Lighting device

Abstract

To provide a lighting device capable of increasing an amount of light reaching a line sensor without causing reflection of a light source or the like, and further capable of saving a space, while maintaining advantages of dome lighting as much as possible.SOLUTION: A lighting device comprises a plurality of light sources 10, 20 or light-emitting surfaces, and a light guide plate 30 into which light from the plurality of light sources 10, 20 or the light-emitting surfaces is made incident from an end surface. One surface of the light guide plate 30 in a thickness direction is provided with a plurality of reflective units 31 that reflects the light incident from the end surface toward an irradiation position facing the light guide plate 30. Also, a reflective member is in contact with or adjacent to the portion of the one surface of the light guide plate 30 in the thickness direction other than an observation window.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a lighting device.

Background Art

[0002] A technique for illuminating an imaging line (observation position) of a line sensor with a dome-shaped lighting device is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the dome-shaped lighting device of Patent Document 1, a slit along the longitudinal direction of the line sensor is provided at the upper end of the reflection dome, and an object arranged below the reflection dome through the slit is observed by the line sensor. With the dome-shaped lighting device, light is irradiated from various directions to the observation position of the line sensor. Therefore, there is an advantage that the shadowed portion of the object can be reduced as much as possible.

[0005] Further, a slit is provided at the upper end of the reflection dome, and the line sensor is arranged directly above the slit. Therefore, even when an object such as a flat plate having a mirror-like upper surface is the target, there is an advantage that the inner surface of the reflection dome or an LED serving as a light source does not reflect on the mirror-like upper surface of the object when viewed from the line sensor.

[0006] However, when viewed from the line sensor, a state where the inner surface of the reflection dome, an LED serving as a light source, etc. do not appear on the upper surface of the object that is a mirror surface is also a state where it is difficult for the light from the reflection dome to reach the line sensor. That is, since there is a slit at the upper end of the reflection dome, light is obliquely irradiated from the reflection dome to the observation position of the line sensor, and the obliquely irradiated light is specularly reflected by the upper surface of the object that is a mirror surface. For this reason, the amount of light may be insufficient when observing the object with the line sensor.

[0007] In addition, in order to supply a sufficient amount of light to the object from various directions, the reflection dome may be enlarged.

[0008] The present invention has been made in view of such circumstances, and even when observing an object having an upper surface that is a mirror surface with a line sensor while maintaining the advantages of dome-shaped illumination as much as possible, it is possible to increase the amount of light reaching the line sensor without causing reflection of a light source or the like, and moreover, an object of the present invention is to provide an illumination device capable of saving space.

Means for Solving the Problem

[0009] In order to solve the above problems, an illumination device according to an aspect of the present invention includes a plurality of light sources arranged in parallel in the X direction or a light emitting surface having a longitudinal direction in the X direction, and a light guide plate having a longitudinal direction in the X direction and through which light from the plurality of light sources or the light emitting surface enters from an end surface in a Y direction orthogonal to the X direction. On one surface in the thickness direction of the light guide plate, a plurality of reflecting portions are provided for reflecting the light entering from the end surface toward an irradiation position facing the light guide plate. The light guide plate is provided with an observation window that enables the irradiation position to be observed with a line sensor through the light guide plate, and the observation window has a longitudinal direction in the X direction. A first ratio, which is a ratio of an area where the reflecting portion of the observation window is provided to an entire area of the observation window, is 2% or more, and a second ratio, which is a ratio of an area where the reflecting portion is provided in another portion of the light guide plate other than the observation window to an entire area of the other portion, is 1.2 times or more the first ratio.

[0010] In this aspect, since a reflective portion is also provided on the observation window, when observing an object through the observation window with a line sensor, the object is irradiated with light from the observation window as well. That is, the light supplied from the observation window to the object becomes the light supplied in the observation direction of the line sensor toward the object. Therefore, when observing an object having a shiny upper surface such as a mirror surface with a line sensor, the amount of light supplied from the object to the line sensor increases compared to the conventional dome-shaped illumination. In addition, light is supplied from the reflective portion of other parts other than the observation window to the object, and light is supplied to the observation position by the line sensor from various directions.

Advantages of the Invention

[0011] According to the present invention, while maintaining the advantages of the dome-shaped illumination as much as possible, when observing an object having a shiny upper surface such as a mirror surface with a line sensor, it is possible to increase the amount of light reaching the line sensor without causing reflection of a light source or the like, and moreover, space can be saved.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0013] A lighting device according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 7. As shown in FIG. 2, this lighting device illuminates an object W to be observed (inspected) etc. by a line sensor S. As shown in FIG. 1, this lighting device has a plurality of first light sources 10 arranged in a predetermined direction (the X direction in FIG. 1) and a plurality of second light sources 20 arranged in the predetermined direction. In this embodiment, each of the light sources 10 and 20 is an LED element such as a chip-type LED or a bullet-type LED. The plurality of light sources 10 are arranged at intervals in the X direction, and the interval is several millimeters, more than ten millimeters, etc. The plurality of light sources 20 are also arranged at intervals in the X direction. In one example, as shown in FIG. 2, the object W is conveyed in the Y direction orthogonal to the X direction by a conveyor CV.

[0014] This lighting device includes a light guide plate 30 into which light from the plurality of first light sources 10 and light from the plurality of second light sources 20 are incident. In this embodiment, the light guide plate 30 is a flat plate of transparent plastic. The material of the light guide plate 30 may be other well-known materials such as glass. As shown in FIG. 1, in this embodiment, the predetermined direction is referred to as the X direction, and the direction orthogonal to the X direction and in which the light guide plate 30 extends is referred to as the Y direction. Also, as shown in FIGS. 1 and 2, the direction orthogonal to the X direction and the Y direction is referred to as the Z direction.

[0015] Light from the plurality of first light sources 10 enters the light guide plate 30 from one end face 30a in the Y direction of the light guide plate 30, and light from the plurality of second light sources 20 enters the light guide plate 30 from the other end face 30b in the Y direction of the light guide plate 30. As shown in FIGS. 2 and 5, the plurality of first light sources 10 are attached to a first body 11, and the plurality of second light sources 20 are attached to a second body 21.

[0016] In one example, a plurality of first light sources 10 are attached to one end surface of the first body 11 on the side of the light guide plate 30 in the Y direction. Further, on the one end surface side of the first body 11, a pair of protruding portions 11a protruding in the Y direction are provided. The pair of protruding portions 11a are arranged at intervals in the Z direction from each other, and one end portion of the light guide plate 30 in the Y direction is arranged between the pair of protruding portions 11a. In the present embodiment, each protruding portion 11a is provided over substantially the entire Y direction of the first body 11. The light guide plate 30 is positioned with respect to the first body 11 at least in the Z direction by the pair of protruding portions 11a.

[0017] A plurality of second light sources 20 are attached to one end surface of the second body 21 on the side of the light guide plate 30 in the Y direction, and a pair of protruding portions 21a similar to the first body 11 are also provided on the second body 21. As shown in FIGS. 2 and 4, heat dissipation portions 11b and 21b are formed at end portions of the first body 11 and the second body 21 in the Y direction on the side opposite to the light guide plate 30.

[0018] As shown in FIGS. 1, 3, and 5, fixing members 40 are attached to one end and the other end of the first and second bodies 11 and 21 in the X direction, respectively. One fixing member 40 is fixed to one end of the first body 11 in the X direction by a fastening member 41 such as a bolt, and is also fixed to one end of the second body 21 in the X direction by the fastening member 41. Further, the other fixing member 40 is fixed to the other end of the first body 11 in the X direction by the fastening member 41, and is also fixed to the other end of the second body 21 in the X direction by the fastening member 41. Each fixing member 40 restricts the movement of the light guide plate 30 in the X direction and connects the first body 11 and the second body 21. With this configuration, the light guide plate 30 can be easily and surely attached to the first and second bodies 10 and 20. With the above configuration, it is possible to easily and surely manufacture this lighting device having different dimensions in the X direction, which is useful for flexibly responding to various customer requirements such as inspection objects and inspection conditions.

[0019] As shown in FIG. 6, a plurality of reflecting portions 31 are provided on one surface 30c in the thickness direction of the light guide plate 30. In the present embodiment, each reflecting portion 31 is a convex lens protruding from the one surface 30c. FIG. 6 shows one of the ideal shapes of each reflecting portion 31. As shown in FIG. 6, each reflecting portion 31 reflects the light from each light source 10, 20 in the light guide plate 30 toward the irradiation position facing the light guide plate 30 through the other surface 30d in the thickness direction of the light guide plate 30. Note that FIG. 6 is a schematic diagram for illustrating the function of the reflecting portion 31, and in FIG. 6, the thickness dimension of the light guide plate 30 is drawn smaller than the size of the reflecting portion 31.

[0020] Each reflecting portion 31 can be formed, for example, by inkjet printing using a transparent ultraviolet curable plastic. The plurality of reflecting portions 31 are arranged at intervals DT in the X direction and the Y direction respectively, and the interval DT is, for example, 85 μm.

[0021] In the present embodiment, as shown in FIGS. 1 and 2, the central side in the Y direction of the light guide plate 30 functions as an observation window 32, and the observation window 32 has a longitudinal direction in the X direction. In the present embodiment, the observation window 32 is provided over the entire X direction of the light guide plate 30, but the range of the observation window 32 in the X direction only needs to correspond to the observation range of the line sensor. The dimension of the observation window 32 in the Y direction is preferably 2 cm or less, but in the present embodiment, the dimension of the observation window 32 in the Y direction is 1 cm or less.

[0022] The plurality of reflecting portions 31 are also provided on the observation window 32. The first diameter (diameter D shown in FIG. 6) of the observation window 32 is preferably 41 μm or less, more preferably 36 μm or less, and is 32 μm in the present application. That is, in the observation window 32, preferably, the first ratio, which is the ratio of the area where the reflecting portion 31 is provided to the entire area of the observation window 32, is preferably 18% or less. The first ratio is more preferably 14% or less, and is about 11% in the present embodiment. If the first ratio is higher than the above ratio, when observing the object W through the observation window 32 by the line sensor as shown in FIG. 2, the obtained image may become unclear. Note that the first ratio is preferably 2% or more. When the first ratio is less than 2%, the effects described below are often not obtained, but there are cases where it can be used depending on the observation conditions, the object, etc. In the present embodiment, the reflecting portions 31 of the observation window 32 are provided evenly, but there may be a bias in the distribution of the reflecting portions 31.

[0023] Here, when forming each reflecting portion 31, there may be a portion that hardly functions as a convex lens for directing the light to the irradiation position. For example, as shown in FIG. 7, when a part 31a of the reflecting portion 31 is thinly formed along the one surface of the light guide plate 30 and the part 31a is substantially flat, it hardly functions as the convex lens. In this case, as shown in FIG. 7, the area of the portion AR of the convex lens for directing the light to the irradiation position is used in the calculation of the first ratio. The same calculation is performed for the following second ratio. Also, as shown in FIG. 7, even when there are single or a plurality of specific portions 31b having different shape characteristics from other portions in the reflecting portion 31, or when the entire reflecting portion 31 is not a smooth convex lens, if it has a function of directing the light to the irradiation position as a whole, it can be said to be the reflecting portion 31.

[0024] On the other hand, the second ratio, which is the ratio of the area where the reflecting portion 31 is provided in the other portion 33 other than the observation window 32 of the light guide plate 30 to the entire area of the other portion 33, is preferably 1.5 times or more, more preferably 2 times or more, with respect to the first ratio. When the first ratio is 10% or more, for example, if the second ratio is 1.2 times or more with respect to the first ratio, the effects described below may be achieved. In the present embodiment, since the diameter of each reflecting portion 31 of the observation window 32 is 32 μm, the second diameter (diameter D shown in FIG. 6) of each reflecting portion 31 is preferably 45 μm or more. In the present embodiment, the second diameter is 62 μm, and the second ratio is about 42%. The lighting device can be realized if the second ratio is 5% or more, preferably 15% or more. When increasing the amount of light more, it is preferably 20% or more, and when further increasing the amount of light, it is preferably 25% or more. Even if the second ratio is less than 15%, there may be cases where inspection can be performed without problems depending on the purpose of observation or the like. In the present embodiment, the reflecting portions 31 of the other portion 33 are provided evenly, but there may be cases where the distribution of the reflecting portions 31 is biased. In the present embodiment, the dimension in the Y direction of the other portion 33 is 5 cm or more, but if the distance to the irradiation position is small, the same effect may be obtained if the dimension in the Y direction of the other portion 33 is 1 cm or more.

[0025] Note that there may be cases where the reflecting portions 31 are not uniformly distributed and it is difficult to confirm the ratio of the entire observation window 32 or the entire other portion 33. In this case, for the first ratio, the ratio of the area of the reflecting portion 31 to the area of the relevant portion can be obtained at each of a plurality of locations of the observation window 32, and the average of the ratios obtained at the plurality of locations can be set as the first ratio. The same applies to the second ratio. Also, it is possible to change the first ratio and the second ratio according to the interval DT between the reflecting portions 31.

[0026] As shown in FIG. 2, a known line sensor S is disposed on the one surface 30c side of the light guide plate 30 to obtain an image of an object W at an irradiation position on the other surface 30d side of the light guide plate 30. The line sensor S is naturally disposed along the observation window 32.

[0027] When the lighting device having the above configuration is used, the amount of light reaching the line sensor S increases. In particular, light is also irradiated from the observation window 32 toward the irradiation position. The light from the light sources 10 and 20 travels through the light guide plate 30 along the light ray trajectories L1, L2, L3, and L4 shown in FIG. 6, and a part of the light ray trajectories L1, L2, L3, and L4 is reflected by the reflecting portion 31 toward the irradiation position. A part L4 of them travels substantially perpendicular to the other surface 30d of the light guide plate 30. "Substantially perpendicular" means that, for example, the angle formed by the other surface 30d and the light ray L4 is 80° or less, more preferably 85° or less. When the light guide plate 30 is made of a plastic material, the critical angle is 45° or less, and the light that enters the reflecting portion 31 at an angle exceeding the critical angle is reflected.

[0028] In this way, when the light reflected by the observation window 32 travels substantially perpendicular to the other surface 30d of the light guide plate 30, observation, inspection, etc. using the line sensor S may be accurate when the object W is a shiny object. Also, when an electronic component or the like protrudes from the surface of the object W, it is difficult to form a shadow due to the electronic component. Thus, the present embodiment is effective in reducing the change in the illuminance of the observation line due to the shape and gloss of the surface of the object W.

[0029] Also, since light is reflected toward the object W at the position of the observation window 32, the amount of light reaching the line sensor S increases with respect to various types of objects W, which is advantageous in aiming for high-speed inspection and improved inspection accuracy. Also, unlike the case where the reflecting portion 31 is not provided in the observation window 32, light is also irradiated onto the object W from the direction along the optical axis of the line sensor S, and the image obtained by the line sensor S is different from the case where the reflecting portion 31 is not provided in the observation window 32. This results in a difference in the brightness and appearance of the object W in the image, which leads to improved inspection accuracy depending on the type of the object W.

[0030] Also, the light from the other portion 33 is also irradiated onto the observation position by the line sensor S. For this reason, the object W at the observation position (irradiation position) is irradiated from various directions, and the same effect as that of the conventional dome-shaped illumination can be obtained. That is, the same effect as that of the dome-shaped illumination can be realized with space saving.

[0031] When the second ratio is 1.5 times or more the first ratio, the observation of the object W can be performed well in terms of the balance of the irradiation amount of light from the optical axis direction of the line sensor S, the irradiation amount of light from the other part 33, and the sharpness of the image obtained by the line sensor S. Note that, as in the present embodiment, when the second ratio is 2.5 times or more or 3 times or more the first ratio, the observation of the object W often becomes better. In addition, when the first ratio is 10% or more, if the second ratio is 1.2 times or more the first ratio, the absolute value of the difference between the first ratio and the second ratio becomes 2% or more. Also in this case, the observation of the object W often becomes better.

[0032] Note that the position of the observation window 32 in the light guide plate 30 can be arbitrarily set. For example, it is also possible to provide the observation window 32 on one end side in the Y direction of the light guide plate 30 and provide the other part 33 only on the other end side in the Y direction with respect to the observation window 32. Or, it is also possible to provide the observation window 32 on one end side in the Y direction of the light guide plate 30 and provide the other part 33 on both sides in the Y direction with respect to the observation window 32. These arrangements are effective when the object W can be seen better when irradiated with more light from one side.

[0033] Also, it is possible to provide a plurality of observation windows 32 in the light guide plate 30 at intervals in the Y direction. Also, the second ratio of the other part 33 on one side in the Y direction with respect to the observation window 32 and the second ratio of the other part 33 on the other side in the Y direction may be made different. For example, the second ratio of one side may be 1.2 times or more, preferably 1.5 times or more the second ratio of the other side. This configuration is useful when inspecting an object W that is easier to observe when the light from one side in the Y direction is strengthened.

[0034] Furthermore, a structure in which the lighting device has a plurality of types of light guide plates 30 and the light guide plates 30 can be replaced with other types of light guide plates 30 according to the inspection object is useful. In the present embodiment, the light guide plate 30 can be replaced by attaching and detaching the fixing member 40.

[0035] Also, it is also possible to configure such that the density of the reflecting portion 31 of the other portion 33 gradually increases toward the observation window 32 side. In this case, in the other portion 33, the amount of light traveling from the vicinity of the observation window 32 toward the irradiation position increases. It is also possible to distribute the reflecting portion 31 in other modes in the other portion 33. In the other portion 33, it is also possible to make the density of the reflecting portion 31 closer to the observation window 32 higher than the density of the reflecting portion 31 farther from the observation window 32. In this case, even if the reflecting portion 31 is not provided on the observation window 32, the amount of light traveling from the line sensor S side toward the irradiation position increases. When using such a configuration, depending on the object W, the observation purpose, etc., it may be possible to perform good observation of the object W.

[0036] Note that, as shown in FIG. 8, it is also possible to provide a reflecting portion 34, which is a concave portion, on one surface 30c in the thickness direction instead of the reflecting portion 31. Even in this case, each reflecting portion 34 reflects the light from the light sources 10, 20 toward the irradiation position. The reflecting portion 34 can be a conical concave portion, a pyramidal concave portion, a concave portion having a shape of a part of a spherical surface, or other shaped concave portions. Also, each reflecting portion 31 can be formed by attaching a reflecting member such as a small metal member to one surface 30c in the thickness direction of the light guide plate 30.

[0037] Also, it is also possible to bring a reflecting sheet into contact with or close to one surface 30c in the thickness direction of the other portion 33, together with the reflecting portions 31, 34 or without providing the reflecting portions 31, 34. The reflecting sheet may be a known sheet that reflects light, such as a white sheet such as paper or a sheet having a metallic luster such as aluminum foil. When the reflecting portions 31, 34, irregularities due to rough surface treatment, etc. are provided on the other portion 33 on one surface 30c in the thickness direction and light entering from the end surfaces 30a, 30b leaks from one surface 30c in the thickness direction, the same operational effects as when the reflecting portions 31, 34 are provided on the other portion 33 can be achieved. When a reflecting sheet is provided together with the reflecting portions 31, 34, etc. on the other portion 33, the amount of light at the irradiation position increases.

[0038] Alternatively, instead of the plurality of first light sources 10, a light emitting surface may be provided along the end face 30a of the light guide plate 30 to introduce light into the light guide plate 30 from the end face 30a. The light emitting surface may be another light guide plate arranged along the end face 30a. In this case, light is introduced into the other light guide plate, and the light is emitted from the surface along the end face 30a of the other light guide plate. A similar light emitting surface may be provided instead of the plurality of second light sources 10. Further, each of the first light sources 10, 20 may be the tip of an optical fiber.

[0039] Note that there is also a lighting device including a plurality of light sources 10, 20 arranged side by side in the X direction or a light emitting surface having a longitudinal direction in the X direction, and a light guide plate 30 having a longitudinal direction in the X direction and configured such that light from the plurality of light sources 10, 20 or the light emitting surface is incident on end faces 30a, 30b in the Y direction orthogonal to the X direction. On one surface in the thickness direction of the light guide plate, a plurality of reflecting portions 31, 34 are provided to reflect the light incident on the end face toward the irradiation position facing the light guide plate. The light guide plate 30 is provided with an observation window 32 that enables the irradiation position to be observed with a line sensor S and has a longitudinal direction in the X direction. The reflecting portions 30a, 30b are not provided on the observation window, and the reflecting portions 31, 34 are provided on other portions 33 of the light guide plate 30 other than the observation window 32. The area where the reflecting portions 31, 34 are provided on the other portions 33 conforms to the aforementioned second ratio. That is, the area where the reflecting portions 31, 34 are provided on the other portions 33 is 10% or more of the total area of the other portions 33. Further, it is also possible to form the observation window 32 by cutting out a portion of the light guide plate 30 corresponding to the observation window 32. Also in this case, depending on the object W, the purpose of observation, etc., it may be possible to observe the object W well. Also in this case, the object W at the observation position (irradiation position) is irradiated from various directions, and the same effect as that of the conventional dome-shaped illumination can be obtained. That is, the same effect as that of the dome-shaped illumination can be realized in a space-saving manner.

Description of Reference Numerals

[0040] 10…First light source, 20…Second light source, 30…Light guide plate, 30a…One end face in the Y direction, 30b…The other end face in the Y direction, 31…Reflection part, 32…Observation window, 33…Other part, 34…Reflection part, S…Line sensor, W…Object

Claims

1. A plurality of light sources arranged in the X direction or a light emitting surface having a longitudinal direction in the X direction, A light guide plate having a longitudinal direction in the X direction and into which light from the plurality of light sources or the light emitting surface enters from an end surface in the Y direction orthogonal to the X direction, On one surface of the light guide plate in the thickness direction, a plurality of reflecting portions are provided for reflecting the light entering from the end surface toward an irradiation position facing the light guide plate, The light guide plate is provided with an observation window that enables the irradiation position to be observed with a line sensor through the light guide plate, and the observation window has a longitudinal direction in the X direction, A first ratio, which is a ratio of an area where the reflecting portion of the observation window is provided to an entire area of the observation window, is 2% or more, A second ratio, which is a ratio of an area where the reflecting portion is provided in another portion other than the observation window in the light guide plate to an entire area of the other portion, is 1.2 times or more the first ratio. A lighting device.

2. The second ratio is 5% or more. The lighting device according to claim 1.

3. Each of the reflecting portions is a lens protruding from the light guide plate. The lighting device according to claim 1 or 2.

4. The lighting device according to any one of claims 1 to 3, further comprising a reflective sheet that contacts or is close to the other portion of the one surface in the thickness direction.

Images