Light projection device

Abstract

This light projection device includes: a light source; a light-transmitting plate disposed forward in the light emission direction of the light source; a porous plate placed and held above the light-transmitting plate and forming a light emitting surface for radiating light transmitted through the light-transmitting plate; a housing for integrally holding the light source, the light-transmitting plate, and the porous plate; and intake holes provided on an outer surface of the housing and communicating with side surfaces of the porous plate.

Description

Light irradiation device

[0001] The present invention relates to a light irradiation device.

[0002] As a method for inspecting the surface of a workpiece, a method is conventionally known in which a workpiece is placed on the light emitting surface of a surface-emitting light irradiation device, inspection light, which is backlight light, is irradiated onto the workpiece, and the transmitted light is inspected by visual observation or photographing (for example, Patent Document 1, etc.).

[0003] Japanese Patent Application Laid-Open No. 2003-139712

[0004] By the way, in the inspection method using the above-described backlight type light irradiation device, for example, there is a demand to inspect a film-shaped workpiece or a thin plate-shaped workpiece while holding it on the light emitting surface without warping or bending.

[0005] In order to meet such a demand, the inventor has devised a light irradiation device that also has a function as an adsorption surface for adsorbing a workpiece on the light emitting surface that emits inspection light, as shown in FIG. 8. The light irradiation device of FIG. 8 is configured such that an opening of a housing that houses a light source mounting substrate that emits inspection light is closed with a porous plate. The porous plate diffuses and transmits light, and its plate surface functions as a light emitting surface that emits light emitted from the light source mounting substrate. Further, the porous plate can transmit gas through innumerable pores, and by connecting a suction pump to an intake hole provided in the side wall of the housing and driving it, outside air is sucked into the housing through the porous plate, and the surface (light emitting surface) of the porous plate also functions as an adsorption surface. By adsorbing and holding the workpiece using such an adsorption surface, it becomes possible to suppress warping and bending of film-shaped or thin plate-shaped workpieces and perform inspection.

[0006] However, as the inventor repeatedly studied, in the configuration as shown in FIG. 8, when the suction pump is driven, the stress applied in the plate thickness direction of the porous plate due to the differential pressure between the atmosphere side and the inside of the housing increases, and the porous plate may bend so as to warp toward the inside of the housing, and there is a risk that the luminance uniformity of the light emitting surface may decrease.

[0007] The present invention has been made in view of these problems, and its main objective is to provide a light irradiation device with an adsorption function that can suppress the decrease in brightness uniformity caused by the bending of the light-emitting surface.

[0008] In other words, the light irradiation device according to the present invention is characterized by comprising: a light source; a light-transmitting plate positioned in front of the light emission direction of the light source; a porous plate placed on the light-transmitting plate and forming a light-emitting surface that emits light transmitted through the light-transmitting plate; a housing that integrally holds the light source, the light-transmitting plate, and the porous plate; and an intake hole provided on the outer surface of the housing that communicates with the side surface of the porous plate.

[0009] With such a design, by connecting, for example, a suction pump to the intake holes communicating with the side surface of the porous plate and driving it, the numerous pores formed in the porous plate can be made to create negative pressure, allowing air to be drawn in through the light-emitting surface, and the light-emitting surface can also function as an adsorption surface for adsorbing workpieces. Moreover, since the bottom surface of the porous plate is covered with a light-transmitting plate and the intake holes communicate with the side surface of the porous plate, when the suction pump is driven, the stress on the porous plate in the thickness direction can be reduced by the differential pressure, suppressing deflection due to warping of the porous plate and suppressing a decrease in the uniformity of the brightness of the light-emitting surface. Furthermore, since the deflection of the porous plate can be suppressed, there is no need to give the porous plate itself excessive strength, so the thickness can be reduced, thereby increasing the radiance of the light-emitting surface and enabling miniaturization of the device. In this specification, "porous" means that pores with a diameter of 5 μm or more and 200 μm or less are formed with a porosity of 30% or more and 80% or less.

[0010] Preferably, a suction channel is formed along the circumferential side surface of the porous plate, and the intake hole is in communication with the suction channel. This allows for a larger exhaust area (area through which air passes) on the circumferential side surface of the porous plate, thereby reducing pressure loss. As a result, the workpiece can be held with a strong suction force on the light-emitting surface.

[0011] Preferably, the suction channel is formed around the entire circumference of the side surface of the porous plate. This maximizes the exhaust area on the side surface of the porous plate, minimizing pressure loss. As a result, the workpiece can be held with stronger adsorption force on the light-emitting surface. Furthermore, since the pressure applied to the side surface of the porous plate can be made substantially uniform around the entire circumference, the air taken in from the light-emitting surface flows out substantially uniformly in the entire circumference along the plate surface. Therefore, the adsorption force is applied uniformly in all areas of the light-emitting surface, making it easier to evenly adhere workpieces such as films to the light-emitting surface. In addition, it prevents localized reduction in radiance caused by blockage due to the absorption of a large amount of foreign matter such as dust from the atmosphere in only a part of the porous plate. Moreover, since air is drawn in from the entire circumference of the side surface of the porous plate, unevenness in airflow can be suppressed, and the reduction in radiance uniformity caused by uneven heat dissipation performance in each area where light sources are placed, resulting in some light sources degrading faster than others, can be suppressed.

[0012] It is preferable that the multiple intake holes are provided at approximately equal intervals along the outer circumferential surface of the housing. This allows the pressure applied to the side surface of the porous plate to be more uniform over its entire circumference.

[0013] A specific embodiment of the light irradiation device is one in which the light source is positioned opposite the side surface of the light-transmitting plate, and the light-transmitting plate guides the light introduced from the side to the porous plate. With such an embodiment, the device can be made thinner compared to one in which the light source is positioned opposite the surface of the light-transmitting plate. In addition, since the light source can be positioned near the side surface of the porous plate, which is a passage for the drawn-in air, the light source can be cooled efficiently.

[0014] Furthermore, the light irradiation device preferably has a housing space for housing the light source formed by the inner wall surface of the housing and the surface of the light-transmitting plate, and this housing space is fluidically isolated from the intake hole. In this way, since the housing space is fluidly isolated from the intake hole, the decrease in heat dissipation performance due to the elimination of air convection caused by the housing space becoming a vacuum can be suppressed.

[0015] According to the present invention configured in this manner, it becomes possible to provide a light irradiation device with an adsorption function that can suppress the decrease in brightness uniformity caused by the bending of the light-emitting surface.

[0016] A perspective view showing the configuration of a light irradiation device according to one embodiment of the present invention. A perspective view showing the internal configuration of the light irradiation device according to the same embodiment. A cross-sectional view showing the configuration of the light irradiation device according to the same embodiment. A plan view showing the internal configuration of the light irradiation device according to the same embodiment. A cross-sectional view showing the configuration of a light irradiation device according to another embodiment. A cross-sectional view showing the configuration of a light irradiation device according to another embodiment. A cross-sectional view showing the configuration of a light irradiation device according to another embodiment. A diagram showing an example of a light irradiation device devised by the inventors leading up to the present invention.

[0017] Hereinafter, a light irradiation device 100 according to one embodiment of the present invention will be described with reference to the drawings.

[0018] The light irradiation device 100 of this embodiment is a surface light emitting device for inspection that irradiates inspection light onto a film-like or thin plate-like workpiece from a planar light-emitting surface S. This light irradiation device 100 is configured such that the light-emitting surface S that emits inspection light also functions as a suction surface that attracts and holds the workpiece.

[0019] Specifically, as shown in Figure 1-3, the light irradiation device 100 comprises a light source mounting substrate 1 on which a light source 11 is mounted, a light-transmitting plate 2 positioned in front of the light emission direction of the light source mounting substrate 1, a porous plate 3 placed on the light-transmitting plate 2 and forming a light-emitting surface S that emits light transmitted through the light-transmitting plate 2, and a housing 4 that houses and integrally holds the light source mounting substrate 1, the light-transmitting plate 2, and the porous plate 3.

[0020] The light source mounting board 1 has a rectangular (square) shape in plan view, with multiple light sources 11 (specifically LEDs) mounted in a matrix. This light source mounting board 1 is fixedly attached to the bottom wall 41 of the housing 4.

[0021] The light-transmitting plate 2 is a light-transmitting plate with a roughly constant thickness and a rectangular (square) shape in plan view. This light-transmitting plate 2 is made of an airtight material that does not allow gas to pass through, and in this embodiment it is a glass plate or a plastic plate. The light-transmitting plate 2 is held in the housing 4 such that one of its surfaces (back) faces the mounting surface of the light source mounting substrate 1. The inspection light emitted from the light source mounting substrate 1 is introduced from one surface (back) of the light-transmitting plate 2 and emitted from the other surface (front). The surface of the light-transmitting plate 2 facing the mounting surface of the light source mounting substrate 1 and the inner wall surface of the housing 4 form a housing space R for housing the light source mounting substrate 1.

[0022] The porous plate 3 has numerous minute pores formed on its surface and inside, allowing gas to pass through and diffuse inspection light to transmit through it. The porous plate 3 has a pore diameter of 5 μm to 200 μm, a porosity of 30% to 80%, and a haze (cloudiness) of 65.0% to 99.9%, and in this embodiment, it is made of semilux porous material.

[0023] The porous plate 3 has a roughly constant thickness and is rectangular (square) in plan view. In this embodiment, the porous plate 3 has a thickness less than the thickness of the light-transmitting plate 2, and its area in plan view is smaller than the area of ​​the light-transmitting plate 2. In plan view, the porous plate 3 is placed in close contact with the upper surface 21 of the light-transmitting plate 2 such that its center of gravity coincides with the center of gravity of the light-transmitting plate 2, and the pores formed on the lower surface 32 of the porous plate 3 are blocked by the upper surface 21 of the light-transmitting plate 2.

[0024] The housing 4 is a hollow rectangular parallelepiped with a rectangular (square) shape in plan view, and comprises a bottom wall 41, rectangular tubular side walls 42, and a top wall 43 with an opening in the center. The light source mounting substrate 1 is attached to the bottom wall 41, and the porous plate 3 is attached to the top wall 43 by sealing the opening airtight with adhesive or the like. The light-transmitting plate 2 is attached so as to be in contact with the top wall 43 and side walls 42 of the housing 4, by sealing the opening airtight with adhesive. In this way, the light-transmitting plate 2 is held between the porous plate 3 and the light source mounting substrate 1. One surface of the porous plate 3 is exposed from the top wall 43 of the housing 4, and this surface functions as a light-emitting surface S that emits inspection light and a suction surface that attracts the workpiece.

[0025] The housing 4 of this embodiment is composed of a plurality of divisible members, specifically a lower housing member 4a that holds the light source mounting substrate 1, and an upper housing member 4b that holds the porous plate 3 and the light-transmitting plate 2.

[0026] The lower housing member 4a forms the bottom wall 41 of the housing 4 and the lower region of the side wall 42 of the housing 4. The upper housing member 4b forms the upper wall 43 of the housing 4 and the upper region of the side wall 42 of the housing 4. The annular upper end surface of the side wall 42 of the lower housing member 4a and the annular lower end surface of the side wall 42 of the upper housing member 4b are brought facing each other and fixed with a fixing mechanism to form a hollow rectangular parallelepiped housing 4.

[0027] The aforementioned light-transmitting plate 2 is fixedly attached to the upper housing member 4b by adhesive, with its side circumferential surface being bonded to the inner wall surface of the side wall 42 of the upper housing member 4b, and the outer peripheral edge of its upper surface 21 being bonded to the wall surface of the upper wall 43 of the upper housing member 4b.

[0028] The fixing mechanism for securing the lower housing member 4a and the upper housing member 4b may, for example, consist of a pair of magnets provided on the opposing end faces of the side walls 42 of the lower housing member 4a and the upper housing member 4b, but is not limited to this. The fixing mechanism may also be a mechanism that utilizes screws, for example. The housing 4 may also be equipped with a positioning mechanism for positioning the lower housing member 4a and the upper housing member 4b. The positioning mechanism may, for example, consist of a recess and a protrusion that fit together and are provided on the opposing end faces of the side walls 42 of the lower housing member 4a and the upper housing member 4b.

[0029] It is preferable that the lower housing member 4a and the upper housing member 4b are configured to be detachable. With this configuration, for example, if the porous plate 3 becomes clogged with foreign matter such as dust in the atmosphere, the entire upper housing member 4b can be replaced.

[0030] The light irradiation device 100 is equipped with an intake hole 5 on the outer surface (specifically, the outer wall surface) of the housing 4, which communicates with the side circumferential surface 33 of the porous plate 3. By connecting a suction pump to this intake hole 5, for example, via an adapter or hose, and driving the suction pump, the pores formed in the porous plate 3 become negatively pressurized. As a result, as shown in Figure 3, air is drawn in through the upper surface 31 (light-emitting surface S) of the porous plate 3, and the light-emitting surface S also functions as an adsorption surface.

[0031] The light irradiation device 100 of this embodiment is equipped with a plurality of intake holes 5 provided along the outer circumferential surface of the housing 4. When viewing the light-emitting surface S of the porous plate 3 from above, one intake hole 5 is provided at the center of each side of the housing 4.

[0032] The housing 4 (specifically the upper wall 43 of the upper housing member 4b) forms a suction channel C that fluidly connects the intake hole 5 and the side circumferential surface 33 of the porous plate 3. This suction channel C is formed parallel to the light-emitting surface S and includes a circumferential channel C1 formed along the side circumferential surface 33 of the porous plate 3 when the light-emitting surface S of the porous plate 3 is viewed from above, and a connecting channel C2 that connects the circumferential channel C1 and the intake hole 5. The intake hole 5 and the suction channel C are spatially isolated from the aforementioned containment space R.

[0033] As shown in Figures 3 and 4, a portion of the channel wall surface of the circumferential channel C1 is composed of the side circumferential surface 33 of the porous plate 3. This circumferential channel C1 is formed along the edge of the porous plate 3 with equal width and height. The circumferential channel C1 is formed along at least one edge of the porous plate 3, and in this embodiment, it is formed around the entire circumference of the side circumferential surface 33 of the porous plate 3. In this embodiment, the entire circumference of the porous plate 3 is surrounded by a single annular circumferential channel C1, but the entire circumference of the porous plate 3 may also be surrounded by a plurality of linear circumferential channels C1.

[0034] The connecting channel C2 is formed to intersect the circumferential channel C1. In the light irradiation device 100 of this embodiment, multiple connecting channels C2 are formed corresponding to each of the multiple intake holes 5. That is, each connecting channel C2 is formed to intersect each side of the circumferential channel C1.

[0035] With the light irradiation device 100 of this embodiment configured in this way, by connecting, for example, a suction pump to the intake holes 5 that communicate with the side circumferential surface 33 of the porous plate 3 and driving it, the countless pores formed in the porous plate 3 can be made to negative pressure, allowing air to be drawn in through the light-emitting surface S, and the light-emitting surface S can also function as an adsorption surface for adsorbing workpieces. Moreover, since the lower surface 32 of the porous plate 3 is covered with a light-transmitting plate 2 made of an airtight material, and the intake holes 5 communicate with the side circumferential surface 33 of the porous plate 3, when the suction pump is driven, the stress applied to the porous plate 3 in the thickness direction can be reduced by differential pressure, the deflection due to warping and bending of the porous plate 3 can be suppressed, and the decrease in the uniformity of the brightness of the light-emitting surface S can be suppressed. Furthermore, since the deflection of the porous plate 3 can be suppressed, there is no need to give the porous plate 3 excessive strength, so the thickness can be reduced, thereby increasing the radiance of the light-emitting surface S and making the device smaller.

[0036] Since a suction channel C is formed along the entire circumference of the side surface 33 of the porous plate 3, and intake holes 5 are provided at approximately equal intervals along the outer surface of the housing 4, the exhaust area (area through which air passes) on the side surface 33 of the porous plate 3 can be maximized, and pressure loss can be minimized. As a result, the workpiece can be held with a stronger adsorption force on the light-emitting surface S. In addition, since the pressure applied to the side surface 33 of the porous plate 3 can be made approximately uniform around the entire circumference, the air taken in from the light-emitting surface S flows out approximately uniformly in the entire circumference along the plate surface. Therefore, the adsorption force is applied uniformly in all areas of the light-emitting surface S, making it easier to evenly adhere workpieces such as films to the light-emitting surface S. Furthermore, it is possible to prevent localized reduction in radiance caused by blockage due to the absorption of a large amount of foreign matter such as dust from the atmosphere in only a part of the porous plate 3. In addition, since air is drawn in from the entire circumference of the side surface 33 of the porous plate 3, unevenness in airflow can be suppressed, and a decrease in radiance uniformity caused by uneven heat dissipation performance in each region where the light source 11 is located, resulting in some light sources 11 degrading faster, can be suppressed.

[0037] Furthermore, since the containment space R is fluidly isolated from the intake port 5, the decrease in heat dissipation performance caused by the elimination of air convection due to the containment space R becoming a vacuum can be suppressed.

[0038] It should be noted that the present invention is not limited to the above-described embodiments. For example, in the above-described embodiments, the suction channel C was formed over the entire circumference of the side surface 33 of the porous plate 3, but this is not limited to that. The suction channel C may be formed in any way as long as it can communicate the intake hole 5 with the side surface 33 of the porous plate 3.

[0039] Furthermore, while the light irradiation device 100 of the above embodiment was equipped with a plurality of intake holes 5, it is not limited to this. The light irradiation device 100 of other embodiments may be equipped with only one intake hole 5. When the light irradiation device 100 is equipped with a plurality of intake holes 5, it is preferable, but not limited to this, that the plurality of intake holes 5 are provided at approximately equal intervals along the outer circumferential surface of the housing 4. For example, depending on the overall configuration of the device, the plurality of intake holes 5 may be provided at intervals that are not approximately equal.

[0040] Another embodiment of the light irradiation device 100, as shown in Figure 5, further includes a covering member 6 that covers and seals pores formed in the outer peripheral region of the light-emitting surface S in order to strengthen the suction force of the workpiece on the light-emitting surface S. This covering member 6 has an annular shape in plan view and covers and hides the outer peripheral region of the light-emitting surface S while exposing its inner region. Specifically, this covering member 6 may be a transparent film that transmits inspection light, or a reflective film that reflects inspection light.

[0041] Furthermore, while the light irradiation device 100 of the above embodiment had light emitted from the light source 11 introduced from the surface (back side) of the light-transmitting plate 2, it is not limited to this. In other embodiments of the light irradiation device 100, as shown in Figure 6, the light source mounting substrate 1 is arranged facing the side surface of the light-transmitting plate 2, and the light emitted from the light source 11 may be introduced from the side of the light-transmitting plate 2. In this case, the light-transmitting plate 2 may comprise a light-transmitting plate such as a glass plate, and a reflective member 7 such as a reflector such as a mirror or a reflective film attached to its surface (back side). The light-transmitting plate 2 may also have a reflective film such as a vapor-deposited film formed on the back surface of the light-transmitting plate. In addition, to guide light uniformly to the porous plate 3, the light-transmitting plate 2 may have dot processing on its back surface (bottom surface) or a dot pattern printed on it.

[0042] Furthermore, although the porous plate 3 in the above embodiment was made of a ceramic material, it is not limited to this. The porous plate 3 in other embodiments may be made of a plastic material. By making the porous plate 3 out of a plastic material, the thickness can be reduced compared to when it is made of a ceramic material, and the light-emitting surface S can be made brighter. On the other hand, if the thickness of the porous plate 3 is reduced, the bonding area between the side surface 33 of the porous plate 3 and the side surface of the upper housing member 4b will be reduced, and the bonding strength will not be maintained. For this reason, as shown in Figure 7, it is preferable to make the lower part of the outer surface 33 of the porous plate 3 protrude outward to form a flange portion 33a. In this way, the upper surface of the flange portion 33a can be used as a bonding surface with the upper housing member 4b, and the bonding area can be increased. This makes it possible to reduce the plate thickness while maintaining the bonding strength.

[0043] In addition, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit thereof.

[0044] According to the present invention, it is possible to provide a light irradiation device with an adsorption function that can suppress a decrease in luminance uniformity caused by bending of a light emitting surface.

[0045] 100... Light irradiation device 1... Light source mounting substrate 2... Translucent plate 3... Porous plate 4... Housing 5... Air intake hole S... Light emitting surface

Claims

1. A light irradiation device comprising: a light source; a light-transmitting plate positioned in front of the light emission direction of the light source; a porous plate placed on the light-transmitting plate and forming a light-emitting surface that emits light transmitted through the light-transmitting plate; a housing that integrally holds the light source, the light-transmitting plate, and the porous plate; and an air intake hole provided on the outer surface of the housing that communicates with the side surface of the porous plate.

2. The light irradiation device according to claim 1, wherein a suction channel is formed along the side surface of the porous plate, and the intake hole is in communication with the suction channel.

3. The light irradiation device according to claim 2, wherein the suction channel is formed around the entire circumference of the side surface of the porous plate.

4. The light irradiation device according to claim 3, wherein a plurality of the intake holes are provided at substantially equal intervals along the outer circumferential surface of the housing.

5. The light irradiation device according to claim 1, wherein the light source is positioned opposite the side surface of the light-transmitting plate, and the light-transmitting plate guides the light introduced from the side to the porous plate.

6. The light irradiation device according to claim 1, wherein a housing space for housing the light source is formed by the inner wall surface of the housing and the surface of the light-transmitting plate, and the housing space is fluidly isolated from the intake hole.

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