously running sheet. This surface inspection device utilizes the difference in light reflectivity and transmittance between a normal part and a defective part, and scans the surface of an object to be inspected with a spot light by a laser, and reflects the reflected light or transmitted light. Photodetection is performed by a light receiver, and the presence or absence of various defects is evaluated based on the detection output. This surface inspection device detects the presence or absence of various defects such as surface color defects such as adhesion of foreign substances and the presence of irregularities, as well as abnormalities in surface color density and gloss, based on changes in the intensity of the detected reflected light and transmitted light. It can be inspected (for example, JP-A-59-220636).

There are various methods for receiving reflected light or transmitted light in this surface inspection apparatus, depending on the type of the object to be inspected and the type of defect to be detected. When a transparent object such as a plastic film is to be inspected and a defect that scatters light, such as a flaw on the surface or an air bubble inside, is to be detected, a transmission mask light receiving method is generally used. . In this transmission mask light receiving method, the light flux near the optical axis of the inspection light that has passed through the device under inspection is shielded, and only light scattered by a defect existing on the surface or inside of the device under inspection is incident on the light receiver. is there. According to this light receiving method, since a signal is output from the light receiver only when a defect exists, there is an advantage that the presence or absence of the defect can be immediately identified based on the presence or absence of the output signal.

The angle at which the inspection light is scattered varies depending on the type and degree of the defect. For example, a flaw defect existing on the surface of an object to be inspected scatters light at a relatively small angle, and a bubble defect existing inside is large. Scatters light at an angle. For this reason, it is necessary to detect all the light scattered at various angles in order to reliably detect the defect existing in the inspection object.

[0005]

In order to increase the light receiving angle of the light receiver, it is conceivable to widen the light receiving surface of the light receiver or to arrange the light receiver close to the object to be inspected. However, if the light-receiving surface is widened, the entire light-receiving device becomes large and the price becomes high, and the adjustment at the time of installing the light-receiving device becomes extremely difficult. On the other hand, in order to bring the light receiver closer to the object to be inspected, it is necessary to narrow the width of the mask for shielding the light flux near the optical axis. However, the linearity when scanning the inspection light and the ambient temperature Since the optical axis of the inspection light and the mask position have an error due to the thermal expansion of the light receiver due to the change of the mask, the mask width must be at least several times the spot diameter of the inspection light. For this reason, the distance between the object and the light receiving device is naturally limited, and the light receiving device cannot be brought closer to the object until the light receiving angle is sufficiently widened.

In order to solve the above problem, recently,
There is a surface inspection apparatus in which a plurality of light receivers are arranged so that light scattered within an angle range close to the optical axis of inspection light and light scattered at a large angle are separately detected. However, since this surface inspection apparatus uses a large number of expensive light receivers, not only does the price of the entire apparatus increase, but also the adjustment at the time of installation becomes difficult due to the increase in the number of members.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a low-cost surface inspection apparatus capable of simultaneously and reliably detecting defects having different light scattering properties. I do.

[0008]

In order to achieve the above object, a surface inspection apparatus according to any one of claims 1 to 3 is provided.
On the optical axis of the inspection light, and between the inspection part of the device to be inspected and the light receiver, a cylindrical lens extending in the scanning direction of the inspection light is provided, and the inspection light travels straight near the optical axis of the inspection light. An optical path adjusting lens is provided, which has a light transmitting portion for passing the light, and converges light incident outside the light transmitting portion toward the light receiver. It is preferable that the light passing portion of the optical path adjusting lens is formed in a hollow shape, or both the light incident surface and the light emitting surface are formed as flat surfaces.

Further, the surface inspection apparatus according to claim 4 is
The optical path adjusting lens is integrally connected to the front side of the light receiver.

Further, in the surface inspection apparatus according to the present invention, the width of the light passing portion of the optical path adjusting lens is W ₁ , the light receiving width of the light receiver is W ₂ , and the distance from the inspection section to the optical path adjusting lens is L.
_1, and the distance from the inspection unit to the light receiver and the L _2, is intended to satisfy the condition of _{W 1 = W 2 (L 1} / L 2).

[0011]

FIG. 1 schematically shows the basic structure of a surface inspection apparatus according to the present invention. The surface inspection device 10 includes a light emitter 11, a light receiver 12, an optical path adjusting lens 13, and an optical sensor 1.
4 and a signal processing circuit 15. A sheet-like film 17 to be inspected runs between the light projector 11 and the light receiver 12 at a constant speed in the direction of the arrow in the figure.

The projector 11 comprises a laser oscillator 20, a lens group 21, a rotating polygon mirror 22, and two mirrors 23 and 24 for bending the optical path. The laser beam 20a emitted from the laser oscillator 20 is
The light enters the lens group 21 via the lens 3, and after its spot diameter is adjusted, enters the rotating polygon mirror 22 rotating at a high speed via the mirror 24. And this laser beam 20a
Is inspection light 25 that scans the film 17 in the width direction at a high speed substantially orthogonal to the running direction of the film 17 by the rotation of the rotating polygon mirror 22. This inspection light 25 is applied to the film 17.
The light is emitted from the light projecting unit 11 toward the inspection unit 17a, passes through the inspection unit 17a, and then enters the light receiver 12 extending in the scanning direction via the optical path adjusting lens 13.

As shown in FIG.
5, a mask 26 is provided at the center of the light receiving lens 12a for blocking the light flux of the inspection light 25 near the optical axis 25a. This light receiver 1
2 photoelectrically detects the inspection light 25 transmitted through the inspection unit 17a of the film 17 and incident on the light receiving lens 12a, and sends out a photoelectric conversion signal proportional to the intensity to the signal processing circuit 15.

The optical path adjusting lens 13 is composed of a cylindrical lens extending in the scanning direction.
a, and between the inspection unit 17a and the light receiver 12. At the center of the optical path adjusting lens 13, a hollow light passing portion 13a is formed. The width W ₁ of the light passing portion 13 a is L ₁ , the distance from the inspection portion 17 a to the optical path adjusting lens 13, the distance L ₂ from the inspection portion 17 a to the light receiver 12, and the width of the light receiving window 12 b of the light receiver 12. When W ₂ is set, it is set so as to satisfy the relational expression W ₁ = W ₂ (L ₁ / L ₂ ). Therefore, the light passing portion 13
a has a size to pass straight through the light scattered within the acceptance angle theta ₂ of the light receiver 12 of the inspection light 25 transmitted through the inspection section 17a. Also, the optical path adjusting lens 13
The lens surface 13b is formed such that the entire incident surface on the film 17 side is convex and the exit surface on the light receiver 12 side is flat, and the incident light is substantially parallel to the optical axis 25a of the inspection light 25. The light is refracted in the direction and converges toward the light receiving lens 12a of the light receiver 12.

Here, as shown in FIG. 3, the closer the optical path adjusting lens 13 is to the inspection unit 17a, that is, the distance L
About ₁ becomes shorter, the acceptance angle θ ₁ increases. Since it is preferable that the light receiving angle θ ₁ of the optical path adjusting lens 13 is as large as possible, the optical path adjusting lens 13 is arranged close to the inspection unit 17a, and the distance L ₁ at this time and the inspection unit 17 the ratio of the distance L ₂ to, and based on the value of the width W ₂ of the light receiving window 12b, may be determined width W ₁ of the light passing portion 13a. In this embodiment, the light receiver 12
Width W of the distance L ₂ and the light receiving window 12b from the test portion 17a of the
₂ is 600mm each as with the conventional surface inspection device
And the inspection unit 17a of the optical path adjusting lens 13
Width W ₁ of the distance L ₁ 100 mm, the light passing portion 13a from
Was set to 5 mm. In addition, the entire width of the light path adjusting lens 13 in substantially the same width as the width W ₂ of the light receiving window 12b. Thus, the light receiving angle θ ₁ of the optical path adjusting lens 13 is
Is “6 times” the light receiving angle θ ₂ of

The optical sensor 14 is provided at a position deviated from the scanning area X on the film 17 by the inspection light 25 to the scanning upstream side, and generates a pulse-like light receiving signal at the moment when the inspection light 25 is received. The signal is sent to the signal processing circuit 15.

FIG. 4 schematically shows the structure of the signal processing circuit 15. The signal processing circuit 15 includes an inspection width setting circuit 31, a filter circuit 32, a binarization circuit 33, and an AND circuit 34. The light receiving signal S1 of the optical sensor 14 is input to the inspection width setting circuit 31. The inspection width setting circuit 31 converts the inspection width signal S2 from a low level to a high level when the time _Ta has elapsed since the input of the light receiving signal S1 and returns to a low level again after the time _Tb has elapsed, and an AND circuit 34. Output to Note that time T
_a, T _b is preset in accordance with the width dimension of the scanning speed and the film 17, until the time T _a reach inspection start position on the inspection portion 17a from the inspection light 25 passes through the optical sensor 14 time, time T _b is set to a time from when passing through the optical sensor 14 to reach the inspection end position on the test section 17a.

The photoelectric conversion signal S3 from the light receiver 12 is input to a filter circuit 32. Filter circuit 32
Removes the low-frequency and high-frequency noise components contained in the photoelectric conversion signal S3 and sends the output signal S4 to the binarization circuit 33. The binarization circuit 33 includes the filter circuit 3
When the signal level of the output signal S4 from the second unit 2 exceeds a preset threshold value L _THLD , a light quantity increase signal S5 which becomes a high level is generated and sent to the AND circuit 34. The AND circuit 34 performs the binarization circuit 3 while the inspection width signal S2 from the inspection width setting circuit 31 is at the high level.
When the light amount increase signal S5 is input from No. 3, a defect signal S6 is transmitted at this timing.

Next, the operation of the present embodiment will be described with reference to FIG. 5 showing a schematic waveform of each output signal of the surface inspection apparatus 10. The film 17 runs at a constant speed, and at the same time, the irradiation of the inspection light 25 from the light projector 11 is started. Inspection light 2
When 5 passes through the optical sensor 14, the sensor 14 generates a pulsed light receiving signal S 1 and sends it to the inspection width setting circuit 31. The inspection width setting circuit 31 outputs the inspection light 25 to the film 17 after _a lapse of time Ta since the light receiving signal S1 is input.
, The signal level is changed from low level to high level. When the time _Tb has elapsed and the inspection light 25 has reached the inspection end position of the film 17, the inspection width setting circuit 31 returns the signal level to the low level again. Therefore, the inspection width signal S2 output from the inspection width setting circuit 31 is such that the inspection light 25 is
7 is at a high level only during scanning on the inspection section 17a.

The inspection light 25 transmitted through the inspection unit 17 a of the film 17 enters the light receiver 12 via the optical path adjusting lens 13. The light receiver 12 photoelectrically detects the inspection light 25 and outputs a photoelectric conversion signal S3 proportional to the intensity of the inspection light 25. At this time, when no defect exists on the inspection unit 17a, the inspection unit 17a
Of the inspection light 25 that has passed through the optical path adjusting lens 13 passes through the light passing portion 13a formed in the center of the optical path adjusting lens 13 and directly enters the mask 26. Therefore, the photoelectric conversion signal S3 of the light receiver 12 has a low level. Will remain. However, film 1
At the end of 7, light is generally scattered, so
This scattered light enters the light receiving window 12b, and the photoelectric conversion signal S
3, the signal level increases.

On the other hand, when a defect exists on the inspection unit 17a, the inspection light 25 is scattered and transmitted from the inspection unit 17a at various angles. The light scattered within the range of the light receiving angle θ ₂ of the light receiver 12 is transmitted to the light passage portion 13 a of the optical path adjusting lens 13.
, And enters the light receiving lens 12a of the light receiver 12.
At this time, since the light passage portion 13a is formed hollow,
The light incident on the light passing portion 13a passes straight toward the light receiving lens 12a, and the light scattered at a small angle near the optical axis 25a is refracted in the direction of the optical axis 25a again and does not enter the mask 26. .

The light scattered out of the range of the light receiving angle θ ₂ of the light receiver 12 is incident on the lens surface 13b of the optical path adjusting lens 13, and its light path is refracted and converged on the light receiving lens 12a. At this time, the light receiving angle θ ₁ of the optical path adjusting lens 13 is
Since the angle is set to approximately six times the light receiving angle θ ₂ of the light receiver 12, most of the light scattered by the inspection unit 17a can be made incident on the lens surface 13b and converged on the light receiving lens 12a. Thus, the photoelectric conversion signal S3 of the light receiver 12, a position corresponding to the defect, reliably signal level is abnormal signal S _E is generated increases.

The photoelectric conversion signal S3 of the light receiver 12 is sent to a binarization circuit 33 after low-frequency and high-frequency noise components are removed by a filter circuit 32. Binarization circuit 33
When the signal level of the output signal S4 from the filter circuit 32 becomes _{equal to} or greater than a preset threshold value L _THLD , a light amount increase signal S5 is generated and sent to the AND circuit 34. At this time, the output signal S from the filter circuit 32
4 rises at the position where the abnormal signal _SE is generated and at the end of the film 17, the binarization circuit 33 increases the light amount at the position where the abnormal signal _SE is generated and at the end of the film. A signal S5 is generated. The AND circuit 34 performs the binarization circuit 3 while the inspection width signal S2 is at the high level.
3, when the light amount increase signal S5 is input, the defect signal S6
Is sent. Accordingly, the abnormality signal only defect signal S6 at the position corresponding to the S _E is generated. Then, the defect signal S
When 6 is sent to a CPU (not shown), the CPU displays "defective" on, for example, a display panel (not shown).

In the above embodiment, an example was described in which the light-passing portion of the optical-path adjusting lens was hollow, but the light-passing portion only has to pass incident light straight. Like the adjusting lens 40, both the entrance surface 41a and the exit surface 41b of the light passing portion 41 may be formed to be flat surfaces. According to this embodiment, it is possible to easily manufacture the existing cylindrical lens by flattening the central part of the convex surface of the cylindrical lens.

In the above embodiment, the optical path adjusting lens and the light receiver are separately provided. However, as shown in FIG.
May be integrated so as to be coaxial. According to this embodiment, since the number of members is reduced, the handling is simplified, and at the time of installation, only the distance between the film 48 and the optical path adjusting lens 46 needs to be adjusted.

In the above embodiment, an example was described in which the present invention was applied to a transmission type surface inspection apparatus for photoelectrically detecting light transmitted through an inspection section. However, the present invention detects light reflected by the inspection section. Of course, the present invention can also be applied to a reflection type surface inspection apparatus.

[0027]

As described above, according to the surface inspection apparatus of the present invention, an optical path adjusting lens for converging incident light toward the light receiver is provided between the inspection unit and the light receiver. The light receiving angle is greatly expanded, and it becomes possible to cope with the detection of defects having various scattering angles. Moreover, since only one light receiver is provided, an increase in the number of members can be suppressed, and the cost of the entire apparatus can be reduced. In addition, a light passing portion is formed at the center of the optical path adjusting lens to allow light to travel straight and pass therethrough, and light scattered within the light receiving range of the light receiving device is directly incident on the light receiving device. The light scattered at a very small angle is refracted again in the optical axis direction, thereby preventing a defect from being detected. In addition, simply arranging the optical path adjusting lens between the inspection unit and the light receiver allows the light scattered over a wide angle range to converge on the light receiver. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a surface inspection apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between an optical path adjusting lens, a light receiver, and inspection light.

FIG. 3 is an explanatory diagram showing a relationship between a distance from an inspection unit of the optical path adjusting lens and a light receiving angle.

FIG. 4 is a block diagram illustrating a configuration of a signal processing circuit.

5 is a chart showing an outline of a signal waveform in each section of the signal processing circuit shown in FIG. 4;

FIG. 6 is a schematic diagram showing another configuration example of the optical path adjusting lens.

FIG. 7 is a schematic diagram showing another example of the arrangement of the optical path adjusting lens.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 surface inspection device 11 light emitter 12, 47 light receiver 13, 40, 46 optical path adjusting lens 13 a, 41 light passing unit 15 signal processing circuit 17 film 17 a inspection unit 25 inspection light 25 a optical axis 26 mask

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/84-21/958

Claims (5)

(57) [Claims] An inspection light is applied to a continuously running transparent inspection object, and the inspection light is scanned in a direction crossing the traveling direction of the inspection object. The detector is arranged along the scanning direction of, and the incidence of inspection light that has transmitted specularly through the device under inspection is blocked. By photoelectrically detecting the scattered transmitted light from the inspection section of the device under inspection, the presence or absence of a defect is identified. A surface inspection apparatus, comprising: a cylindrical lens extending in the scanning direction of the inspection light on the optical axis of the inspection light and between the inspection unit and the light receiver; A surface inspection apparatus, wherein a light passage portion is formed for allowing the light to pass straight through and a light path adjusting lens for converging light incident outside the light passage portion toward the light receiver is provided. 2. The surface inspection apparatus according to claim 1, wherein the light passage portion of the optical path adjusting lens is formed in a hollow. 3. The surface inspection apparatus according to claim 1, wherein the light passing portion of the optical path adjusting lens has flat surfaces on both the entrance surface and the exit surface. 4. The surface inspection apparatus according to claim 2, wherein the optical path adjusting lens is integrally connected to a front side of the light receiver. 5. The width of a light passing portion of the optical path adjusting lens is W
₁ , when the light receiving width of the light receiver is W ₂ , the distance from the inspection unit to the optical path adjusting lens is L ₁ , and the distance from the inspection unit to the light receiver is L ₂ , W ₁ = W ₂ (L ₁ / L ₂ ) The surface inspection apparatus according to claim 2, wherein the following condition is satisfied.