JP7531360B2 - Ultraviolet irradiation equipment - Google Patents

Description

The present invention relates to an ultraviolet irradiation device that irradiates ultraviolet light, and an ultraviolet flaw detection device that irradiates the surface of an object to be inspected with ultraviolet light to analyze the surface condition of the object, and more specifically to an ultraviolet irradiation device used to excite fluorescent materials in fluorescent magnetic particle inspection, fluorescent penetrant inspection, etc.

Magnetic particle testing and penetrant testing, which are types of non-destructive testing, are known as methods for inspecting the surface of steel and other test objects. In magnetic particle testing, magnetic powder or a magnetic powder solution containing magnetic powder is applied to the surface of the test object, and the test object is magnetized by applying a magnetic field to the test object. Magnetic flux concentrates on defects such as cracks on the surface of the test object, and the magnetic powder is attracted to this magnetic flux, forming an indication pattern by the magnetic powder. The defects are then inspected by observing this magnetic powder indication pattern. Magnetic particle testing includes fluorescent magnetic particle testing, which uses fluorescent magnetic powder containing a phosphor in the magnetic powder to improve the accuracy of defect detection.

On the other hand, in penetrant testing, a penetrant liquid is first applied to the surface of the object to be inspected, and the penetrant liquid is allowed to penetrate into defects such as cracks on the surface. Next, excess penetrant liquid adhering to the surface is removed, and developer powder is applied to the surface, and the penetrant liquid that has penetrated into the defects is sucked to the surface by capillary action. The defects are then inspected by observing the penetration indication pattern created by the sucked up penetrant liquid. One type of penetrant testing is fluorescent magnetic particle testing, which uses a fluorescent penetrant liquid containing a phosphor to improve the accuracy of defect detection.

When using fluorescent magnetic powder or fluorescent penetrant liquid in magnetic particle testing or penetrant testing, it is necessary to irradiate the test object with ultraviolet light to excite the fluorescent magnetic powder or fluorescent penetrant liquid contained therein. Known ultraviolet irradiation devices that irradiate ultraviolet light include those that use ultraviolet LEDs (Light Emitting Diodes) as the light source.

When focusing light from an LED using a focusing lens and then focusing the light again using a linear Fresnel lens, reflection occurs when the light focused by the LED enters the linear Fresnel lens. This creates the problem that, when ensuring illuminance using this method, excess energy must be reserved.

Patent Document 1 discloses a technology that uses a reflector to efficiently use the diffused light. In detail, Patent Document 1 discloses a technology in which multiple lens-integrated chip-type LEDs, each having a lens on both sides and above the LED, are arranged in a straight line in the direction in which the lenses are attached to both sides, multiple LED blocks arranged in a straight line are arranged in parallel, and a light reflector is attached between the LED blocks arranged in a straight line at an angle of 90 degrees or more to the lens-integrated chip-type LEDs.

The technology described in Patent Document 1 can improve energy efficiency by reflecting wasted light with a reflector, but in order to meet the requirement in non-destructive testing of ensuring a certain level of illuminance, a condenser lens is used. Furthermore, when a linear Fresnel lens is used, the light reflected from the linear Fresnel lens is appropriately re-reflected and irradiated onto the irradiated surface, and a uniform and strong light distribution on the irradiated surface is not achieved.

JP 2007-73469 A JP 2014-194914 A

In this way, when multiple lenses are used on a surface to which ultraviolet light is irradiated by an ultraviolet LED, even if reflection occurs at the second lens, the challenge is to improve energy efficiency by appropriately re-reflecting the light, thereby achieving a uniform and powerful light distribution using less energy.

Therefore, there is a need to develop an ultraviolet irradiation device that can obtain high ultraviolet irradiance and a uniform ultraviolet irradiance distribution using a small number of LEDs on the irradiated surface where ultraviolet light is irradiated by ultraviolet LEDs.

The object of the present invention is to provide an ultraviolet irradiation device that irradiates ultraviolet rays and an ultraviolet flaw inspection device that irradiates the surface of an object to be inspected with ultraviolet rays to analyze the surface condition of the object, which can achieve high ultraviolet irradiance in the irradiation area of the irradiated surface with fewer LEDs and energy, thereby improving the accuracy of ultraviolet flaw inspection.

In order to solve the above problems, the ultraviolet irradiation device of the present invention is an ultraviolet irradiation device including an ultraviolet LED that irradiates an irradiated surface with ultraviolet light, a condensing lens that condenses light rays emitted from the ultraviolet LED, and a linear Fresnel lens that causes incident light rays that have passed through the condensing lens to be incident on the linear Fresnel lens and further condenses the light in only one arbitrary direction on the irradiated surface,
When an XYZ three-dimensional orthogonal coordinate system is used, with the center of the ultraviolet LED light source as the origin, the direction parallel to any one direction on the irradiated surface as the X-axis direction, the direction on the irradiated surface perpendicular to the X-axis direction as the Y-axis direction, and the direction parallel to the optical axis of the ultraviolet LED perpendicular to the X-axis direction and the Y-axis direction as the Z-axis direction,
the linear Fresnel lens is a lens that collects light only in the X-axis direction, and is located between the ultraviolet LED and the irradiated surface in the negative direction of the Z-axis;
In an ultraviolet irradiation device, the irradiated surface is located a predetermined distance away from the linear Fresnel lens in the negative direction of the Z axis,
The linear Fresnel lens is disposed on an XZ plane on which the X-axis and the Z-axis exist, at an angle of 25 degrees with respect to the Z-axis, and is disposed inside each of two imaginary straight lines passing through the origin,
or
The linear Fresnel lens has a pair of imaginary lines passing through an origin on an XZ plane, the angle between the imaginary line and the Z axis being 25 degrees and a pair of imaginary lines being 30 degrees, in the negative Z direction, and has a pair of imaginary lines in the positive X direction and a pair of imaginary lines in the negative X direction, and has a vertically elongated slit that is long in the Y direction between the 25 degree imaginary line and the 30 degree imaginary line of each of the two pairs of imaginary lines;
Furthermore, the ultraviolet irradiation device is provided with a reflector, and the reflector is provided so as to be capable of re-reflecting reflected light rays, which are reflected by the linear Fresnel lens along two imaginary straight lines passing through the origin on the XZ plane and making an angle of 30 degrees with the Z axis, from the linear Fresnel lens, and which are the two outermost light rays, together with surrounding light rays, pass through the outside of the linear Fresnel lens or pass through the vertically elongated slit.

Furthermore, the ultraviolet irradiation device of the present invention is characterized in that the ultraviolet irradiation device further includes a housing that surrounds the ultraviolet LED and the linear Fresnel lens and has an ultraviolet outlet through which ultraviolet light emitted from the ultraviolet LED is emitted, and an ultraviolet transmission filter capable of blocking visible light is disposed in the ultraviolet outlet.

The ultraviolet irradiation device of the present invention is an ultraviolet irradiation device including an ultraviolet LED that irradiates an irradiated surface with ultraviolet light, a condensing lens that condenses light rays emitted from the ultraviolet LED, and a linear Fresnel lens that causes incident light rays that have passed through the condensing lens to be incident on the linear Fresnel lens and further condenses the light in only one arbitrary direction on the irradiated surface,
When an XYZ three-dimensional orthogonal coordinate system is used, with the center of the ultraviolet LED light source as the origin, the direction parallel to any one direction on the irradiated surface as the X-axis direction, the direction on the irradiated surface perpendicular to the X-axis direction as the Y-axis direction, and the direction parallel to the optical axis of the ultraviolet LED perpendicular to the X-axis direction and the Y-axis direction as the Z-axis direction,
the linear Fresnel lens is a lens that collects light only in the X-axis direction, and is located between the ultraviolet LED and the irradiated surface in the negative direction of the Z-axis;
In an ultraviolet irradiation device, the irradiated surface is located a predetermined distance away from the linear Fresnel lens in the negative direction of the Z axis,
The linear Fresnel lens is disposed on an XZ plane on which the X-axis and the Z-axis exist, at an angle of 25 degrees with respect to the Z-axis, and is disposed inside each of two imaginary straight lines passing through the origin,
or
The linear Fresnel lens has a pair of imaginary lines passing through an origin on an XZ plane, the angle between the imaginary line and the Z axis being 25 degrees and a pair of imaginary lines being 30 degrees, in the negative Z direction, and has a pair of imaginary lines in the positive X direction and a pair of imaginary lines in the negative X direction, and has a vertically elongated slit that is long in the Y direction between the 25 degree imaginary line and the 30 degree imaginary line of each of the two pairs of imaginary lines;
Furthermore, the ultraviolet irradiation device includes a reflector, and the reflector is arranged so that, among the incident light rays that pass through the origin on the XZ plane and enter the inner side of the linear Fresnel lens of two virtual straight lines that form an angle of 30 degrees with the Z axis, the two outermost light rays are reflected from the linear Fresnel lens, and the reflected light rays, together with the surrounding light rays, pass through the outside of the linear Fresnel lens or the vertically elongated slit. Therefore, the light emitted from the ultraviolet LED passes through a condenser lens, enters the linear Fresnel lens as an incident light ray, and among the reflected light, the reflected light of the light ray that enters the linear Fresnel lens at an angle at which the intensity is relatively strong as a light ray at a half-value angle is reflected again by the reflector, and the light irradiates the irradiated surface directly without passing through a lens, so that high ultraviolet irradiance can be secured in the irradiation area of the irradiated surface while improving energy efficiency.

Furthermore, in the ultraviolet irradiation device of the present invention, the ultraviolet irradiation device further includes a housing that surrounds the ultraviolet LED and the linear Fresnel lens and has an ultraviolet outlet through which ultraviolet light emitted from the ultraviolet LED is emitted, and the ultraviolet outlet is characterized in that an ultraviolet transmission filter capable of blocking visible light is disposed at the ultraviolet outlet, making it possible to block visible light, improving the working environment compared to when visible light is irradiated and contributing to preventing inspectors from overlooking scratches caused by visible light.

1 is a schematic front view of an ultraviolet irradiation device 1 according to an embodiment of the present invention. FIG. 2 is a side view of FIG. 1 showing the ultraviolet irradiation device 1 according to the present embodiment. FIG. 2 is an explanatory diagram showing an enlarged view of the portion from the ultraviolet LED 6 to the linear Fresnel lens 3 in FIG. 1 for mainly explaining the light beam. FIG. 3 is an explanatory diagram for explaining the present invention using imaginary straight lines 11 and 12. 10 is an enlarged view for explaining a portion from an ultraviolet LED 6 to a linear Fresnel lens 3 in another example of an ultraviolet irradiation device 1 according to the present invention. FIG. 5. (X) is a top view of the linear Fresnel lens 3 in FIG. 5, (Y) is a side view thereof, and (Z) is a front view thereof.

The details of the embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional side view in the width direction (X-axis direction) showing an example of an ultraviolet irradiation device 1 according to this embodiment, and FIG. 2 is a cross-sectional side view in the longitudinal direction (Y-axis direction) perpendicular to the width direction of the ultraviolet irradiation device 1 of FIG. 1. FIG. 3 is an enlarged view of the ultraviolet irradiation device 1 of FIG. 1 as seen in the width direction as in FIG. 1, mainly explaining the trajectory of the light beam at the so-called half-value angle, FIG. 4 is an explanatory diagram showing the size of the linear Fresnel lens 3 of the present invention as seen in the width direction using a virtual straight line, and FIG. 5 is an explanatory diagram of another example of the ultraviolet irradiation device 1, in which the slit 20 of the linear Fresnel lens 3, which is a part different from FIG. 4, is explained using virtual straight lines 12, 13, 14, and 15. FIG. 6 shows a top view, a side view, and a front view of the linear Fresnel lens 3 of FIG. 5, respectively, in (X), (Y), and (Z). In this disclosure, the X direction is the horizontal direction in FIG. 1, as shown in FIG. 1, and the positive direction in the X direction is shown as +X on the right side of FIG. 1, and the negative direction is shown as -X. The width direction is the X direction, and a diagram showing the width direction is a diagram in which the X direction is taken as the horizontal axis. The same is true for the Y and Z directions. The origin of these X, Y and Z axes is the center O of the ultraviolet LED 6 light source, and is shown in FIG. 1 to FIG. 5.

First, when fluorescent magnetic powder or fluorescent penetrant liquid is used in magnetic particle inspection or penetrant inspection, the ultraviolet irradiation device 1 irradiates the surface of the object to be inspected with ultraviolet light in order to excite the fluorescent magnetic powder or fluorescent penetrant liquid contained therein. It is equipped with an ultraviolet LED 6 that irradiates the irradiated surface 4 with ultraviolet light, and a linear Fresnel lens 3 that focuses the light in any one direction (width direction) on the irradiated surface 4.

The ultraviolet irradiation device 1 may further include a housing (not shown) that surrounds the ultraviolet LED 6 and the linear Fresnel lens 3 and has an ultraviolet light outlet through which the ultraviolet light emitted from the ultraviolet LED 6 is emitted. It is preferable to place an ultraviolet light transmission filter capable of blocking visible light at the ultraviolet light outlet. This ultraviolet light transmission filter cuts the slight visible light emitted from the ultraviolet LED 6 in the visible light wavelength range of approximately 400 nm to 700 nm, and can improve the inspection work by preventing the visible light from being reflected by the metallic glossy surface and dazzling the worker when inspecting the metallic glossy surface of the surface of the inspection object cut by a grinder or the like to detect defects in the inspection object.

As shown in FIG. 1, the linear Fresnel lens 3 is a lens that focuses light in the X direction and is located between the ultraviolet LED 6 and the irradiated surface 4 in the negative direction of the Z axis, and the irradiated surface 4 is located a predetermined distance away from the linear Fresnel lens 3 in the negative direction of the Z axis.

The linear Fresnel lens 3 is formed by dividing the surface of a kamaboko-shaped lens (e.g., a cylindrical lens) into sections by multiple straight lines, and by specially adjusting the Fresnel angle of each Fresnel surface in a lens with steps between adjacent sections to make the height of each section (Fresnel surface) roughly uniform. In addition, the linear Fresnel lens 3 has Fresnel surfaces and rise surfaces for creating the steps formed alternately. The configuration for adjusting the Fresnel angle will be described in detail later.

To form such Fresnel surfaces and rise surfaces, multiple grooves are formed linearly and parallel to each other (and parallel to the Y-axis direction) on one surface of the linear Fresnel lens 3. Each groove is composed of a pair of one Fresnel surface and one rise surface.

Each of these Fresnel surfaces is a surface that matches the shape of an aspheric lens, and each of the rise surfaces is a roughly flat surface that rises almost perpendicular to the smooth surface 24, which is the upper surface of the linear Fresnel lens 3.

The linear Fresnel lenses 3, 70 are plane-symmetrical with respect to the central plane. The central plane is perpendicular to the top surface of the linear Fresnel lenses 3, 70 and parallel to the grooves, and is located at the center of the linear Fresnel lenses 3, 70 in the X direction.

Since the linear Fresnel lenses 3 and 70 are plane-symmetrical with respect to the central plane, the orientation of each groove arranged on one side of the central plane is opposite to the orientation of each groove arranged on the other side of the central plane. More specifically, as shown in FIG. 6, on one side, each Fresnel surface is inclined so as to descend toward the right (positive direction of the X-axis), while on the other side, each Fresnel surface is inclined so as to descend toward the left (negative direction of the X-axis).

Figure 1 shows an ultraviolet irradiation device 1 further equipped with a reflector 5. An ultraviolet LED 6 is located at position O, and a linear Fresnel lens 3 is located in the negative direction of the Z axis, i.e., vertically. Two reflectors 5 are provided in the width direction of O so as to surround O and reflect light inward, more specifically, in approximately the same direction as the linear Fresnel lens 3.

The ultraviolet irradiation device 1 will be described in more detail with reference to FIG. 1. First, a light beam is emitted from an O ultraviolet LED 6 as a light source, and is focused by a focusing lens 2 as shown in FIG. 3. This focused light beam is the incident light beam 10. As shown in FIG. 1 and FIG. 3, this incident light beam 10 is reflected by the linear Fresnel lens 3, and a part of it is incident on the reflector 5. When the incident light beam 10 near the half-value angle described later is reflected by the linear Fresnel lens 3, the reflector 5 is located in a position where it can re-reflect the reflected light beam. Furthermore, the reflector 5 is located in a position where the re-reflected light beam passes outside the linear Fresnel lens 3, and the part of the incident light beam 10 that entered the linear Fresnel lens 3 and is focused by the linear Fresnel lens 3 that irradiates the irradiated surface 4 and the irradiation area on the irradiated surface 4 completely or almost overlap with the re-reflected light beam, and the irradiation area on the irradiated surface 4 is located directly without passing through the linear Fresnel lens 3. This prevents the light rays reflected by the reflector 5 from being reflected again by the linear Fresnel lens 3, improving energy efficiency.

In FIG. 2, a side view showing the Y direction in FIG. 1 is shown. The reflector 5 is indicated by a dotted line on the top of the linear Fresnel lens 3. The reflection range 50 is the irradiation range on the linear Fresnel lens 3 of the light that enters the linear Fresnel lens 3 and passes through the condenser lens 2 when the half-value angle between the ultraviolet LED 6 and the condenser lens 2 is 40 degrees. At this time, it is preferable that the width of the reflector 5 is wider than the length of the reflection range 50, and that the reflection range 50 fits within the width of the reflector 5 in the Y direction. This allows the light reflected from the linear Fresnel lens 3 to be effectively reflected again. The length of the reflector 5 in the Y direction is longer than the length of the reflection range 50 in the Y direction, and the reflection range 50 fits within the length of the reflector 5 in the Y direction, so that the incident light 10 can be effectively reflected again. Table 1 shows the reflectance by the linear Fresnel lens 3 near the half-value angle, that is, the energy loss. The half-value angle is when the angle of incidence on the linear Fresnel lens 3 is approximately 50 degrees. In this case, referring to Table 1, approximately 11.266 percent is reflected, which would be wasted energy in a conventional configuration. This embodiment discloses a configuration that makes use of this.

Next, the trajectory of the light beam at the half-value angle will be described in more detail with reference to FIG. 3. FIG. 3 is a cross-sectional view in the XZ plane. The Fresnel surface and the rise surface of the linear Fresnel lens 3 are omitted. First, the light emitted from the ultraviolet LED 6 is condensed by the condenser lens 2, and then enters the smooth surface 24 of the linear Fresnel lens 3 as the incident light beam 10. Of the incident light beam 10, the light beam at an angle equal to or greater than an angle at which the relative radiant intensity of the irradiated light beam is less than half as a characteristic of the condenser lens has a characteristic that the ultraviolet intensity drops sharply. For this reason, it is common to utilize ultraviolet light up to the half-value angle. The imaginary straight lines 41 and 42 are imaginary straight lines extending from the origin O, which is the center of the light source, and making an angle α with respect to the Z axis, which indicate the light beam at the half-value angle. Then, the light beam shown as the incident light beam 10 in FIG. 3, which is light within the range of the imaginary straight lines 41 and 42 indicating the light beam at the half-value angle on the smooth surface 24 of the linear Fresnel lens 3, is partially reflected by the linear Fresnel lens 3 as the reflected light beam 11. In this case, it is preferable that the reflector 5 is located on the straight line that indicates the locus of the reflected light of the outermost light ray within the range of the imaginary straight lines 41 and 42 among the light rays that are incident on the linear Fresnel lens 3. This allows the reflector 5 to accurately capture light rays that are relatively strong near the half-value angle and that are easy to transmit the light that is re-reflected outside the linear Fresnel lens 3.
Generally, when an ultraviolet LED and a convex lens are used, the half-value angle of the angle α is about 40 degrees. In other words, when such directional characteristics are present, the angle α is 20 degrees.
The reflected light ray 11 is then further reflected again by the reflector 5, and is a ray in the vicinity of the outermost ray of the incident light ray 10 within the range of the imaginary straight lines 41, 42, specifically, the light reflected by the linear Fresnel lens 3 at approximately 18 degrees to 21 degrees when the vertical direction from the origin O is set to 0 degrees on the XZ plane. The light ray emitted from the ultraviolet LED 6 is also reflected again by the reflector 5, and the range of these rays is the re-reflected beam 60, which is the range shown as between the lines 61 and 62.

Next, the range in which the linear Fresnel lens 3 is located will be described using FIG. 4 together with FIG. 3. FIG. 4 is a diagram showing that the linear Fresnel lens 3 is located inside the imaginary straight lines 12 and 13 that pass through the origin O on the XZ plane on which the X-axis and Z-axis exist, which is the same viewpoint as FIG. 3, and that make an angle β of 25 degrees with the Z-axis. The re-reflected light rays 43 and 44 shown in FIG. 3 represent the light rays when the incident light ray 10 at the half-value angle is re-reflected by the reflector 5. As shown in FIG. 4, when the linear Fresnel lens 70 is installed approximately horizontally, the imaginary straight lines 12 and 13 pass through the origin O on the XZ plane and make an angle β of 25 degrees with the Z-axis. The linear Fresnel lens 3 is located between the imaginary straight lines 12 and 13, and therefore there is no linear Fresnel lens 3 outside the imaginary straight lines 12 and 13. This is advantageous because the re-reflected beam 60, which is a bundle of light rays surrounded by lines 61 and 62 and is a light ray near the re-reflected light ray 43, can pass outside the linear Fresnel lens 3 and directly irradiate the irradiated surface 3 (not shown in FIG. 4) with the re-reflected light. The same is true for the re-reflected light ray 44. The same is true for the left half of FIG. 4, although not shown in detail.

As another example of the embodiment of the present invention, FIG. 5 shows a case where a linear Fresnel lens 70 as shown in FIG. 6 is used in the ultraviolet irradiation device 1. The linear Fresnel lens 70 in FIG. 5 has a slit 20. The position of the reflector 5 is the same as that in FIG. 4. When the linear Fresnel lens 70 is installed substantially horizontally, the slit 20 is surrounded by imaginary straight lines 12 and 13 that pass through the origin O on the XZ plane and have an angle β of 25 degrees with the Z axis, and imaginary straight lines 14 and 15 that pass through the origin O on the XZ plane and have an angle Θ of 30 degrees with the Z axis, and has a width wider than the width of the area 30 on the smooth surface 24 of the linear Fresnel lens 3. Referring to FIG. 6, it is the short side 21 that has a width wider than this area 30. However, the slit 20 does not necessarily have to be rectangular as shown in FIG. 6, and may have a different shape such as an elliptical shape as long as the width is secured. The slit 20 also has a long side 22 that extends in the Y direction. Even if the shape of the slit is not rectangular, it is still a slit that is long in the Y direction. Also, in FIG. 6, the linear Fresnel lens 70 has a smooth surface 24 and a surface 23 having a Fresnel. The surface 23 having a Fresnel faces downward, and the smooth surface 24 faces upward in the direction of the ultraviolet LEDs 6, and as shown in FIG. 1 etc., it is installed approximately horizontally in the ultraviolet irradiation device 1. This is the same for the linear Fresnel lens 3, except for the description of the slit 20.

In the slit 20 shown in FIG. 5, as in FIG. 4, the light reflected from the linear Fresnel lens 70 at the half-value angle is reflected again by the reflector 5. The re-reflected light is reflected in the same manner as in FIG. 4, and the part corresponding to the re-reflected beam 60 in FIG. 4 passes through the slit 20. The re-reflected beam 60 is incident on the inner area of the slit 20 of the linear Fresnel lens 70 from the ultraviolet LED 6, and is positioned so that the irradiation range completely or almost overlaps with the irradiation area on the irradiated surface 4 irradiated by the light that passed through the linear Fresnel lens 70, and the re-reflected beam 60 is configured to directly irradiate the irradiated surface 4 without passing through the linear Fresnel lens 70.

Returning to FIG. 1, the dimensions of the irradiated surface 4 will be described. The dimensions of the irradiated surface 4 are not limited, but for example, when the distance from the linear Fresnel lens 3, 70 to the irradiated surface 4 is 600 mm and the irradiated width in the width direction of the irradiated surface in FIG. 1 is 50 mm to 200 mm, the Fresnel angle near the center (zero point) in the X direction is preferably 4 degrees to 37 degrees from the viewpoint of uniform irradiation in the width direction. Also, the Fresnel angle at both ends in the width direction is preferably 22 degrees to 52 degrees from the viewpoint of uniform irradiation in the width direction.

Here, typical dimensions and materials of the linear Fresnel lenses 3, 70 of the present invention will be described. The length of one side in the X direction of each groove in the linear Fresnel lens 3 is approximately 0.3 mm. The size of each Fresnel surface and rise surface is such that the length of the Fresnel surface in the X direction is approximately 0.25 mm to 0.40 mm, and the height of the rise surface in the Z axis direction is approximately 0.05 mm to 0.15 mm. In this case, approximately 162 Fresnel surfaces and rise surfaces are formed on the linear Fresnel lens 3. Note that these dimensions are not limited, and can be designed appropriately from the viewpoint of obtaining a uniform ultraviolet irradiance distribution.

The linear Fresnel lenses 3 and 70 can be made of conventionally used transparent resins, such as acrylic resin, epoxy resin, polycarbonate resin, polyester resin, styrene resin, acrylic-styrene copolymer resin, cycloolefin polymer resin, and silicone resin. These resins can be molded using a mold having the inverse shape of the Fresnel lens by a method such as press molding or polymerization molding.

The linear Fresnel lens 3 used in the ultraviolet irradiation device 1 of Example 1 is made of acrylic resin, and is fabricated by machining with a face length of 50 mm, a thickness t of 0.3 mm, and a pitch of 0.3 mm, with the Fresnel angle varying continuously from 14.047 degrees to 47.192 degrees, for the purpose of uniforming the ultraviolet irradiance in an irradiation range of 200 mm in the X direction of the irradiated surface located at a distance of 600 mm from the improved linear Fresnel lens. The ultraviolet LED 6 used has a peak wavelength of 365 nm.
<Evaluation method>
(UV irradiance distribution test)
The ultraviolet irradiance distribution of the irradiated surface was measured when the ultraviolet irradiation device 1 of Example 1 was used. The ultraviolet irradiance distribution was measured in an area of 200 mm irradiation width in the X-axis direction of the irradiated surface located at a distance of 600 mm from the improved linear Fresnel lens, and the degree of improvement of the ultraviolet irradiance distribution was measured. The method of measuring the degree of improvement was to compare the uniform irradiance when the ultraviolet irradiance was within a range of ±10% of the average ultraviolet irradiance over the entire irradiation width and the ultraviolet irradiance was uniform.

The comparative example had the same configuration as the invention disclosed herein, and had the UV LED 6 and the condenser lens 2 arranged in the same manner as in Example 1. However, the linear Fresnel lens did not have the features of the present invention, namely, the linear Fresnel lens is contained within the range of the imaginary straight lines 12 and 13, a slit is provided in the linear Fresnel lens, and a reflector 5 is provided.

The results of comparing the illuminance in this UV irradiance measurement test were as follows. In other words, if the UV irradiance result of the comparative example is taken as 100%, the UV irradiance obtained on the irradiated surface 4 in the example was approximately 105 to 115%.

The present disclosure can be suitably used in an ultraviolet irradiation device that irradiates ultraviolet rays, and an ultraviolet flaw detection device equipped with an ultraviolet irradiation device. However, the present disclosure is not limited to the above-described embodiment and examples. The ultraviolet irradiation device of the present disclosure is useful for all tests and inspections that use ultraviolet rays, such as contamination checks, leakage inspections, and confirmation of degreasing and cleaning. In addition, the ultraviolet flaw detection device of the present disclosure is not limited to a fluorescent magnetic particle flaw detection device, but may be a penetrant flaw detection device that uses a fluorescent penetrant to detect flaws on the surface of an object to be inspected, and can be applied to all ultraviolet flaw detection devices that use ultraviolet rays to detect flaws.

Reference Signs List 1: UV irradiation device 2: Condenser lens 3, 70: Linear Fresnel lens 4: Irradiated surface 5: Reflector 6: UV LED
10 Incident light ray 11 Reflected light ray 12, 13, 14, 15 Imaginary straight line 20 Slit 21 Short side 22 Long side 23 Surface having Fresnel 24 Smooth surface 30 Area 41, 42 Imaginary straight lines 43, 44 Re-reflected light ray 60 Re-reflected beam

Claims (2)

An ultraviolet irradiation device comprising: an ultraviolet LED that irradiates an irradiated surface with ultraviolet light; a condensing lens that condenses light emitted from the ultraviolet LED; and a linear Fresnel lens that causes an incident light beam that has passed through the condensing lens to enter the linear Fresnel lens and further condenses the light beam in only one arbitrary direction on the irradiated surface,
When an XYZ three-dimensional orthogonal coordinate system is used, with the center of the ultraviolet LED light source as the origin, the direction parallel to any one direction on the irradiated surface as the X-axis direction, the direction on the irradiated surface perpendicular to the X-axis direction as the Y-axis direction, and the direction parallel to the optical axis of the ultraviolet LED perpendicular to the X-axis direction and the Y-axis direction as the Z-axis direction,
the linear Fresnel lens is a lens that collects light only in the X-axis direction, and is located between the ultraviolet LED and the irradiated surface in the negative direction of the Z-axis;
In an ultraviolet irradiation device, the irradiated surface is located a predetermined distance away from the linear Fresnel lens in the negative direction of the Z axis,
The linear Fresnel lens is disposed on an XZ plane on which the X-axis and the Z-axis exist, at an angle of 25 degrees with respect to the Z-axis, and is disposed inside each of two imaginary straight lines passing through the origin,
or
The linear Fresnel lens has a pair of imaginary lines passing through an origin on an XZ plane, the angle between the imaginary line and the Z axis being 25 degrees and a pair of imaginary lines being 30 degrees, in the negative Z direction, and has a pair of imaginary lines in the positive X direction and a pair of imaginary lines in the negative X direction, and has a vertically elongated slit that is long in the Y direction between the 25 degree imaginary line and the 30 degree imaginary line of each of the two pairs of imaginary lines;
The ultraviolet irradiation device further includes a reflector, and the reflector is provided so as to be capable of re-reflecting reflected light beams, which are reflected by the linear Fresnel lens along two imaginary straight lines passing through the origin on an XZ plane and making an angle of 30 degrees with the Z axis, and in which the two outermost light beams are reflected from the linear Fresnel lens, together with surrounding light beams, so as to pass through the outside of the linear Fresnel lens or the vertically elongated slit. The ultraviolet irradiation device further includes a housing that surrounds the ultraviolet LED and the linear Fresnel lens and has an ultraviolet light outlet through which ultraviolet light emitted from the ultraviolet LED is emitted, and an ultraviolet light transmitting filter capable of blocking visible light is disposed in the ultraviolet light outlet.
2. The ultraviolet irradiation device according to claim 1.

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