JP2021085808A - Light irradiation device - Google Patents

Abstract

To further improve a light quantity and uniformity in a flat plate type omnidirectional light irradiation device.SOLUTION: A light irradiation device is constituted such that light from a light source 2 enters the inside of a lightguide plate 1 from its side face 1c, is reflected on one plate surface 1a of the lightguide plate 1, emitted to the outside from the other plate surface 1b of the lightguide plate 1 and radiated to a prescribed object W, the object W being observable through the lightguide plate from the one plate surface 1a side of the lightguide plate 1. A light source arrangement region S1 extending in the longitudinal direction and a light source non-arrangement region S2 outward of the light source arrangement region S1 in the longitudinal direction are provided on a substrate 3, a length L2 along the longitudinal direction of the light source non-arrangement region S2 being equal to a prescribed pitch p or longer.SELECTED DRAWING: Figure 5

Description

The present invention relates to a light irradiating device that irradiates light for surface inspection of a product or the like.

Conventionally, an object (hereinafter, also referred to as a work) such as a product is irradiated with light as uniform as possible from all directions to inspect the object (hereinafter, omnidirectional light irradiation device). Also known as). Such an omnidirectional light irradiation device does not create a shadow due to a curved surface or unevenness on the inspection site of the work, and can make, for example, the printing on the work surface or the difference in color stand out. Suitable for inspection of R-shaped workpieces, solder parts, etc.

A dome-shaped light emitting device is widely known as such an omnidirectional light irradiation device, but since the height dimension is slightly large, recently, as shown in Patent Document 1, a flat plate rectangular light guide plate is used. A thin flat plate type omnidirectional light irradiation device has been developed.

This type of flat plate type omnidirectional light irradiation device includes a flat plate rectangular light guide plate, a substrate arranged so as to face each side surface of the light guide plate, and a plurality of LEDs arranged in a row on the substrate. , A frame body that accommodates these LEDs and a substrate and supports the peripheral edge of the light guide plate is provided.

A large number of fine diffuse reflection portions are provided on one surface of the light guide plate with a gap from each other. As a result, the light emitted from the light source and incident on the inside of the light guide plate from the side surface is repeatedly totally reflected between the opposing plate surfaces of the light guide plate to proceed, and the light hits the diffuse reflection portion. The light is reflected and emitted to the outside from the other plate surface of the light guide plate, that is, only the other plate surface of the light guide plate is made to emit light in a planar manner. The term "diffusion" as used herein also includes a mode in which light spreads by being reflected by, for example, a spherical surface.

In the configuration in which the other plate surface of the light guide plate is made to emit light, the light emitted to the outside passes through the other plate surface of the light guide plate inside the frame supporting the peripheral edge of the light guide plate. It is the coming light.

For this reason, when trying to improve the amount and uniformity of the light passing through the inside of the frame, the light guide plate masked by the frame is used in the conventional fixed concept and technical common sense in the present technical field. We have not paid attention to the peripheral structure of the peripheral part of.

Japanese Unexamined Patent Publication No. 2003-98093

Under these circumstances, the inventor of the present application puts the corners of the four corners masked on the frame in the flat plate rectangular light guide plate in order to further improve the light intensity and uniformity in the above-mentioned flat plate type omnidirectional light irradiation device. Focusing for the first time, we found that there is room for further improvement in the peripheral structure at these corners.

That is, the light irradiation device according to the present invention includes a flat plate rectangular light guide plate, a substrate facing each side surface of the light guide plate, a plurality of light sources arranged on the substrate at a predetermined pitch, the light source, and the substrate. A frame body that accommodates and supports the peripheral edge of the light guide plate is provided, and light from the light source enters the inside of the light guide plate from the side surface and is reflected by one plate surface of the light guide plate. , It is configured so that it is ejected from the other plate surface of the light guide plate to the outside to irradiate a predetermined object, and the object can be observed from one plate surface side of the light guide plate through the light guide plate. It was done.

In the light irradiation device according to the present invention, the substrate is provided with a light source arrangement region extending in the longitudinal direction and a light source non-arrangement region outside the light source arrangement region in the longitudinal direction, and the light source non-arrangement region is provided. The region is characterized in that the length along the longitudinal direction is equal to or greater than the predetermined pitch.

According to the light irradiation device configured in this way, the length of the light source non-arrangement region along the longitudinal direction is at least a predetermined pitch, and a substrate that is longer in the longitudinal direction than the conventional substrate is used. The substrate can be extended to the corners of the light guide plate. As a result, it is possible to reduce the amount of light incident on the inside of the light guide plate, reaching the corner portion, and leaking light from the corner portion. As a result, the efficiency of light utilization is improved, and the amount and uniformity of light emitted to the outside can be improved more than before.

It is preferable that the reflectance of the light source non-arranged region is higher than that of the light source arranged region.
In this case, the light leaking from the corners of the light guide plate can be reflected toward the side surface of the light guide plate in the area where the light source is not arranged and then incident on the inside of the light guide plate again, so that the amount of light emitted to the outside can be reflected. And the uniformity can be further improved.

As a more specific reflectance, it is preferable that the reflectance of the light source non-arranged region is 50% or more.

As a specific mode for reflecting the light leaked from the light guide plate as described above, a mode in which a white solder resist layer is formed at least in the light source non-arranged region on the substrate can be mentioned.

When the white solder resist layer is used as described above, it is preferable that the white solder resist layer is formed in the light source arrangement region and the light source non-arrangement region in the substrate.
In this case, for example, by extending a conventional substrate on which a white solder resist layer is formed, a substrate provided with a light source non-arrangement region can be easily manufactured, and as a result, the number of parts of this light irradiation device can be increased. It is possible to manufacture the product without increasing the cost.

Further, as another specific embodiment for reflecting the light leaked from the corner portion of the light guide plate, an embodiment in which a solder leveler is provided in the light source non-arrangement region of the substrate can be mentioned.

It is preferable that the light source non-arranged region faces the side surface of the light guide plate and allows light to pass between them without being blocked.
In these cases, the light leaking from the corners can be reliably reflected by the side surface of the light guide plate.

According to the present invention configured as described above, the amount of light and the uniformity of the flat plate type omnidirectional light irradiation device can be improved as compared with the conventional case.

It is a perspective view which shows the inspection system including the light irradiation apparatus in this embodiment. It is a vertical sectional view of the light irradiation apparatus in the same embodiment. It is a top view seen from one plate surface side of the light guide plate in the same embodiment. It is a simplified plan view which shows the structure of the light guide plate and the substrate in the same embodiment. It is a schematic diagram which shows the light source arrangement area and the light source non-arrangement area in the same embodiment. It is a perspective view which shows the light source non-arrangement region in the same embodiment. It is a schematic diagram for demonstrating the phenomenon when the light source is arranged in the light source non-arrangement area. It is a perspective view for demonstrating the light leakage from the corner part of the substrate in the conventional structure. It is a perspective view which shows the light source non-arrangement region in other embodiment.

Hereinafter, an embodiment of the light irradiation device according to the present invention will be described with reference to the drawings.

<Device configuration>
As shown in FIG. 1, the light irradiation device 100 of the present embodiment has a thin flat plate rectangular shape as a whole, and as described in the background art, almost all of the work W, which is the object to be inspected. By irradiating light as uniform as possible from the direction (almost 180 ° all-sky direction), it has a function of canceling shadows due to curved surfaces and slight irregularities on the surface of the work W.

More specifically, as shown in FIGS. 1 and 2, the light irradiation device 100 includes a flat light guide plate 1, a plurality of LEDs 2 as light sources arranged around the light guide plate 1, and an LED 2. A substrate 3 is provided so as to face each side surface of the light guide plate 1, and a frame body 4 that accommodates the LED 2 and the substrate 3 and supports the peripheral edge of the light guide plate 1.

As shown in FIG. 3, the light guide plate 1 is, for example, a transparent plate made of resin (here, made of PMMA) having an equal thickness and forming a square shape or a rectangular shape. Then, as shown in FIG. 2, a diffuse reflection portion 5 for reflecting light is formed on one of the parallel plate surfaces facing each other, and the other plate surface 1b is formed on a smooth mirror surface. It is done.

The diffuse reflection unit 5 diffuses the light incident on the light guide plate 1 toward the other plate surface 1b, and is, for example, a large number of fine recesses formed on one plate surface 1a. The term "diffusion" as used herein also includes a mode in which light spreads by being reflected by, for example, a spherical surface or the like.

Specifically, these diffuse reflection portions 5 are, for example, partially concave spherical objects formed in one plate surface 1a of the light guide plate 1, and in this embodiment, as shown in FIG. 3, they are on square grid points. It is arranged regularly. The shape and arrangement of the diffuse reflection unit 5 are not limited to this, and may be changed to various modes.

As shown in FIG. 2, the LED 2 is, for example, a surface mount type, and a lineup of emission colors includes a plurality of colors such as white, red, and blue, but here, a white one is used. There is.

The substrate 3 is a printed wiring board on which the LED 2 is mounted, and is provided corresponding to each of the four sides of the light guide plate 1 as shown in FIG. Each substrate 3 has a long shape extending along the side surface 1c of the light guide plate 1, and here, a plurality of LEDs 2 are arranged in a row at a predetermined pitch, more specifically at an equal pitch p. .. In FIG. 4, a part of the internal structure of the frame body 4 is omitted in order to facilitate understanding of the substrate 3 and the LED 2.

As shown in FIGS. 1 and 2, the frame body 4 has a rectangular frame shape composed of four side members 41, and each side member 41 extends from end to end along the longitudinal direction and is guided. A step portion 4a on which the light plate 1 is placed and supports the peripheral edge portion of the light guide plate 1 is provided. As a result, the peripheral edge of the light guide plate 1 is masked (covered) by the frame body 4. Further, the step portion 4a also holds the substrate 3, and the light emitting surface of the LED 2 mounted on the substrate 3 is configured to face the side surface 1c of the light guide plate 1. With such a configuration, the light emitted from the LED 2 is introduced into the inside of the light guide plate 1 from the side surfaces 1c on all four sides.

In the light irradiation device 100 having such a configuration, the light emitted from the LED 2 is incident from the side surface 1c of the light guide plate 1 and travels inside while being repeatedly totally reflected between the opposing plate surfaces of the light guide plate 1. .. Then, most of the light hits the diffuse reflection unit 5 during the process, is diffusely reflected there, and is emitted to the outside from the other plate surface 1b of the light guide plate 1. More specifically, as described above, since the peripheral edge of the light guide plate 1 is covered with the frame body 4, light is emitted from the inside of the frame body 4 on the other plate surface 1b of the light guide plate 1. .. As a result, the other plate surface 1b becomes a light emitting surface.

In FIG. 2, reference numeral 6 is a transparent cover plate 6 that covers one plate surface 1a of the light guide plate 1. Reference numeral 7 is a viscoelastic heat conductor 7 that is interposed between the back surface of the wiring substrate 3 and the frame body 4 and is in close contact with both of them to conduct heat of the LED 2 to the frame body 4 and dissipate heat. Further, reference numeral 8 in the figure is a spacer 8 interposed between the surface of the wiring board 3 and the side surface 1c of the light guide plate 1 to keep the distance between them constant.

In the present embodiment, as shown in FIG. 2, the spacer 8 is urged toward the inside (light emitting direction of the LED 2) by an elastic body 9 (coil spring or leaf spring) provided on the outside thereof. By doing so, the front contact surface of the spacer 8 is brought into close contact with the side surface 1c of the light guide plate 1.

On the other hand, the substrate 3 is urged toward the inside (the light emitting direction of the LED 2) by the heat conductor 7, so that the substrate 3 is brought into close contact with the back side contact surface of the spacer 8.

With this structure, the spacer 8 is closely interposed between the surface of the substrate 3 and the side surface 1c of the light guide plate 1, and the distance between them is kept constant.

Next, the inspection system 200 using the light irradiation device 100 having such a configuration will be briefly described. As shown in FIGS. 1 and 2, the inspection system 200 includes a camera C in addition to the light irradiation device 100. Then, the other plate surface 1b of the light guide plate 1 is arranged so as to face the work W, and the work W is illuminated by the diffused light emitted from the other plate surface 1b, while being illuminated in this way. The work W is imaged by the camera C from the opposite side of the light guide plate 1, that is, from one plate surface 1a side of the light guide plate 1, and the captured image is used for inspection.

Therefore, as shown in FIGS. 5 and 6, the substrate 3 of the present embodiment is provided with a light source arrangement region S1 extending in the longitudinal direction and a light source non-arrangement region S2 outside the light source arrangement region S1 in the longitudinal direction. The length L2 along the longitudinal direction of the light source non-arrangement region S2 is set to be equal to or greater than the pitch p of the LED2. The pitch p referred to here is the distance between the corresponding portions of the LEDs 2 adjacent to each other along the longitudinal direction, for example, the distance between the corresponding sides and the distance between the centers (separation distance).

More specifically, as shown in FIG. 6, the light source arrangement area S1 is an area facing the side surface 1c of the light guide plate 1 and the LEDs 2 are arranged at a predetermined pitch p, in other words, on the substrate 3. All of the mounted LEDs 2 are arranged in the light source arrangement area S1.
As shown in FIG. 5, the light source arrangement region S1 here is set from one of the LEDs 2 located at both ends to the other on the surface of the substrate 3, and the length L1 along the longitudinal direction thereof is set. L1 = z × n + d × (n−), where z is the dimension along the longitudinal direction of the LED 2, d is the distance along the longitudinal direction of the adjacent LEDs 2, and n is the number of LEDs 2 mounted on the substrate 3. It is represented by 1). The interval d is the length obtained by subtracting the dimension z of the LED 2 from the pitch p.

On the other hand, the light source non-arrangement region S2 is an region facing the side surface 1c of the light guide plate 1 and in which the LED 2 as a light source is not arranged.
As shown in FIG. 5, the light source non-arrangement region S2 here is set on both one outer side and the other outer side along the longitudinal direction from the light source arrangement region S1. As shown in FIGS. 5 and 6, each of these light source non-arranged regions S2 is the entire region on the surface of the substrate 3 outside the longitudinal direction of the LEDs 2 located at both ends, and has a length L2 along the longitudinal direction. However, it is equal to or higher than the pitch p described above. In the present embodiment, the length L2 along the longitudinal direction of each light source non-arrangement region S2 is longer than the pitch p, and the entire surface of each light source non-arrangement region S2 faces the side surface 1c of the light guide plate 1. It is as a dimension. As a result, the substrate 3 of the present embodiment has a length substantially equal to or slightly shorter than the length along the longitudinal direction of the side surface 1c of the light guide plate 1.

Here, in order to improve the amount of light emitted from the main light irradiation device 100, at first glance, as shown in FIG. 7, it seems better to arrange the LED 2'also in the light source non-arrangement region S2. Is done.

However, although it depends on the distance from the LED 2'to the light guide plate 1, a part of the light emitted from the LED 2'arranged in the light source non-arranged region S2 is a part of the light emitted from the light guide plate 1 as shown in FIG. It spreads outward from the side surface 1c of the light guide plate 1 and does not enter the inside of the light guide plate 1. For this reason, despite the increase in the number of parts, the improvement in the amount of light is small, and the desired cost-effectiveness cannot be obtained.

On the other hand, if the LED 2 is not provided in the light source non-arrangement region S2, it is easy to think that the substrate 3 is unnecessarily long and merely causes an increase in material cost. It can be said that the idea is a fixed concept in this technical field.

However, in the conventional configuration in which the light source non-arrangement region S2 is not provided, as shown in FIG. 8, the light incident on the light guide plate 1 and reaching the corner portion 1x of the light guide plate 1 is the corner portion 1x. Leaks to the outside of the light guide plate 1 and causes a decrease in light utilization efficiency and a decrease in uniformity of irradiation light due to darkening of the four corners of the light guide plate 1.

Therefore, in the present embodiment, while providing the light source non-arrangement region S2 as described above, the light leaking from at least the corner portion 1x of the light guide plate 1 is transmitted to the light source non-arrangement region S2 on the side surface 1c of the light guide plate 1. It has a function as a reflecting surface that reflects toward the corner portion 1x and is incident on the light guide plate 1 again.

More specifically, the light source non-arrangement region S2 faces the side surface 1c of the substrate 3 as described above, and is arranged so that light passes between them without being blocked. The light source non-arranged region S2 has a higher reflectance than the light source arranged region S1, specifically, the reflectance is 50% or more, and in the present embodiment, it is 80% or more.

Here, the reflectance of the present embodiment is the wavelength of the light emitted from the LED 2 as a light source, in other words, the reflectance with respect to the wavelength of the irradiation light of the main light irradiation device 100, and specifically, it is incident on a certain region. It is the ratio of the total energy of the reflected light reflected in the same region to the total energy of the incident light. As described above, the white LED is used as the light source in this embodiment, and the reflectance of this embodiment is the reflectance with respect to the wavelength of white light.

Further, in the present embodiment, the reflectance of the light source arrangement region S1 and the reflectance of the light source non-arrangement region S2 are the average values of the reflectances in the entire region, and the reflectance of the light source arrangement region S1 is the reflection of the LED 2. It is the average value of the reflectance including the rate.

In the present embodiment, as shown in FIG. 5, a white solder resist layer R (shown by double diagonal lines in the figure) is formed at least in the light source non-arranged region S2 of the substrate 3, and here the light source is not arranged. A white solder resist layer R is formed not only in the region S2 but also in the light source arrangement region S1.

The white solder resist layer R is an insulating film that covers the surface of the substrate 3 with white resist ink, and has a reflectance of, for example, 85 or more and 90% or less. Specifically, the white solder resist layer R is made of, for example, silicon, titanium oxide, or the like, and may be, for example, a pure white one, a bluish white one, or a milky white one.

<Effect>
According to the light irradiation device 100 configured in this way, the length of the light source non-arranged region S2 along the longitudinal direction is equal to or greater than the pitch p of the LED2, and the light source non-arranged region S2 functions as a reflecting surface. Therefore, the light incident on the inside of the light guide plate 1 and leaking from the corner portion 1x can be incident on the inside of the light guide plate 1 again.
As a result, light leakage from the corner portion 1x of the light guide plate 1 can be reduced, light utilization efficiency can be improved, and the amount and uniformity of the irradiation light can be improved more than before.

Further, in the substrate 3 of the present embodiment, since the white solder resist layer R is formed not only in the light source non-arrangement region S2 but also in the light source arrangement region S1, for example, a conventional substrate on which a white solder resist layer is formed can be used. It can be easily manufactured by extending the length so that the light source non-arrangement region S2 is formed. This makes it possible to manufacture the light irradiation device 100 without increasing the number of parts and increasing the cost.

<Other Embodiments>
The invention of the present application is not limited to the above-described embodiment.

For example, in the above embodiment, the white solder resist layer R is formed on the surface of the substrate 3, but when the substrate 3 is a glass epoxy substrate on which, for example, a green solder resist layer is formed, solder is soldered to the light source non-arrangement region S2. A leveler may be provided. When the solder leveler is used in this way, the reflectance of the light source arrangement region S1 is 60 to 70%, which is higher than the reflectance of the light source arrangement region S1. In the configuration in which the white solder resist layer R is formed on the surface of the substrate 3 as in the above embodiment, a solder leveler may be provided in the light source non-arrangement region S2.

Further, in the above-described embodiment, the length dimension of the substrate 3 is substantially equal to or slightly shorter than the length along the longitudinal direction of the side surface 1c of the light guide plate 1, but as shown in FIG. 9, the side surface 1c of the light guide plate 1 It may be longer than the length along the longitudinal direction of.
In such a configuration, since the substrates 3 adjacent to each other are arranged without gaps or with almost no gaps, the material cost is higher than that of the above embodiment, but the light guide plate 1 is formed from the corner 1x. Light leakage can be further suppressed.

Further, the LEDs 2 do not have to be arranged at equal intervals, and for example, the LEDs 2 may be arranged closer to the outside than the central portion, or may be arranged in the opposite relationship. In short, the LEDs 2 may be regularly arranged along the longitudinal direction of the substrate 3. In this case, the light source non-arrangement region S2 is a region outside the light source arrangement region S1 in the longitudinal direction as in the above embodiment, and has a length capable of arranging the LED 2 when the arrangement rules of the LED 2 are obeyed. Moreover, it is an area where the LED 2 is not arranged.

In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

100 ... Light irradiation device 1 ... Light guide plate 1a ... One plate surface 1b ... The other plate surface 1c ... Side surface 1x ... Corner 2 ... LED
3 ・ ・ ・ Substrate 4 ・ ・ ・ Frame body S1 ・ ・ ・ Light source arrangement area S2 ・ ・ ・ Light source non-arrangement area

Claims (7)

A flat plate rectangular light guide plate, a substrate facing each side surface of the light guide plate, a plurality of light sources arranged on the substrate at a predetermined pitch, the light source and the substrate, and a peripheral portion of the light guide plate are accommodated. Equipped with a supporting frame
Light from the light source enters the inside of the light guide plate from the side surface, is reflected by one plate surface of the light guide plate, and is emitted to the outside from the other plate surface of the light guide plate to be a predetermined object. It is configured so that an object can be irradiated and the object can be observed from one plate surface side of the light guide plate through the light guide plate.
The substrate is provided with a light source arrangement region extending in the longitudinal direction and a light source non-arrangement region outside the light source arrangement region in the longitudinal direction.
A light irradiation device characterized in that the length of the light source non-arranged region along the longitudinal direction is equal to or greater than the predetermined pitch. The light irradiation device according to claim 1, wherein the reflectance of the light source non-arranged region is higher than the reflectance of the light source arranged region. The light irradiation device according to claim 1 or 2, wherein the reflectance of the light source non-arranged region is 50% or more. The light irradiation device according to any one of claims 1 to 3, wherein a white solder resist layer is formed at least in the light source non-arranged region on the substrate. The light irradiation device according to claim 4, wherein a white solder resist layer is formed in the light source arrangement region and the light source non-arrangement region in the substrate. The light irradiation device according to any one of claims 1 to 5, wherein a solder leveler is provided in the light source non-arrangement region of the substrate. The light irradiation device according to any one of claims 1 to 6, wherein the light source non-arrangement region faces the side surface of the light guide plate and passes between them without being blocked by light.

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