JP3900781B2 - Light irradiation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light irradiation apparatus that performs light treatment by guiding light emitted from a discharge lamp with a light guide to irradiate an object to be irradiated (work) disposed on the surface to be irradiated, and further to a narrow area. The present invention relates to a light irradiation apparatus suitable for performing ultraviolet treatment by irradiating light including ultraviolet light.
[0002]
[Prior art]
The adhesive, paint, ink, resist, or the like applied to the workpiece is irradiated with light emitted from the light irradiation device to be cured or dried. Conversely, various processes such as melting or softening these are performed. In addition, in the case of bonding an optical disk pickup lens with an ultraviolet curable adhesive or bonding an electronic component to a substrate, it is necessary to irradiate light in a very small area. It is guided by a light guide that is configured to irradiate a minute area.
[0003]
FIG. 1 shows an example of the internal configuration of a light irradiation apparatus for irradiating a minute region. The mirror 20 is fixed to the holding member 30, and the discharge lamp 10 is also fixed to the holding member 30 in a state of being inserted through the through hole 21 of the mirror 20. The discharge lamp 10 is a short arc type discharge lamp such as a xenon lamp or an ultra-high pressure mercury lamp, for example, and a cathode 11 and an anode 12 are disposed opposite to each other in an arc tube. The mirror 20 has an elliptical cross-sectional shape, and the bright spot of the light emitting portion between the cathode 11 and the anode 12 of the discharge lamp 10 is located at the first focal point of the mirror 20. Usually, the bright spot of the light emitting part is near the tip of the cathode. The light guide F is disposed on the optical axis L of the mirror 20, and the incident end Fin of the light guide F is located at the second focal point of the mirror 20. Further, a shutter St is disposed between the incident end Fin of the light guide F and the discharge lamp 10, and when the shutter St is opened, the light condensed by the mirror 20 enters the incident end Fin of the light guide F. To do. Then, the light emitted from the light emitting end Fou of the light guide F is irradiated onto a workpiece that performs light irradiation processing, such as a lens component or a substrate coated with an ultraviolet curable adhesive, disposed in the light irradiation region on the irradiated surface. The
[0004]
In such a light irradiation apparatus, since the through-hole 21 is formed in the central portion of the mirror 20 as described above, no reflected light exists in this portion, and the light reflected by the mirror 20 is a dotted line in FIG. Only the light indicated by the oblique lines enters the incident end Fin of the light guide F. That is, a large amount of light having a large incident angle is incident on the incident end Fin, and light near 0 ° having a small incident angle is hardly incident.
[0005]
The light incident on the incident end Fin of the light guide F is repeatedly reflected in a state where the angle is maintained as a property of the optical fiber, is transmitted through the light guide F, and is emitted from the emission end Fou at the same angle as the incident angle. As described above, since a large amount of light with a large incident angle is incident on the light guide F, a large amount of light with a large emission angle indicated by the dotted line in FIG. Here, if the distance d between the light emitting end Fou of the light guide F and the irradiated surface on which the work is placed is short, the illuminance distribution on the irradiated surface can be reduced even if there is little light close to 0 ° with a small emission angle. Since the convergent diameter of the optical fiber of the guide F has a certain size, for example, φ5 mm or φ3.5 mm, the illuminance at the center is high and the peripheral portion becomes a lower mountain shape.
[0006]
However, when the distance d between the light emitting end Fou of the light guide F and the irradiated surface is increased, the illuminance of the irradiated area on the irradiated surface is lower in the central portion than in the peripheral portion, and a phenomenon called “hollow” occurs. . FIG. 2 shows the relationship between the distance d between the light emitting end Fou of the light guide F and the irradiated surface and the “void” when the convergent diameter of the optical fiber is 3.5 mm. When the distance d is 20 mm or more, FIG. The “missing” phenomenon becomes noticeable. In many cases, the distance d between the light emitting end Fou of the light guide F and the irradiated surface on which the work is disposed is set to 20 mm or more due to the size and shape of the work, the clearance relationship with the work loading / unloading mechanism, and the like. .
[0007]
In order to shorten the light processing time, it is necessary to process with high illuminance. However, if a small work such as a pickup lens for an optical disk is placed in the center of the irradiation area when the distance between the emitting end Fou and the irradiated surface on which the work is placed is long, the work is caused by a “hollow-out” phenomenon. The illuminance of the irradiated light is reduced and the processing time is increased. For this reason, the work is shifted from the center of the irradiation area and is arranged and irradiated on the periphery of the irradiation area where the illuminance is high. However, when different types of workpieces are optically processed, or when the distance d between the exit end Fou of the light guide F and the irradiated surface on which the workpiece is placed is changed, the illuminance distribution on the irradiated surface is measured each time. Thus, it is necessary to obtain a place where the illuminance is highest and to set the work appropriately so that the workpiece comes to that position. Moreover, since the area | region with high illumination intensity is a peripheral part of an irradiation area | region and the range is narrow, it is necessary to align a workpiece | work position with sufficient precision, and time and effort were required for setup change.
[0008]
[Problems to be solved by the invention]
In order to eliminate this “hollow-out” phenomenon, it is considered that the light emitted from the light guide exit end is focused on the irradiated surface by the projection optical system and irradiated to the workpiece placed on the irradiated surface. It is done. In this case, since the illuminance distribution at the exit end of the light guide is projected onto the irradiated surface by the projection optical system, light can be efficiently irradiated to the area that needs to be irradiated on the irradiated surface, and the illuminance distribution The “missing” phenomenon can be eliminated.
[0009]
Japanese Patent Application Laid-Open No. 64-75067 discloses that a lens unit in which a plurality of lenses are combined is used as the projection optical system. FIG. 3 shows an example of a lens unit LU composed of a first lens L1 and a second lens L2. The lens unit LU is attached to the light guide emitting end, and a light irradiation unit is configured. In FIG. 3, the light emitted from the emission end Fou of the light guide F has a certain spread according to the numerical aperture NA of the optical fiber forming the light guide F. For example, in the case of an optical fiber made of quartz glass, the numerical aperture NA = about 0.22, and the spread angle in air corresponds to about 12.7 °.
[0010]
Here, when the lenses L1 and L2 of the lens unit LU are brought close to the emission end Fou of the light guide F, the magnification projected onto the irradiated surface by the lens unit LU increases. That is, since the projected area on the irradiated surface is increased, the illuminance of the entire irradiated region is reduced. Therefore, in order to irradiate a narrow area with high illuminance, it is necessary to separate the lenses L1 and L2 of the lens unit LU from the emission end Fou of the light guide F by a predetermined distance. In order to effectively use the light emitted from the light emitting end Fou of the light guide F, most of the light spread at the above-mentioned spread angle of about 12.7 ° must be collected by the lens. As shown in FIG. 3, it is necessary to increase the lens diameter of the lens unit LU. For this reason, the diameter of the lens unit including the holder H that holds the lens is considerably larger than the diameter of the light guide F, and the shape of the light emitting portion is increased.
Even when the distance between the lens and the irradiated surface is increased, the distance from the exit end Fou of the light guide F to the lens needs to be increased. The shape of the part increases.
[0011]
In actual light irradiation processing, there are cases where a jig for fixing a work surrounds the periphery of the jig, or a portion that irradiates light is surrounded by other components mounted on the substrate. However, in any case, if the shape of the light emitting part is large, it is not possible to irradiate the light emitting part sufficiently close to the part that irradiates the light of the workpiece, and the desired irradiance cannot be obtained. There is a bug.
[0012]
Therefore, the present invention does not increase the diameter of the light emitting portion, allows the light emitting portion to be close to the workpiece and irradiates light with high irradiance, and the light emitting portion and the workpiece are separated from each other. Even so, an object of the present invention is to provide a light irradiating apparatus capable of irradiating light efficiently without causing “spotting” of the light irradiated on the irradiated surface.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, the invention of claim 1 condenses the light emitted from the discharge lamp by the mirror, and the collected light enters the incident end of the light guide arranged on the optical axis of the mirror. In the light irradiation apparatus for condensing the light emitted from the emission end of the light guide onto the irradiated surface by the projection optical system and irradiating the irradiated object arranged on the irradiated surface, the projection optical system has both ends A rod lens having a spherical surface with the same radius of curvature and having an incident end close to the light guide exit end at an interval of 1 mm or less, and an outer diameter substantially equal to the convergence diameter of the light guide , The rod lens is composed of a plano-convex lens or a bi-convex lens whose outer diameter is arranged close to the exit end, which is substantially equal to the convergence diameter of the light guide , and the rod lens does not allow the light incident on the rod lens to hit the outer peripheral surface of the rod lens. Rodley Nsin θ = n′sin θ ′ (the refractive index of the rod lens material is n ′, the refractive index of air is n, and the spread angle of light in air is θ). The length is calculated from the light spread angle θ ′ in the rod lens and the diameter of the rod lens. The rod lens and plano-convex or biconvex lens are held by a cylindrical holder, and the holder covers the light guide emission end. It is joined to the tubular joint.
The projection optical system according to a second aspect of the present invention has a projection optical system, the incident end of which is arranged close to the light guide emission end at an interval of 1 mm or less, and both ends having an outer diameter substantially equal to the convergence diameter of the light guide. It consists of a spherical rod lens, the radius of curvature of the spherical surface of the exit end of the rod lens is smaller than the radius of curvature of the spherical surface of the entrance end, and the light incident on the rod lens does not hit the outer peripheral surface of the rod lens. In the rod lens obtained based on n sin θ = n ′ sin θ ′ (the refractive index of the rod lens material is n ′, the refractive index of air is n, and the spread angle of light in the air is θ). The length is calculated from the light spread angle θ ′ and the diameter of the rod lens. The rod lens is held by a cylindrical holder, and the holder is bonded to a cylindrical joint that covers the light guide emission end. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 4 is a cross-sectional view of an embodiment of the light emitting portion of the invention of claim 1. That is, the light source part of the light irradiation device of the present invention is as shown in FIG. 1, and the tip of the light guide F in FIG. 1 has the structure shown in FIG.
In FIG. 4, the light guide F is formed by bundling a large number of optical fibers made of quartz glass so that the positions of the individual optical fibers at the incident end Fin and the output end Fou are random. The side surface of the light emitting end Fou of the light guide F is covered with a joint portion FJ that is a cylindrical hardware, and a cylindrical holder H is joined to the joint portion FJ. A quartz glass rod lens 40 and a plano-convex lens 50 serving as a projection optical system are held in the holder H. Here, the outer diameters of the rod lens 40 and the plano-convex lens 50 are substantially equal to or slightly larger than the convergence diameter of the optical fiber. A specific example of the convergent diameter of the optical fiber is, for example, φ3.5 mm, and the outer diameter of the joint portion FJ is φ9 mm. The outer diameters of the rod lens 40 and the plano-convex lens 50 are the same as or slightly larger than φ3.5 mm. Accordingly, since the projection optical system can be provided without making the outer diameter of the holder H larger than the outer diameter of the joint portion FJ, the outer diameter of the light emitting portion does not increase.
[0015]
Both ends of the rod lens 40 are spherical surfaces, one end is an incident surface on which light from the light guide F is incident, and the other end is an output surface from which incident light is emitted. The entrance surface of the rod lens 40 is provided close to the exit end Fou of the light guide F. In other words, the incident surface of the rod lens 40 is in contact with the emission end Fou of the light guide F or is held at a short interval of 1 mm or less. The curvature radius R1 of the entrance surface of the rod lens 40 is equal to the curvature radius R2 of the exit surface. The radius of curvature of the plano-convex lens 50 provided on the exit surface side of the rod lens 40 is R3. The radius of curvature R3, the radius of curvature R1 (= R2) of the rod lens 40 and the optical axis direction of the rod lens 40 are shown. The length is designed according to the distance d to the irradiated surface that collects the light emitted from the plano-convex lens 50.
The plano-convex lens 50 may be a biconvex lens.
[0016]
FIG. 5 shows an embodiment of the light emitting portion according to the invention of claim 2. In the holder H, only the rod lens 40 whose outer diameter is substantially equal to or slightly larger than the convergence diameter of the optical fiber is held. Both ends of the rod lens 40 are spherical as in the case of the first embodiment, but by making the radius of curvature R2 of the exit surface smaller than the radius of curvature R1 of the entrance surface, a convex lens is formed on the exit side of the rod lens 40. It is not necessary to provide The curvature radii R1 and R2 and the length of the rod lens 40 in the optical axis direction are designed according to the distance d to the irradiated surface that collects the light emitted from the rod lens 40.
[0017]
When the discharge lamp 10 shown in FIG. 1 is turned on and the shutter St is opened, the light collected by the mirror 20 enters the incident end Fin of the light guide F and exits from the exit end Fou of the light guide F. However, in the case of the invention of claim 1, as shown in FIG. 6, the light emitted from the optical fiber at the substantially central portion of the emission end Fou of the light guide F has a maximum emission angle of 12.7 ° (the NA of the fiber). Is equivalent to about 0.22), the light is refracted at the entrance surface of the rod lens 40 and reaches the exit surface of the rod lens 40 while spreading at an angle of about 8.6 °. Then, the light exits from the exit surface of the rod lens 40 as light substantially parallel to the optical axis.
On the other hand, the light emitted from the optical fiber at the periphery of the light emitting end Fou of the light guide F is refracted in the optical axis direction of the light guide F and is incident on the rod lens 40 because the incident surface of the rod lens 40 is spherical. Thereafter, the light reaches the exit surface of the rod lens 40 while spreading at an angle of about 8.6 °. The light exits from the center of the light guide F on the exit surface of the rod lens 40 and exits from the exit surface of the rod lens 40 at an angle close to 12.7 ° with respect to the optical axis.
The spread angle θ ′ (about 8.6 °) in the rod lens 40 is such that the refractive index n ′ (= 1.47) of quartz glass, which is the material of the rod lens 40, and the refractive index n (= 1) of air. ) And the spread angle θ in air (12.7 °) can be obtained based on Snell's law (nsinθ = n′sinθ ′).
[0018]
In order to use the light most efficiently , the light incident on the rod lens 40 is made to spread over the exit surface of the rod lens 40 without hitting the outer peripheral surface of the rod lens 40 as shown in FIG . Therefore, the length of the rod lens 40 is slightly shorter than about 12 mm or 12 mm because the material is quartz glass and the diameter is φ3.5 mm, and the spread angle is about 8.6 ° .
[0019]
The light emitted from the exit surface of the rod lens 40 enters the plano-convex lens 50, and the light exited from the plano-convex lens 50 is refracted based on the radius of curvature R3 of the plano-convex lens 50, and enters the light irradiation surface at the set position. Condensate. Here, the distance d from the plano-convex lens 50 to the irradiated surface corresponds to the focal length of the plano-convex lens 50. That is, the rod lens 40 and the plano-convex lens 50 function as a projection lens that projects the illuminance distribution of the emission end Fou of the light guide F onto the irradiated surface. In addition, the illuminance distribution at the emission end Fou of the light guide F is made uniform by the effect of random arrangement of optical fibers. Therefore, due to the action of the rod lens 40, even if the distance d from the emitting part to the irradiated surface is increased, the “illuminance” does not occur in the illuminance distribution of the irradiated area on the irradiated surface.
[0020]
8 shows the above-described embodiment in which the projection optical system including the rod lens 40 and the plano-convex lens 50 is provided at the emission end Fou of the light guide F, and FIG. 1 in which the projection optical system is not provided at the emission end Fou of the light guide F. The irradiance distribution curve of the prior art example shown is shown. Irradiance distribution curves were obtained when the distance d from the emitting end Fou of the plano-convex lens 50 or the light guide F to the irradiated surface was 15 mm and 20 mm. The rod lens 40 and the plano-convex lens 50 have the distance d = 15 mm. Designed as. The convergence diameter of the optical fiber is φ3.5 mm.
[0021]
As can be seen from FIG. 8, in this example, no “collapse” phenomenon was observed in both cases of d = 15 mm and d = 20 mm. In this example, since the light is condensed on the irradiated surface with d = 15 mm, the illuminance at the center of the irradiation region is much larger than that of the conventional example, and a sharp distribution curve is obtained. On the other hand, in the conventional example, not only the illuminance at the central portion of the irradiation area is lower than in the present embodiment, but also a “collapse” phenomenon is observed when d = 20 mm.
[0022]
FIG. 7 shows an example of the optical path diagram of the invention of claim 2 in which the plano-convex lens 50 is not used, but the optical path diagram of the invention of claim 1 is shown until the light incident on the rod lens 40 reaches the exit surface. It is the same as FIG. 6 shown. However, since the radius of curvature R2 of the exit surface of the rod lens 40 is smaller than the radius of curvature R1 of the entrance surface, the light is refracted more than when incident and exits from the rod lens 40 and is collected on the light irradiation surface at the set position. Shine. That is, since the rod lens 40 functions as a projection lens that projects the illuminance distribution of the emission end Fou of the light guide F onto the irradiated surface, it has the same effect as using the plano-convex lens 50, and irradiation on the irradiated surface is performed. There is no “void” in the illuminance distribution of the area. Since the plano-convex lens 50 is not used, the number of parts can be reduced, and light loss due to reflection and absorption is reduced, resulting in an increase in illuminance.
[0023]
【The invention's effect】
As described above, the present invention condenses the light emitted from the light guide on the irradiated surface by the rod lens or the projection optical system composed of the rod lens and the planoconvex or biconvex lens. Even when the distance is large, the “distribution” phenomenon does not occur in the illuminance distribution, and the irradiance at the center of the irradiation area can be increased.
Conventionally, the ratio of the air layer between the light guide and the lens is large, and the lens diameter is large correspondingly. The air layer is replaced with a rod lens having a large refractive index. As a result, the diameters of the rod lens and the plano-convex or biconvex lens can be made substantially equal to the diameter of the light guide. Therefore, the diameter of the light emitting portion does not increase despite the provision of the projection optical system at the light guide emitting end. For this reason, even when the clearance between the workpiece, which is an object to be irradiated, and its carry-in mechanism, etc. is small, the light emitting section can be brought close to the workpiece. Further, even if the distance from the emitting portion to the workpiece is increased, it is possible to irradiate light without “hollow-out”. Therefore, it is possible to easily adjust the irradiation conditions regardless of the distance from the emitting end to the irradiated surface, and even if the material and type of the workpiece change, it is possible to respond freely to the irradiation conditions. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a light irradiation device.
FIG. 2 is an explanatory diagram of “blank” in the illuminance distribution.
FIG. 3 is an explanatory diagram of a conventional example of a light emitting unit.
FIG. 4 is a cross-sectional view of a light emitting portion according to the first aspect of the present invention.
5 is a cross-sectional view of a light emitting portion according to the invention of claim 2. FIG.
6 is an optical path diagram of the invention of claim 1; FIG.
7 is an optical path diagram of the invention of claim 2. FIG.
FIG. 8 is an irradiance distribution curve diagram.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Discharge lamp 11 Cathode 12 Anode 20 Mirror 30 Holding member 40 Rod lens 50 Plano-convex lens F Light guide Fin Light guide entrance end Fou Light guide exit end FJ Joint H Holder St Shutter

Claims (2)

Light emitted from the discharge lamp is collected by a mirror, and the collected light is incident on an incident end of a light guide disposed on the optical axis of the mirror, and the above-mentioned light emitted from the exit end of the light guide is projection optics. In the light irradiation device that focuses on the irradiated surface by the system and irradiates the irradiated object arranged on the irradiated surface,
The projection optical system has spherical surfaces having the same radius of curvature at both ends, the incident end is disposed close to the light emitting end of the light guide at an interval of 1 mm or less , and the outer diameter is the convergence diameter of the light guide. A substantially equal rod lens, and a plano-convex or biconvex lens having an outer diameter arranged close to the exit end of the rod lens is substantially equal to the convergence diameter of the light guide ,
The rod lens has nsin θ = n′sin θ ′ (the refractive index of the material of the rod lens is n ′ so that the light incident on the rod lens spreads on the exit surface of the rod lens without hitting the outer peripheral surface of the rod lens. , The refractive index of air is n, and the light spread angle θ ′ in the air is calculated based on the light spread angle θ ′ in the rod lens and the diameter of the rod lens.
The rod lens and the plano-convex lens or the biconvex lens are held by a cylindrical holder, and the holder is bonded to a cylindrical bonding portion that covers an emission end of the light guide . Light emitted from the discharge lamp is collected by a mirror, and the collected light is incident on an incident end of a light guide disposed on the optical axis of the mirror, and the above-mentioned light emitted from the exit end of the light guide is projection optics. In the light irradiation device that focuses on the irradiated surface by the system and irradiates the irradiated object arranged on the irradiated surface,
The projection optical system is composed of a spherical rod lens whose both ends are arranged close to the exit end of the light guide at an interval of 1 mm or less and whose outer diameter is substantially equal to the convergence diameter of the light guide , The radius of curvature of the spherical surface of the exit end of the rod lens is smaller than the radius of curvature of the spherical surface of the entrance end so that light incident on the rod lens spreads on the exit surface of the rod lens without hitting the outer peripheral surface of the rod lens. , N sin θ = n ′ sin θ ′ (the refractive index of the rod lens material is n ′, the refractive index of air is n, the light spread angle in the air is θ), and the light spread angle in the rod lens is the length calculated from θ ′ and the diameter of the rod lens,
The rod lens is held by a cylindrical holder, and the holder is joined to a tubular joint that covers the light guide output end .

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