JP2007285935A - Lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system enabling with one system, quick detection of a different kind of defect over the whole surface of a sheet-like object by visual inspection. <P>SOLUTION: This lighting system 10 is constituted of three light guides 1 for illuminating an inspection object such as a film or a sheet; an inspection plate 2 arranged over the light guides 1, loaded with the inspection object, and having a function for diffusing light emitted from the light guides 1; and a stage 3 for fixing the three light guides 1. The stage 3 is moved up and down movably in the vertical direction by a lifting mechanism 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an illumination device for detecting defects in a transparent sheet-like inspection object such as a film or a sheet.

  Conventionally, an illuminating device has been used for detecting a defect in a transparent sheet such as a film or a sheet. In general, the types of defects found in sheet-like materials include foreign matter defects, stain defects, fish eye defects, uneven defects, etc., and for foreign matter defects and stain defects in sheet-like materials, light is applied to the inspection object. Although the presence or absence of a defect can be determined by the brightness of the transmitted light when incident, the fish eye defect or irregularity defect in the sheet can be confirmed when the light source of the lighting device is directly under the defect. Have difficulty. However, it is generally known that these defects can be detected at a light / dark boundary (edge portion) formed by light emitted from a light source. Therefore, a surface illumination device that can quickly inspect the entire surface without moving the inspection object is used to detect foreign matter and dirt defects, while a fish-eye defect and uneven defect are detected from a light source. In general, a line-shaped illumination device having a narrow width is used because the edge portion of the emitted light is used.

Here, in a typical planar illumination device using a fluorescent lamp as a light source, as shown in FIG. 5, one fluorescent lamp 102 is provided on each of the left and right sides of the light guide plate 101 that guides the light while scattering the light. Surface illumination is realized by arranging them one by one and making light enter the light guide plate.
On the other hand, as an illumination method using an edge portion of illumination light, a line-shaped illumination device is used, and a light-shielding portion is arranged between the line-shaped illumination device and an inspection object so that the width is larger than the size of the defect. A technique for realizing narrow line-shaped illumination is disclosed (for example, see Patent Document 1).

However, since the edge portion of the emitted light cannot be used in the planar illumination device using the fluorescent lamp and the light guide plate, it is difficult to inspect the fish eye defect and the concavo-convex defect. In order to perform both the fisheye defect and the concavo-convex defect, a line-shaped illumination device is required in addition to the planar illumination device. Conversely, in the narrow line-shaped illumination disclosed in Patent Document 1, Although it is relatively easy to detect defects and uneven defects, it is not possible to quickly detect defects over the entire surface of the sheet material. In addition, an inspection by a surface illumination device is required.
For this reason, the cost of the apparatus and the maintenance cost increase, and a large space is required for installing the apparatus, which contributes to an increase in manufacturing cost.
JP 2005-49291 A

  The present invention has been made in view of the above circumstances, and it is possible to quickly inspect a foreign object defect and a dirt defect over the entire surface of a sheet-like material, and to detect a fish eye defect and a concavo-convex defect visually with the same apparatus. An object is to provide a lighting device that is possible.

In order to solve the above problems, the present invention provides the following means.
An illuminating device according to the present invention is an illuminating device that detects defects in a film-like or sheet-like inspection object, and has a plurality of line-shaped light sources arranged in parallel with the light emission surface being in the same plane. An inspection plate made of a sheet-like plate having a light diffusing function located above the light emission surfaces of the plurality of line-shaped light sources, and the distance between the light emission surface and the inspection plate is adjustable. And an interval changing means for making it possible.

In addition, the maximum value y _H and the minimum value y _L of the distance between the light exit surface and the inspection plate are within the range represented by the following expressions.
y _H > x / (2 tan θ) + p
y _L <x / (2 tan θ) −q
p = y ₁ −y ₀
q = y ₀ −y ₂
θ: emission angle of the linear light source x: distance between light sources y ₀ of the linear light source: the light emission when edges of the emitted light from the linear light sources projected on the inspection plate 2 come into contact with each other Distance y ₁ between the surface and the inspection plate: distance y ₂ between the light exit surface and the inspection plate necessary to ensure substantially uniform luminance on the inspection plate ₂ : the inspection plate 2 The distance between the light emitting surface and the inspection plate necessary to form a sufficiently clear edge between the dark part and the bright part above

  Further, in the illumination device according to the present invention, the distance varying means is provided between a stage to which the line light source is fixed and a leg portion that supports the stage and the inspection plate, and moves the stage up and down. It is characterized by an elevating function that can move forward and backward in a direction.

  ADVANTAGE OF THE INVENTION According to this invention, the illumination apparatus which can detect a defect of a different kind with the single apparatus quickly over the whole inspection target object by visual inspection can be provided.

A lighting device 10 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the illumination device 10 according to the present invention is arranged above the light guide 1 with three lines of light guides 1 for illuminating an inspection object such as a film or a sheet. In addition, a thin plate-shaped inspection plate 2 having a function of diffusing light emitted from the light guide 1 and a lifting mechanism 5 for fixing the three-line light guide 1 and moving up and down in a vertical direction are also provided. A stage 3 and a leg 4 for holding the inspection plate 2 and the stage 3 are provided.

  The stage 3 is lowered by operating the lifting mechanism 5 of the illumination device 10 having such a configuration, and the distance between the inspection plate 2 and the light guide 1 is increased. Then, the light L1 emitted from the light guide 1 and having a constant emission angle Θ spreads as hatched in FIG. 1 in the middle of being emitted from the light guide 1 and reaching the surface of the inspection plate 2. The inspection plate 2 reaches a slightly wide range. Although the brightness of the light L1 reaching the inspection plate 2 decreases as it goes outward from the central axis of the light guide 1, the illumination device 10 is provided with the three-line light guides 1; When the emitted lights L1 overlap each other, the luminance of the light reaching the inspection plate 2 is made uniform as a whole. The light reaching the inspection plate 2 diffuses in the inspection plate 2 and illuminates the inspection object from below with a substantially uniform intensity.

Further, when the stage 3 is raised by operating the elevating mechanism 5 and the light guide 1 is brought close to the inspection plate 2 as shown by a dotted line in FIG. 1, the light L2 emitted from the light guide 1 spreads so much. It reaches the inspection plate 2 without. In this case, the bright and dark edges of the light L2 emitted from the three-line light guide 1 appear sharply on the inspection plate 2.
That is, the illumination device 10 of the present invention functions as a planar illumination device when the distance between the light guide 1 and the inspection plate 2 is increased, and when the distance between the light guide 1 and the inspection plate 2 is reduced. Functions as a line lighting device.

  The light guide 1 is a light source for irradiating light to an inspection object. As shown in FIGS. 1 and 2, a plurality of optical fibers 7 having a light emitting end face 6 having a substantially circular shape, and the light emitting end face 6 are inspected. The light guides 1 are arranged so as to face the direction of the plate 2 and be on the same plane, and the light guides 1 formed in this way or possibly plural lines are arranged on the stage 3 in parallel in parallel. Thus, the illumination part 8 is formed. The number of lines of the light guide 1 is determined by the size of the illumination device 10 and the inspection object. In the illumination device 10 of the present embodiment, a three-line light guide 1 is used.

  Here, in order for the illuminating device 10 to function as planar and line-shaped illumination, the emission angle θ of the light emitted from the ride guide 1 is preferably in the range of 20 ° to 40 °. That is, when the outgoing angle θ is smaller than 20 °, the directivity of outgoing light becomes stronger and the illuminance of the irradiated surface can be made extremely high, and the contrast of the edge portion can be made clear, while being used as planar illumination. Since it is necessary to increase the number of light guides 1 per unit area of the illumination part 8, it is necessary to enlarge the housing of the illumination device 10. On the other hand, when the emission angle is larger than 40 °, the illuminance when the light reaches the inspection plate 2 tends to be insufficient, and the edge portion becomes unclear for detection of fish eye defects and concavo-convex defects. Absent.

In order to restrict the emission angle θ to the above range, a lens may be mounted on the light guide end face 11 of each light guide 1.
In consideration of the fact that the light emitted from the light guide 1 is reduced in illuminance due to diffusion on the inspection plate 2 having a diffusion function, it is necessary to use a light source having a sufficiently high luminance in order to detect defects. For example, a halogen lamp can be used as the light source of such a light guide 1.

Here, in the state where the edges of the light emitted from each light guide 1 projected onto the inspection plate 2 abut, the distance x between the centers of the plurality of light guides 1, the distance between the light guide end surface 11 and the diffusion plate 2. The relationship between the distance y ₀ and the emission angle θ is determined by equation (1).
x / 2 = y ₀ × tan θ (1)
When the light guides 1 are arranged at the center distance x determined from the equation (1), the emitted light from each light guide 1 abuts the edges on the inspection plate 2 to form a planar illumination. Actually, the brightness of the emitted light tends to decrease as it goes outward from the central axis of the light guide 1. Therefore, in order to obtain a planar illumination that ensures substantially uniform brightness on the inspection plate 2, each light It is necessary to overlap light emitted from the guide 1.

Therefore, when the plurality of light guides 1 are arranged in parallel on the stage 3 in consideration of the overlapping of the emitted light from each light guide 1, the distance x between the centers of the light guides 1 is within the range of the formula (2). What is necessary is just to arrange | position on a stage so that it may become inside.
x <2 (y ₀ −p) × tan θ (2)
Here, p is a distance y ₁ between the light guide end surface 11 and the diffusion plate 2 that is necessary for ensuring that the light emitted from the light guides 1 overlaps and the luminance on the inspection plate 2 is substantially uniform. which is the difference between the y _0.

  The inspection plate 2 is disposed above the light guide 1 and diffuses the light emitted from the light guide 1 in the diffusion plate 2 to obtain an inspection surface with reduced brightness spots. More specifically, it is preferable to use a resin plate provided with a light diffusion function by a method such as adding a diffusion material to a transparent resin plate such as an acrylic resin.

The stage 3 has an elevating mechanism 5 that fixes each light guide 1 and moves up and down.
The elevating mechanism 5 is, for example, a rack and pinion system in which a rack is arranged along the leg 4, a pinion that meshes with the rack is provided on the stage 3, and the stage 3 is moved up and down by rotating with a motor or the like. 4, a nut member that is screwed to the stage 3 is provided on the stage 3, a lead screw system that moves the stage 3 up and down by rotating the screw with a motor or the like, a fluid cylinder disposed between the stage 3 and the inspection plate 2, etc. Consists of.

  By moving the stage 3 up and down by the lifting mechanism 5, the irradiation range can be varied by changing the distance y between the inspection plate 2 and the light guide end surface 11. The leg 4 holds the inspection plate 2 and the stage 3.

Here, in FIG. 1, when the distance x between the centers of the light guides 1 is a, the light guide end surface 11 diffuses when the light emitted from each light guide 1 abuts the edges on the inspection plate 2. The distance y ₀ between the plate 2 and the plate 2 is obtained by Expression (3) obtained by converting Expression (1).
y ₀ = a / (2 tan θ) (3)

From the equation (2), the range of y in which the illumination device 10 functions as the illumination device on the surface when the overlapping of the emitted light from each light guide 1 is considered is the range of the equation (4).
y ₁ > a / (2 tan θ) + p (4)
Further, from the equation (3), when y is in the range represented by the equation (5), the light emitted from each light guide 1 does not become planar on the inspection plate 2, but between the bright part and the dark part. The edge is formed.
y <a / (2 tan θ) (5)

However, since the emitted light from the light guide 1 in this state spreads in the middle of reaching the diffuser plate 2, the luminance is lowered. Therefore, in order to function as line-shaped illumination, the light between the bright part and the dark part is used. In consideration of the clarity of the edge, it is necessary to narrow the distance y ₂ between the light guide end face 11 and the diffusion plate 2 so as to satisfy Expression (6).
y ₂ <a / ( ₂ tan θ) −q (6)
Here, q is a distance y ₂ and y between the light guide end face 11 and the diffusion plate 2 that are necessary for the light emitted from each light guide 1 to form a sufficiently clear edge on the inspection plate 2. _This is the difference from _zero .

That is, in order to switch between planar illumination and line illumination, the distance between the centers of the light guides 1 is x, the emission angle of the emitted light of the light guide 1 is θ, and the emitted light from each light guide 1 is inspected. P is the difference between the distances y ₂ and y ₀ between the light guide end face 11 and the diffusion plate 2 that are necessary to ensure a substantially uniform brightness on the inspection plate 2 and overlapping on the inspection plate 2. The difference between the distances y ₂ and y ₀ between the light guide end face 11 and the diffusion plate 2 required for the light emitted from the guide 1 to form a sufficiently clear edge on the inspection plate 2 is defined as q. Sometimes, the maximum value y _H and the minimum value y _L of the distance between the inspection plate 2 and the light guide end surface 11 obtained by moving the inspection plate 2 up and down by the elevating function 5 are in the ranges represented by the following equations, respectively. It is necessary to be.
x / (2 tan θ) + p <y _H and y _L <x / (2 tan θ) −q (6)

Here, when y is in the range of the expression (7), the uniformity of the luminance on the inspection plate 2 may be insufficient, or the clarity of the edge between the bright part and the dark part may be insufficient. is there.
x / (2 tan θ) + p>y> x / (2 tan θ) −q (7)

Below, a suitable example of the illuminating device 10 concerning this invention is shown.
As the inspection plate 2, a 2.0 mm thick milky white acrylic resin diffusion plate (Acrylite manufactured by Mitsubishi Rayon Co., Ltd.) having titanium oxide added as a light diffusion material inside was used.
As the light guide 1, an optical fiber light guide (PL300-1000 manufactured by Mitsubishi Rayon Co., Ltd.) having a configuration in which many plastic optical fibers 7 are bundled is used. This optical fiber light guide is set to have an emission width of 300 mm and an emission angle of 30 degrees.
As a light source of the optical fiber light guide, a halogen lamp light source device using a 100 W halogen lamp (halogen lamp light source device ELI-100G manufactured by Mitsubishi Rayon Co., Ltd.) was used.

  In FIG. 4, the illumination device 10 having the above-described configuration is used, the distance y between the light guide end surface 11 and the inspection plate 2 is set to 150 mm, the distance x between the light guides 1 is set to 100 mm, and the inspection plate 2 is placed on the upper surface. 5 is a graph showing the relative luminance when captured by a line CCD camera (resolution: 0.1 mm / pixel).

  When the distance y between the light guide end face 11 and the inspection plate 2 is 150 mm, the visual field position with the maximum luminance is a position of about 45 mm (“A” in FIG. 3) near the center of the axis of the light guide 1. The visual field position of the minimum luminance between the light guides 1 is about 90 mm near the middle between the light guides 1 (“B” in FIG. 3), and the relative luminance is 0.85 with respect to the maximum luminance of 1.0. It was. The minimum brightness is about 15% lower than the maximum brightness. This difference can be used as a uniform surface illumination device for visual inspection without any problem, and is capable of quickly inspecting the entire surface without moving the inspection object in the inspection of foreign matter defects and dirt defects.

  In this state, when the visual inspection of the foreign matter defect and fish eye defect of the transparent acrylic resin sheet was actually performed using the lighting device 10, the foreign matter defect could be confirmed at any position on the sheet. Fish eye defects could not be confirmed.

FIG. 5 is a graph of relative luminance when the stage 3 is raised so that the distance y between the light guide end face 11 and the inspection plate 2 is 30 mm.
When the distance y between the light guide end face 11 and the inspection plate 2 is 30 mm, the illumination width of the light guide 1 is about 65 mm (see FIG. 4) from the visual field position 20 mm (“A” in FIG. 4) of the line CCD camera. “C”), and the illumination width is about 45 mm. The maximum luminance is a position (“B” in FIG. 4) of about 45 mm in the center position of the illumination width. The luminance decreases by about 4.5% per mm until the relative luminance becomes 0 from the maximum luminance. If there is this difference, it is possible to sufficiently detect fish eye defects and irregularities as the edge portions between the bright and dark portions of the illumination.
When the same transparent acrylic resin sheet as described above was visually inspected by the lighting device 10, the presence of fish eye defects could be confirmed at the edge of the lighting.

  As described above, according to the illuminating device 10 according to the present embodiment, the position of the plurality of light guides 1 is raised and lowered so that the distance between the inspection plate 2 and the light guide end surface 11 can be adjusted. The distance between the light guide end face 11 and the light guide 1 can be reduced so that the light emitted from each light guide 1 is projected onto the inspection plate 2 so that the edges of the bright and dark portions are sharply formed. The distance between the light guide 1 and the light guide 1 is increased, and the light emitted from the adjacent light guides 1 is uniformly diffused by the inspection plate 2 while being superimposed, so that the inspection plate 2 can be brightened over the entire surface, so that the line illumination Can be switched between the state of light and the state of planar illumination, and the function to inspect foreign matter defects and dirt defects over the entire surface and the function to inspect fish eye defects and uneven defects can be realized with one unit . And while reducing the manufacturing cost by the expense and maintenance cost of an apparatus, the space for apparatus installation can be reduced.

Further, by changing the stage 3 to which the light guide 1 is fixed within the range of the expression (6), foreign matter defects and dirt defects in the state of planar illumination, fish eye defects and unevenness defects in the state of line illumination, Inspection can be performed with high sensitivity.
Furthermore, since the position of the inspection plate 2 is fixed and the state of the planar illumination and the state of the line illumination can be switched, the inspection of the foreign object defect and the dirt defect and the fish can be performed without changing the height of the inspection object. Inspection of eye defects and irregularities can be performed, and inspection efficiency can be increased.

  In this embodiment, the inspection plate 2 is installed horizontally in the horizontal direction. However, the inspection plate 2 is not limited to the horizontal direction, and may be installed in a vertically standing state, for example.

  In this embodiment, the stage 3 is moved to change the distance between the light guide end face 11 and the inspection plate 2. However, the inspection plate 2 may be moved up and down, or the inspection plate 2 and the stage 3 Both may be raised and lowered.

It is a longitudinal cross-sectional view which shows one Embodiment of the illuminating device based on this invention. It is a figure which shows the light guide used for this invention. It is a graph showing the relationship between the visual field position and relative luminance when the distance between the light guide end surface and the diffusion plate is 150 mm and the diffusion plate is imaged from the upper surface with a CCD camera. It is the graph showing the relationship between a visual field position and relative brightness | luminance when arrange | positioning the distance between a light guide end surface and a diffusion plate to 30 mm, and imaging a diffusion plate with a CCD camera from the upper surface. This is a conventional general surface illumination device using a fluorescent lamp.

Explanation of symbols

1 Light guide (Line light source)
2 Inspection plate 3 Stage 4 Leg 5 Lift mechanism 6 Light exit end face 7 Optical fiber 8 Illumination portion 10 Illumination device 11 Light guide end face (light exit face)

Claims (3)

An illumination device for detecting defects in a film-like or sheet-like inspection object,
A plurality of line-shaped light sources arranged in parallel with the light emission surface being on the same plane;
An inspection plate made of a sheet-like plate located above the light emitting surface of the plurality of line-shaped light sources and having a light diffusion function;
An illuminating device comprising: an interval variable unit that adjustably changes a distance between the light emitting surface and the inspection plate. Maximum y _H, and the minimum value y _L of the distance between the test plate and the light exit surface, the illumination device according to claim 1, characterized in that within the scope of the following equation.
y _H > x / (2 tan θ) + p
y _L <x / (2 tan θ) −q
p = y ₁ −y ₀
q = y ₀ −y ₂
θ: emission angle of the linear light source x: distance between light sources y ₀ of the linear light source: the light projected on the inspection plate 2 when the edges of the emitted light from the linear light sources come into contact with each other Distance y ₁ between the exit surface and the inspection plate: Distance y ₂ between the light exit surface and the inspection plate necessary to ensure substantially uniform brightness on the inspection plate ₂ : The inspection plate 2 The distance between the light emitting surface and the inspection plate necessary to form a dark and bright edge sufficiently clear on 2 The interval varying means is provided between a stage to which the line-shaped light source is fixed and a leg portion that holds the stage and the inspection plate, and has a lifting function for moving the stage in a vertically movable manner. The lighting device according to claim 1, wherein the lighting device is provided.

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