Light irradiation device

Abstract

To provide a light irradiation device 100 that is configured to be capable of switching the separation recommendation distance and can reduce the number of switching stages as few as possible in switching.SOLUTION: A light irradiation device includes: a light source body 2; and a lens 3 for condensing light emitted from the light source body 2. An optical constant of the lens 3 is set such that condensation position of light from the light source body 2 changes continuously or step-by-step along on a lens optical axis C as proceeding from the center to an outer edge of the lens 3.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a light emitting device used in a surface inspection device, an exposure device, or the like, and more particularly to a light irradiation device having one or more light source bodies such as LEDs. [Background technology]

[0002] As an example of this type of light irradiation device, as shown in Patent Document 1, a so-called line light irradiation type is known in which light is emitted from multiple LEDs arranged in series through a rod lens and a line or band of light is irradiated onto the workpiece.

[0003] For such light irradiation devices, a recommended separation distance for placing a workpiece is specified. This recommended separation distance is the distance at which the light emitted from the light irradiation device is focused, in other words, the distance at which the LED forms an image, and this distance is determined by the focal length of the lens and the distance between the LED and the lens.

[0004] Also, for the purpose of enabling one model to handle various surrounding conditions in which the workpiece or light irradiation device is installed, a light irradiation device that allows the distance between the lens and the LED to be variable and the recommended separation distance to be adjusted is being considered. In reality, it is difficult to continuously change the long LED board or lens while maintaining its parallelism, so a light irradiation device that has a structure that allows the distance between the lens and the LED to be switched in multiple steps and that is configured to allow the recommended separation distance to be switched in multiple steps is being considered.

[0005] The dashed lines in Figure 12 show the theoretical change in irradiance at each recommended separation distance when the distance between the LED and the lens is changed to change the recommended separation distance. In other words, the dashed lines show the maximum irradiance curves that can be obtained by optimizing the distance between the LED and the lens at each separation distance.

[0006] On the other hand, the irradiance peaks at the aforementioned recommended isolation distance, and decreases as the distance between the work and the light irradiation device becomes longer or shorter than that. The solid line in the figure qualitatively shows the change in irradiance when the distance between the LED and the lens is fixed. The peak position of this solid line is the recommended isolation distance when the distance between the LED and the lens is fixed. Also, it can be seen from the figure that the angle of the peak becomes smaller as the recommended isolation distance is decreased.

[0007] In the light irradiation device capable of switching the recommended isolation distance in multiple steps as described above, even if the isolation distance between the work and the light irradiation device is arbitrarily changed, by setting it to the recommended isolation distance of any stage, at least the minimum guaranteed irradiance at each isolation distance can be ensured. In this case, the value of the recommended isolation distance and the number of switching stages to be set are uniquely determined. In the figure, the required number of stages is six.

[0008] However, as the number of switching stages increases, it becomes exponentially more difficult to ensure the dimensional accuracy of the lens-LED distance at each stage. This not only complicates the switching structure but also causes problems such as an increased burden on production management.

[0009] Such problems are not limited to line light irradiation type light irradiation devices.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] Therefore, the present invention has been made in view of the above-described problems, and provides a light irradiation device configured using a light source body such as one or more LEDs, which is configured to be able to switch the recommended isolation distance and to minimize the number of switching stages at that time.

Means for Solving the Problem

[0012] That is, the light irradiation device according to the present invention is as follows.

[0013] [1] It includes a light source body and a lens that condenses the light emitted from the light source body, The optical constants of the lens are set such that the light condensing position from the LED changes continuously or stepwise along the lens optical axis as it goes from the center to the outer edge of the lens. A light irradiation device characterized by this.

[0014] According to such a configuration, it is possible to reduce the degree of change in irradiance accompanying a change in the isolation distance between the workpiece and the light irradiation device. Therefore, it is possible to secure a range of isolation distances that can be used while ensuring a constant irradiance before and after the recommended isolation distance. Furthermore, when configured to be able to switch the recommended isolation distance while ensuring a constant irradiance, it becomes possible to reduce the number of switching steps.

[0015] That is, while simplifying the configuration, it is possible to ensure the necessary irradiance on the workpiece.

[0016] Note that the optical constants of the lens include at least one or more of the curvature / refractive index / thickness / number of sheets / installation position / front and back / aspherical coefficient / conic constant of the lens. Also, the light condensing position is the position where the light beam diameter is the smallest, and the light beam diameter is the diameter at which, in a cross-section perpendicular to the optical axis, irradiance equal to or higher than a certain ratio (for example, 1 / e 2 ) or more can be obtained.

[0017] [2] The light irradiation device according to [1], further comprising a distance variable structure that enables the distance between the lens and the LED to be changed stepwise.

[0018] If it is such a thing, it can have a simple structure and can switch the recommended isolation distance.

[0019] [3] The optical constant of the lens is set such that the closer the light passes through the central portion of the lens, the closer its focusing position is to the lens, according to the light irradiation device described in [1] or [2].

[0020] Such a configuration can be realized, for example, by setting the curvature of the central portion of the lens to be larger than the curvature of the outer region thereof. As a result, the flange thickness can be increased and the central thickness can be decreased, facilitating the manufacture of the lens. Specifically, not only does the eccentricity ratio (central thickness / flange thickness) decrease and the injection moldability improve, but also the volume can be reduced, so that the manufacturing cost can be suppressed.

[0021] [4] The lens is divided into a plurality of zones between the center and the outer edge, and the curvature in each zone is made different, according to the light irradiation device described in any one of [1] to [3].

[0022] With such a configuration, performance and sizes that cannot be achieved with a continuously smooth lens surface can be realized, and the degree of freedom in design can be increased. Here, the curvature in each zone is, for example, the curvature at the center of each zone.

[0023] [5] The curvature of the lens surface on which the light beam closest to being parallel to the optical axis of the lens is incident is made different in each of the above zones, according to the light irradiation device described in [4].

[0024] With such a configuration, even if a step is formed at the boundary between adjacent zones, the light quantity loss and the generation of stray light due to the step can be suppressed as much as possible. In addition, the viewing angle (collimation half angle) of the light source as seen from a point on the lens surface defining each zone can be set as small as possible. As a result, it is not necessary to take care of the light incident obliquely, and it is less affected by manufacturing variations, and a plurality of focusing positions can be set more accurately in the lens optical axis direction.

[0025] [6] A linear or strip-shaped light extending along a predetermined direction is irradiated onto the workpiece, A plurality of the light source bodies are provided aligned along the predetermined direction, The light irradiation device described in any one of [1] to [5], wherein the lens has no curvature in the specified direction and has curvature in a plane perpendicular to the specified direction, and focuses light components emitted from the light source and traveling along the perpendicular plane.

[0026] This configuration is the application of the present invention to a line light irradiation type light irradiation device equipped with a long lens or substrate, and as a result of being able to reduce the number of switching steps of the recommended separation distance, the effect of the present invention in terms of simplifying the configuration is remarkable.

[0027] [7] The light irradiation device described in [6], wherein the first requirement is that when viewed from the specified direction, the area on the positive side of the aberration curve shown in a longitudinal aberration diagram, with the origin at the intersection of the optical axis of the lens and the surface of the workpiece, the optical axis on the horizontal axis with the direction in which light travels on the positive side, and the vertical axis on the normalized pupil coordinates, is larger than the area on the negative side, and the optical constants of the lens are determined so that this first requirement is further satisfied.

[0028] Such a configuration makes it possible to maximize the irradiance on the work surface. Also, since it is possible to eliminate anything that does not meet the first requirement, the optical design becomes easier.

[0029] [8] The light irradiation device according to [6] or [7], wherein the second requirement is that the sum of the slopes of the aberration curve at each point spaced apart by an infinitesimal distance is positive, and the optical constants of the lens are determined so as to further satisfy this second requirement.

[0030] In such a case, it can be set so that the degree of decrease in irradiance before and after the distance at which the irradiance is maximized, that is, the recommended installation distance, is substantially symmetric. Therefore, even if the separation distance between the work and the light irradiation device deviates to either side of the recommended installation distance due to an arrangement error or the like, a rapid decrease in irradiance can be prevented.

Advantages of the Invention

[0031] According to the present invention configured as described above, the degree of change in irradiance accompanying a change in the separation distance between the work and the light irradiation device can be reduced. Therefore, when configured to be able to switch the recommended separation distance while ensuring the minimum guaranteed irradiance, the number of switching steps can be made smaller.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0033] An embodiment of the present invention will be described below with reference to the drawings.

[0034] The light irradiation device 100 according to the present embodiment is a line light irradiation type that irradiates a workpiece with linear or linearly strip-shaped light (hereinafter also referred to as line light), and is referred to as a line illumination device or a bar illumination device.

[0035] As shown in FIGS. 1 and 2, this light irradiation device 100 includes a substrate 1, an LED 2 serving as a light source body, a lens 3, a distance variable structure 5 capable of stepwise changing the distance between the lens 3 and the LED 2, and a housing 4 that houses these.

[0036] Each part will be described.

[0037] The substrate 1 has a linearly strip shape. As this substrate 1, a wiring board made of metal or resin is used.

[0038] The LED 2 is, for example, a surface mount type, and a plurality of LEDs 2 are mounted so as to be arranged linearly at regular intervals along the longitudinal direction of the substrate 1. Here, these LEDs 2 are arranged in a single row, but they may be arranged in multiple rows, or may be arranged at irregular intervals instead of regular intervals.

[0039] As shown in FIGS. 1 and 2, the lens 3 is of a cylindrical type having no curvature in a cross section cut along its extending direction (Z direction) and having a curvature in a cross section perpendicular to the extending direction. Its extending direction coincides with the longitudinal direction of the substrate 1, and the lens optical axis C passes through the LED 2 when viewed from the longitudinal direction, and is disposed on the LED mounting surface side of the substrate 1.

[0040] Here, two lenses are shown, but it may be one lens or three or more lenses. Also, the lens may have curvatures on both surfaces in the perpendicular cross section. Also, it may be a spherical type or an aspherical type.

[0041] Hereinafter, for convenience of explanation, the longitudinal direction of the substrate 1 or the extending direction of the lens 3 that coincides with this is also referred to as the Z direction, the lens optical axis direction when viewed from the Z direction is also referred to as the X direction, and the direction orthogonal to the X direction and the Z direction is also referred to as the Y direction. Also, FIG. 2 shows light traveling on a plane perpendicular to the Z direction (hereinafter, also referred to as the first XY plane) including any one of the LEDs 2.

[0042] As shown in FIG. 2, the distance variable structure 5 is composed of, for example, a plurality of grooves extending in the Z direction (longitudinal direction) provided on both side walls of the housing 4. By fitting the lens 3 into any of these grooves, the distance between the LED 2 and the lens 3 can be switched in multiple steps. Here, the position of the lens 31 in the first stage in the X direction is configured to be changeable, but the position of the lens 32 in the second stage may be made changeable, or both positions may be made changeable. Also, the structure may be such that the position of the substrate 1 can be changed.

[0043] The housing 4 is in the shape of a quadrangular prism or a rectangular parallelepiped that holds the substrate 1 and the lens 3 so as to have the relative positional relationship described above. An opening 41 is provided in the surface of the housing 4 facing the lens 3, and the line light is emitted from the opening 41.

[0044] In the light irradiation device 100 having such a configuration, a recommended installation distance is defined, which is the position where the work should be placed with respect to the light irradiation device 100 or the position where the light irradiation device 100 should be placed with respect to the work.

[0045] Therefore, first, the conventional recommended installation distance will be described.

[0046] Conventionally, as shown in FIG. 3, attention is paid to the light traveling on the first XY plane, that is, the light emitted from one LED (hereinafter referred to as the first LED) and not including the Z-direction component, and the distance to the condensing position where the light beam diameter of this light is the smallest is defined as the recommended installation distance. Then, the relative arrangement relationship between the work and the light irradiation device is set so as to be this recommended installation distance, or the optical constants of the lens are set so that the light is condensed at a predetermined recommended installation distance. In the figure, for ease of understanding, the light rays in the case of no aberration are shown.

[0047] However, actually, since the light including the Z-direction component is also emitted from the LED, the light from other LEDs also enters the first XY plane. For example, as shown in FIG. 4, the condensing positions of the light from the LEDs (the second LED and the third LED) adjacent to both sides of the first LED on the first XY plane are closer to the light irradiation device side than the recommended installation distance.

[0048] And FIG. 5 is a qualitative graph showing the irradiance for each isolation distance between the light irradiation device and the work surface on the first XY plane, considering other LEDs as well.

[0049] Conventionally, only the first LED has been focused on, and the position where its irradiance is maximized has been defined as the recommended installation distance. However, from the figure, it can be seen that the distance at which the combined irradiance including the light of other LEDs is maximized is shorter than the recommended installation distance and is on the side of the light irradiation device.

[0050] In this way, in the line light irradiation type light irradiation device, the fact that the position where the combined irradiance is maximized is on the side of the light irradiation device rather than the conventional recommended installation distance was first discovered by the present inventor. And in accordance with this finding, and actually, as shown in FIG. 2, in view of the fact that there is aberration, the light irradiation device 100 in this embodiment is configured.

[0051] Specifically, it is as follows.

[0052] That is, as shown in FIG. 6, consider a longitudinal aberration diagram with the origin at the intersection of the lens optical axis C and the work surface in the first XY plane, the horizontal axis being the lens optical axis C (where the direction of light propagation is the positive side), and the vertical axis being the pupil coordinates on the normalized first XY plane. And in this longitudinal aberration diagram, the first requirement is that the area on the positive side of the aberration curve of the light emitted from one LED 2 on the first XY plane is larger than the area on the negative side. The optical constants of the lens 3 (here including at least the curvature, but the optical constants excluding the curvature may also be used) or the recommended installation distance are determined so as to satisfy this first requirement.

[0053] Here, the "pupil" is an image of the aperture (the opening 41 in FIG. 2) that defines the light exit diameter when viewed from the work side.

[0054] Also, the "area on the positive side of the aberration curve" refers to the area of the region surrounded by the vertical axis passing through the origin and the aberration curve on the positive side of this vertical axis in the longitudinal aberration diagram, which is the area of "A+" in FIG. 6. Also, the "area on the negative side" refers to the area of the region surrounded by the vertical axis passing through the origin and the aberration curve on the negative side of this vertical axis, which is the area of "A-" in the same figure.

[0055] In the case of FIG. (a), there is no aberration curve on the negative side, that is, there is no region of "A-", and its area is 0, so this first requirement is satisfied. In the case of FIG. (b), since the area of "A+" is larger than that of "A-", this first requirement is also satisfied.

[0056] And by determining the recommended installation distance so as to satisfy at least the first requirement, it becomes possible to maximize the combined irradiance on the work surface.

[0057] On the other hand, as shown in FIG. 5, in the conventional configuration, the inventor has found for the first time that the (combined) irradiance on the work surface decreases rapidly in the direction away from the light irradiation device with the irradiance maximum distance as the center.

[0058] Therefore, in this embodiment, in the aberration curve, the second requirement is that the sum of the inclination values at each point separated by a minute distance is positive, and the optical constants of the lens 3 (here, including at least the curvature, but the optical constants excluding the curvature may also be used) are determined so as to satisfy this second requirement.

[0059] For example, in FIG. 6(a), since the inclination is positive over all points of the aberration curve, the second requirement is satisfied. Also, in FIG. 6(b), although there is a part where the inclination is negative in a part of the aberration curve, the inclination is positive at other points, and it is obvious that their sum is positive, so the second requirement is satisfied.

[0060] As a result, as shown in FIG. 7, it is possible to make the degree of decrease in irradiance before and after the irradiance maximum distance substantially symmetric, and it is possible to prevent the irradiance from decreasing rapidly at any of the front and rear of the irradiance maximum distance. As a result, for example, it is possible to prevent an unexpected decrease in irradiance due to an arrangement error of the work or the light irradiation device 100.

[0061] Furthermore, in this embodiment, as shown in FIG. 8, the lens 3 is divided into a plurality of zones Z1 to Z3 from the center to the outer edge, and the optical constants (here, curvature) of the lens 3 in each zone Z1 to Z3 are made different. As shown in FIG. 9, the condensing positions F1 to F3 of the light passing through each zone Z1 to Z3 are configured to change stepwise along the lens optical axis C.

[0062] Here, the curvature is set to be larger in the zone closer to the center, and the light passing through the zone closer to the center is configured such that its condensing position is closer to the lens 3. In the same figure, for the sake of convenience of explanation, the lens 3 is shown as a single unit.

[0063] Also, in this lens 3, the reason for making the curvature different in each zone is that it is the lens surface 3a (hereinafter, also referred to as the variable curvature lens surface 3a for distinction from other lens surfaces) where the light beam closest to being parallel to the lens optical axis C is incident. In FIGS. 2 and 9, the variable curvature lens surface 3a is the surface closest to the work. Note that, for example, in a plurality of consecutive lenses having a concave lens, the variable curvature lens surface is not necessarily the surface closest to the work.

[0064] In such a configuration, when changing the isolation distance between the work and the light irradiation device 100 arbitrarily and ensuring the minimum guaranteed irradiance at an arbitrary isolation distance by setting it to one of a plurality of steps or any of the recommended isolation distances, as shown in FIG. 10, the degree of decrease in irradiance before and after the recommended installation distance is low, and the peak angle of the irradiance shown by the solid line is larger than that in FIG. 12, so the number of switching steps of the recommended isolation distance can be reduced. In FIG. 10, for example, the recommended isolation distance can be reduced to three steps. In the same figure, the irradiance at a certain ratio (for example, 70%) of the maximum irradiance is set as the minimum guaranteed irradiance.

[0065] Therefore, while reducing the number of switching steps of the recommended isolation distance to simplify the configuration, it is possible to ensure the necessary irradiance on the work over a wide range of distances from the light irradiation device.

[0066] Note that the present invention is not limited to the above-described embodiment.

[0067] In the above embodiment, in the lens, a plurality of zones are set and the curvature in each zone is changed stepwise. However, other optical constants related to the lens, such as the refractive index of each zone, may be changed so that the condensing positions are different.

[0068] As shown in FIG. 11, the surface of the lens 3 in each zone Z1 to Z3 may be configured to be discontinuous like a Fresnel lens.

[0069] The curvature of the lens may be changed continuously.

[0070] In order to change the recommended isolation distance in multiple steps, a plurality of lenses with different curvatures may be prepared and configured to be interchangeable.

[0071] The recommended isolation distance may be configured to be changed continuously.

[0072] Either the first requirement or the second requirement may be satisfied.

[0073] The light source body is not limited to the LED, and other light source bodies such as a semiconductor laser may be used.

[0074] Furthermore, the present invention is not limited to the line light irradiation type, and is also applicable to a light irradiation device composed of one light source body.

[0075] In addition, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit thereof.

Explanation of Reference Numerals

[0076] 100 ··· Light irradiation device 2 ··· LED (light source body) 3 ··· Lens Z1 to Z3 ··· Zones F1 to F3 ··· Condensing positions 5 ··· Distance variable structure

Claims

1. A light source body and a lens that collects light emitted from the light source body, A light irradiation device characterized in that the optical constants of the lens are set so that the focusing position of the light from the LED changes continuously or stepwise along the optical axis of the lens as it moves from the center of the lens to the outer edge.

2. 2. The light irradiation device according to claim 1, further comprising a distance variable structure that enables the distance between the lens and the LED to be changed in stages.

3. 2. The light irradiation device according to claim 1, wherein the optical constants of said lens are set so that the more light passes through the center of said lens, the closer the focusing position of said light becomes to said lens.

4. 2. The light irradiation device according to claim 1, wherein the lens is divided into a plurality of zones between the center and the outer edge, and each zone has a different curvature.

5. 5. The light irradiation device according to claim 4, wherein the curvature of the lens surface onto which the light beam most nearly parallel to the optical axis of the lens is incident is made different for each of the zones.

6. A linear or strip-shaped light extending along a predetermined direction is irradiated onto the workpiece, A plurality of the light source bodies are provided aligned along the predetermined direction, 2. The light irradiation device according to claim 1, wherein the lens has no curvature in the predetermined direction and has a curvature in a plane perpendicular to the predetermined direction, and focuses light components emitted from the light source and traveling along the perpendicular plane.

7. 7. The light irradiation device according to claim 6, wherein the first requirement is that, when viewed from the specified direction, the area on the positive side of an aberration curve shown in a longitudinal aberration diagram, in which the origin is the intersection point between the optical axis of the lens and the surface of a workpiece, the horizontal axis is the optical axis with the direction in which light travels on the positive side, and the vertical axis is normalized pupil coordinates, is larger than the area on the negative side, and the optical constants of the lens are determined so that this first requirement is further satisfied.

8. 7. A light irradiation device according to claim 6, wherein the second requirement is that the sum of the slopes of the aberration curve at each point spaced apart by an infinitesimal distance is positive, and the optical constants of the lens are determined so that the second requirement is further satisfied.

Images