Light irradiation device and light irradiation method

Abstract

A plurality of light source bodies (2) arranged along a predetermined direction, and a lens (3) that has no curvature in the predetermined direction and has curvature in a plane perpendicular to the predetermined direction, and collects light of a component emitted from the light source bodies (2) and traveling along the plane perpendicular to the predetermined direction, and when viewed from the predetermined direction, the optical constant of the lens (3) is determined such that the area of ​​the positive side of the aberration curve, which is represented by a vertical aberration diagram with the origin point being the intersection point between the optical axis (C) of the lens (3) and the surface of the work, the optical axis (C) with the direction of light travel as the positive side, and the vertical axis being the normalized pupil coordinate, is larger than the area of ​​the negative side.

Description

Technology Field

[0001] The present invention relates to a light injection device used for surface inspection devices or exposure devices, and in particular to a light irradiation device that irradiates a line-shaped or band-shaped light, also called line light, onto a workpiece. Background Technology

[0002] As a light irradiation device of this type, for example as shown in Patent Document 1, a so-called line light irradiation type is known, which emits light from a plurality of LEDs in series through a rod lens and irradiates a line or band-shaped light onto a workpiece.

[0003] Conventionally, when using such a light irradiation device, it is recommended that the workpiece be installed at the position where the light emitted from the LED is most concentrated when viewed from the serial direction of the LED (hereinafter also referred to as the Z direction).

[0004] Conversely, if the isolation distance between the light irradiation device and the workpiece—that is, the recommended installation distance—is predetermined, the optical constants (such as curvature) of the lens are determined so that the LED light is most concentrated at that distance.

[0005] However, if the workpiece is installed at this recommended installation distance, the radiant intensity on the workpiece becomes the highest, so, for example in the field of surface inspection, the shutter speed of the camera when capturing the workpiece can be increased, or the speed can be increased without stopping the transport of the workpiece, thereby shortening the inspection lead time.

[0006] However, the inventors, through careful examination, discovered for the first time that the highest radiation intensity in a line light irradiation type light irradiation device is not the conventionally recommended installation distance, and thus completed the present invention. Prior art literature

[0007] Japanese Patent Publication No. 2017-150875 The problem to be solved

[0008] The present invention is based on a line light irradiation type light irradiation device that overturns conventional technical common sense, and is designed to enable the light irradiation device to fully demonstrate its performance. means of solving the problem

[0009] That is, the light irradiation device according to the present invention is as follows.

[0010] [1]

[0011] By irradiating a workpiece with a linear or band-shaped light extending along a predetermined direction,

[0012] A plurality of light sources arranged along the above-mentioned predetermined direction, and

[0013] A lens having no curvature in the aforementioned predetermined direction and having curvature in a plane perpendicular to the aforementioned predetermined direction, and concentrating light of a component emitted from the light source and traveling along the said perpendicular plane,

[0014] A light irradiation device characterized by having a first requirement that, when viewed from the above-mentioned predetermined direction, the area on the positive side of the aberration curve represented by a vertical aberration diagram in which the origin is the intersection point between the optical axis of the lens and the surface of the workpiece, the horizontal axis is the optical axis with the direction of light propagation as the positive side, and the vertical axis is the normalized pupil coordinate, is larger than the area on the negative side, and the optical constant of the lens is determined so that this first requirement is satisfied.

[0015] In this way, it becomes possible to maximize the radiant illuminance on the work surface. Furthermore, since deviations from the first requirement can be excluded, optical design becomes easier. Additionally, the optical constants of a lens include at least one of the following: lens curvature, refractive index, thickness, number of lenses, mounting position, front and back, aspheric coefficient, and conic constant.

[0016] [2]

[0017] A light irradiation device described in [1], wherein the second requirement is that the sum of the slopes at each point separated by a small distance in the above aberration curve is positive, and the optical constant of the lens is determined so as to further satisfy this second requirement.

[0018] With such a configuration, the degree of reduction in radiant illuminance can be set to be nearly symmetrical at the distance where radiant illuminance is maximum, i.e., the recommended installation distance. Therefore, even if the separation distance between the workpiece and the light irradiation device deviates from the recommended installation distance due to placement errors or the like, it is possible to prevent a rapid decrease in radiant illuminance.

[0019] [3]

[0020] A light irradiation device described in either [1] or [2], characterized in that the optical constant of the lens is set so that the position of light collection from the LED changes continuously or stepwise along the lens optical axis as it moves from the center of the lens toward the outer edge.

[0021] With this configuration, the degree of variation in radiant intensity accompanying changes in the isolation distance between the workpiece and the light irradiation device can be minimized, thereby securing a usable range of isolation distances while ensuring a constant radiant intensity around the recommended isolation distance. Furthermore, when the recommended isolation distance is configured to be switchable while ensuring a constant radiant intensity, it becomes possible to further reduce the number of switching stages.

[0022] In other words, it is possible to ensure the necessary radiation intensity on the workpiece while simplifying the configuration.

[0023] In addition, the focusing position is the position where the luminous flux diameter is smallest, and the luminous flux diameter is a certain ratio (e.g., 1 / e) to the maximum radiant illuminance within a cross-section perpendicular to the optical axis. 2It is the diameter at which radiant intensity greater than ) is obtained.

[0024] [4]

[0025] A light irradiation device described in [3], further having a distance variable structure that allows the distance between the lens and the LED to be changed stepwise.

[0026] With this, the recommended isolation distance can be switched with a simple structure.

[0027] [5]

[0028] A light irradiation device described in [3] or [4], characterized in that the optical constant of the lens is set so that the more light passes through the center of the lens, the closer the gathering position is to the lens.

[0029] This configuration can be realized, for example, by setting the curvature of the center of the lens to be greater than the curvature of the outer region. As a result, the edge thickness can be set thicker and the center thickness thinner, making it easier to manufacture the lens. Specifically, the thickness deviation ratio (center thickness / edge thickness) is reduced, which not only improves injection moldability but also makes it possible to reduce the volume, thereby suppressing manufacturing costs.

[0030] [6]

[0031] A light irradiation device described in any one of [3] to [5], wherein the above lens is divided into multiple zones between the center and the outer edge, and the curvature in each zone is different.

[0032] With this, performance and size that cannot be achieved with a continuously smooth lens surface can be realized, thereby increasing the degree of design freedom. Here, the curvature in each zone refers, for example, to the curvature at the center of each zone.

[0033] [7]

[0034] A light irradiation device described in [6], wherein the curvature of the lens surface at which the light beam closest to parallel to the optical axis of the lens is incident is different in each zone.

[0035] In this way, even if a step difference occurs at the boundary of adjacent zones, light loss or the occurrence of stray light caused by such step difference can be suppressed as much as possible. In addition, the viewing angle of the light source (collimation half-angle) seen from one point on the lens surface defining each zone can be set to be as small as possible, and as a result, there is no need to care for light incident at an angle, and it is less susceptible to the effects of manufacturing imbalance, allowing multiple light gathering positions to be set in the direction of the lens optical axis with greater precision.

[0036] In addition, the present invention relates to a light irradiation method using a light irradiation device comprising a plurality of light sources arranged along a predetermined direction, a lens having no curvature in the predetermined direction and curvature in a plane perpendicular to the predetermined direction, and concentrating light of a component emitted from the light sources and propagating along the perpendicular plane, wherein the light irradiates a workpiece with a linear or band-shaped light extending along the predetermined direction.

[0037] It may also be a light irradiation method characterized by determining the recommended installation distance of the workpiece such that, when viewed from the above-mentioned predetermined direction, the origin is the intersection point between the optical axis of the lens and the surface of the workpiece, the horizontal axis is the optical axis with the direction of light propagation as the positive side, and the vertical axis is the normalized pupil coordinate, so that the area on the positive side of the aberration curve is larger than the area on the negative side. Effects of the invention

[0038] According to the present invention configured in this manner, the radiant intensity on the work surface can be set to be the highest. Brief explanation of the drawing

[0039] FIG. 1 is a perspective view showing the entire light irradiation device in one embodiment of the present invention. FIG. 2 is a schematic diagram showing light traveling in a first XY plane including one LED in one embodiment of the present invention. Figure 3 is a schematic diagram showing the conventional recommended installation distance. Figure 4 is a view from the Y direction to qualitatively explain the light-gathering position of each LED in the first XY plane. Figure 5 is a graph showing the radiant intensity by one LED, the radiant intensity by another LED, and the combined radiant intensity therefrom at each isolation distance, as well as qualitatively showing the conventional recommended installation distance. FIG. 6 is a vertical aberration diagram showing the aberration curve in the above-mentioned embodiment. FIG. 7 is a qualitative graph showing the radiant intensity by one LED, the radiant intensity by another LED, and the combined radiant intensity therefrom at each isolation distance in the above-mentioned embodiment, as well as the recommended installation distance. FIG. 8 is a schematic diagram showing the curvature of a lens in the above-mentioned embodiment. FIG. 9 is a schematic diagram showing the light collection position of light passing through each zone of the lens in the above embodiment. FIG. 10 is a graph that qualitatively shows a plurality of switchable recommended installation distances in the above-mentioned embodiment, as well as changes in radiant intensity associated with the installation distance of the work, a maximum radiant intensity curve, and a minimum guaranteed radiant intensity curve. FIG. 11 is a schematic diagram showing the configuration of a lens in another embodiment of the present invention. FIG. 12 is a graph that qualitatively shows the change in radiant irradiance associated with the installation distance of the work, the maximum radiant irradiance curve, and the minimum guaranteed radiant irradiance curve when using a lens with no zone division and small aberrations. Specific details for implementing the invention

[0040] One embodiment of the present invention will be described below with reference to the drawings.

[0041] The light irradiation device (100) according to the present embodiment is a line light irradiation type that irradiates a straight line or straight strip of light (hereinafter also referred to as line light) onto a workpiece, and is referred to as a line lighting device or a bar lighting device, etc.

[0042] As shown in FIGS. 1 and 2, this light irradiation device (100) has a substrate (1), an LED (2) which is a light source, a lens (3), a distance variable structure (5) which can change the distance between the lens (3) and the LED (2) in steps, and a housing (4) that accommodates these.

[0043] Explain each part.

[0044] The substrate (1) forms a straight strip shape. As this substrate (1), a wiring board made of metal or resin is used.

[0045] The LED (2) is, for example, of a surface-mount type, and a plurality of LEDs (2) are mounted so as to be arranged in a straight line at regular intervals along the length direction of the substrate (1). Although these LEDs (2) are arranged in a single row here, they may be arranged in multiple rows, and the spacing may be irregular rather than regular.

[0046] As shown in FIG. 1 and FIG. 2, the lens (3) is of the cylindrical type, having no curvature in the cross-section cut along the elongation direction and curvature in the cross-section perpendicular to the elongation direction, and is positioned on the LED mounting surface side of the substrate (1) such that the elongation direction coincides with the length direction of the substrate (1) and, when viewed from the length direction, the lens optical axis (C) passes through the LED (2).

[0047] In addition, although a two-group lens is shown here, it may be a single group or three or more groups. Also, it may be a lens in which both surfaces have curvature in the vertical cross-section above. Also, it may be a spherical type or an aspherical type.

[0048] In the following, for convenience of explanation, the longitudinal direction of the substrate (1) or the elongation direction of the lens (3) corresponding thereto is referred to as the Z direction, the direction of the lens optical axis when viewed from the Z direction is referred to as the X direction, and the direction perpendicular to the X direction and the Z direction is referred to as the Y direction. Additionally, FIG. 2 shows light traveling along a plane perpendicular to the Z direction (hereinafter also referred to as the first XY plane) including any one LED (2).

[0049] The above distance variable structure (5) is composed of a plurality of grooves extending in the Z direction (long direction) provided on the side walls of the housing (5), for example, as shown in FIG. 2. By inserting a lens (3) into any of these grooves, the distance between the LED (2) and the lens (3) can be changed in multiple stages. In addition, although it is configured to change the X-direction position of the first stage lens (31) here, it may also change the position of the second stage lens (32) or change the positions of all of them. Furthermore, it does not matter if the position of the substrate (1) is changed.

[0050] The above housing (4) is shaped like a rectangular prism or a rectangular parallelepiped that maintains the above substrate (1) and the lens (3) in the aforementioned relative positional relationship. An opening (41) is provided on the surface of the housing (4) facing the lens (3), and the line light is emitted from the opening (41).

[0051] In a light irradiation device (100) of such a configuration, a recommended installation distance is determined, which is the position where a work is to be placed relative to the light irradiation device (100) or the position where the light irradiation device (100) is to be placed relative to the work.

[0052] So, first, I will explain the conventional recommended installation distance.

[0053] Conventionally, as shown in FIG. 3, attention is focused on light traveling along the first XY plane, in other words, light that does not contain a Z-direction component emitted from a single LED (here, denoted as the first LED), and the distance to the focusing position, which is the position where the diameter of the light beam of this light is smallest, is set as the recommended installation distance. Then, the relative arrangement relationship between the workpiece and the light irradiation device is set so that this recommended installation distance is achieved, or the optical constants of the lens are set so that the light is focused at a predetermined recommended installation distance. In addition, for ease of understanding, the light rays in the case where there are no aberrations are described in the same figure.

[0054] However, in reality, since light including a Z-direction component is also emitted from the LED, light from other LEDs also enters this first XY plane. For example, as shown in FIG. 4, the light concentration position in the first XY plane of the light from the LEDs on both sides of the first LED (the second LED or the third LED) is closer to the light irradiation device than the recommended installation distance.

[0055] And, FIG. 5 is a graph showing the radiant intensity for each isolation distance between the light irradiation device and the work surface in this first XY plane, taking into account other LEDs.

[0056] Conventionally, the position where the radiant intensity is maximized was determined by focusing only on the first LED, but from this drawing, it can be seen that the distance where the combined radiant intensity including the light from other LEDs is maximized is shorter than the above recommended installation distance and is on the side of the light irradiation device.

[0057] Thus, in a line light irradiation type light irradiation device, the position where the combined radiation intensity is maximum is closer to the light irradiation device than the conventional recommended installation distance, which was discovered for the first time by the inventors of the present invention. And, in accordance with this finding, and also taking into account that there is aberration in reality as shown in FIG. 2, the light irradiation device (100) in this embodiment is configured.

[0058] Specifically, it is as follows.

[0059] That is, as shown in FIG. 6, a longitudinal aberration diagram is considered with the origin as the intersection point between the lens optical axis (C) in the first XY plane and the work surface, the horizontal axis as the lens optical axis (C) (however, the direction in which light travels is positive), and the vertical axis as the normalized pupil coordinates in the first XY plane. In this longitudinal aberration diagram, the first requirement is that the area on the positive side of the aberration curve of light emitted from one LED (2) in the first XY plane is larger than the area on the negative side, and the optical constant of the lens (3) (here, at least the curvature is included, but it is acceptable to use an optical constant excluding the curvature) or the recommended installation distance is determined to satisfy this first requirement.

[0060] In addition, the “pupil” here refers to the image of an aperture (opening (41) in FIG. 2) that defines the light emission diameter when viewed from the work side.

[0061] In addition, the “area on the positive side” of the aberration curve here refers to the area of ​​the region enclosed by the vertical axis passing through the origin and the aberration curve on the positive side of this vertical axis in the above-mentioned vertical aberration diagram, and is the area of ​​“A+” in Fig. 6. In addition, the “area on the negative side” refers to the area of ​​the region enclosed by the vertical axis passing through the origin and the aberration curve on the negative side of this vertical axis, and is the area of ​​“A-” in the same diagram.

[0062] If it is (a) of the same drawing, 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. If it is (b) of the same drawing, the area of ​​“A+” is larger than the area of ​​“A-”, so this first requirement is also satisfied.

[0063] In addition, by determining the recommended installation distance to satisfy at least the first requirement above, the composite radiant intensity on the work surface can be maximized.

[0064] On the other hand, as shown in FIG. 5, the inventors have discovered for the first time that in a conventional configuration, the (synthetic) irradiance on the surface of the workpiece decreases rapidly in the direction away from the light irradiation device, centered on the maximum irradiance distance.

[0065] Therefore, in this embodiment, a second requirement is that the sum of the slope values ​​at each point separated by a small distance in the above aberration curve is positive, and the optical constant of the lens (here, at least including curvature, but it may be an optical constant excluding curvature) is determined to satisfy this second requirement.

[0066] For example, Figure 6 (a) satisfies the second requirement above because the slope is positive across all points of the aberration curve. Also, Figure 6 (b) satisfies the second requirement above because although there are parts of the aberration curve where the slope is negative, the slope is positive at other points, and it is clear that the sum of them is positive.

[0067] By this, as shown in FIG. 7, the degree of decrease in radiant illumination before and after the maximum radiant illumination distance can be made nearly symmetrical, and a rapid decrease in radiant illumination can be prevented in either before or after the maximum radiant illumination distance. As a result, unpredictable decrease in radiant illumination caused by, for example, errors in the placement of the work or the light irradiation device (100) can be prevented.

[0068] In addition, in this embodiment, as shown in FIG. 8, the lens (3) is divided into a plurality of zones (Z1 to Z3) extending from the center to the outer edge, and the optical constant (here, curvature) of the lens (3) in each zone (Z1 to Z3) is different, and as shown in FIG. 9, the light gathering position (F1 to F3) of the light passing through each zone (Z1 to Z3) is configured to change stepwise along the lens optical axis (C).

[0069] Here, the curvature is set to be greater the closer the zone is to the center, and the light passing through the zone closer to the center is configured so that its gathering position is closer to the lens (3). Also, in this drawing, for convenience of explanation, the lens (3) is shown as a single unit.

[0070] In addition, in this lens (3), the part that has different curvature in each zone is the lens surface (3a) where the light beam closest to parallel with respect to the lens optical axis (C) is incident (hereinafter also referred to as the different curvature lens surface (3a) to distinguish it from other lens surfaces). As shown in FIGS. 2 and FIGS. 9, the different curvature lens surface (3a) is the surface closest to the work. Also, in the case of a multi-lens system having, for example, a concave lens, the different curvature lens surface cannot be said to be the surface closest to the work.

[0071] In such a configuration, even if the isolation distance between the work and the light irradiation device (100) is arbitrarily changed, if the minimum guaranteed radiant illuminance at any isolation distance is secured by setting it to one of the multiple recommended isolation distances, as shown in FIG. 10, the degree of reduction in radiant illuminance before and after the recommended installation distance is low, and the peak angle of the radiant illuminance shown by the solid line becomes larger than when using a lens with no zone division and small aberrations as shown in FIG. 12, so the number of switching stages for the recommended isolation distance can be reduced. In FIG. 10, for example, the recommended isolation distance can be reduced to three stages. In addition, in the same figure, a certain percentage (for example, 70%) of the maximum radiant illuminance is set as the minimum guaranteed radiant illuminance.

[0072] Therefore, by reducing the number of switching stages of the recommended isolation distance, the configuration can be simplified, while ensuring the necessary radiant intensity on the workpiece over a wide range of distances from the light irradiation device.

[0073] Furthermore, the present invention is not limited to the above embodiments.

[0074] For example, either the first requirement or the second requirement may be satisfied.

[0075] In the above embodiment, a plurality of zones were set in the lens and the curvature in each zone was changed stepwise, but the light gathering position may be changed by changing other optical constants related to the lens, such as the refractive index of each zone.

[0076] 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.

[0077] The curvature of the lens may be allowed to change continuously.

[0078] To change the recommended isolation distance to multiple stages, multiple lenses with different curvatures may be prepared and configured to be interchangeable.

[0079] It is fine to configure it so that the recommended isolation distance can be changed continuously.

[0080] It is not limited to LEDs; other light sources such as semiconductor lasers can also be used.

[0081] Furthermore, the present invention is not limited to the above embodiments and various modifications are possible within the scope without departing from the spirit thereof. Industrial applicability

[0082] According to the present invention, in a line light irradiation type light injection device, the radiant intensity on the surface of the workpiece can be maximized. Explanation of the symbols

[0083] 100… light irradiation device 2… LED (light source) 3… lens A+… Area on the positive side A-… Area on the negative side

Claims

Claim 1 A light irradiation device for irradiating a workpiece with a linear or band-shaped light extending along a predetermined direction, comprising a plurality of light source bodies arranged along the predetermined direction, and a lens having no curvature in the predetermined direction and curvature in a plane perpendicular to the predetermined direction, and concentrating a component of light emitted from the light source bodies and propagating along the plane perpendicular to the predetermined direction, wherein, when viewed from the predetermined direction, the origin is the intersection point between the optical axis of the lens and the surface of the workpiece, the optical axis with the direction of light propagation as the positive side, and the vertical axis is a normalized pupil coordinate, wherein the area of ​​the positive side of the aberration curve is greater than the area of ​​the negative side, as a first requirement, and the optical constant of the lens is determined so as to satisfy this first requirement. Claim 2 A light irradiation device according to claim 1, wherein, in the aberration curve, the sum of the slopes at each point separated by a small distance is positive as a second requirement, and the optical constant of the lens is determined so as to further satisfy this second requirement. Claim 3 A light irradiation method using a light irradiation device comprising a plurality of light sources arranged along a predetermined direction, a lens having no curvature in the predetermined direction and curvature in a plane perpendicular to the predetermined direction, and concentrating a component of light emitted from the light sources and propagating along the plane perpendicular to the predetermined direction, wherein the light irradiation device irradiates a workpiece with a line-shaped or band-shaped light extending along the predetermined direction, wherein, when viewed from the predetermined direction, the area of ​​the positive side of an aberration curve represented by a vertical aberration diagram in which the origin is the intersection point between the optical axis of the lens and the surface of the workpiece, the optical axis with the direction of light propagation as the positive side, and the vertical axis as normalized pupil coordinates is a first requirement that the area of ​​the positive side of the aberration curve is greater than the area of ​​the negative side, and a recommended installation distance between the workpiece and the light source is determined so that the first requirement is satisfied.

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