Interference fringe inspection device

Abstract

The invention provides an interference fringe inspection device which can contribute to miniaturization (especially thinning), output stability, inspection precision improvement and the like. An interference fringe inspection device is provided with a light emission device (100) for emitting inspection light, the light emission device (100) being provided with a flat plate-shaped light guide plate (2) having an equal thickness, and a plurality of laser light sources (3) arranged side by side along the side peripheral surface (2a) of the light guide plate (2). The light emitting device (100) is configured such that the laser light emitted from the laser light sources (3) and guided into the light guide plate (2) from the side peripheral surface (2a) of the light guide plate (2) is diffused and reflected by a plurality of minute light diffusion and reflection parts (6) formed on one plate surface (2b) of the light guide plate (2), and is emitted from the other plate surface (2c) of the light guide plate (2). The direction in which the pointing angle of each laser beam is wide is configured so as to coincide with or be within a prescribed range of the thickness direction of the light guide plate (2).

Description

Technical Field

[0001] The present invention relates to an interference fringe inspection apparatus that irradiates a surface of an inspection object with monochromatic light to generate interference fringes and inspects using the interference fringes. Background Art

[0002] As shown in Patent Document 1, a conventional interference fringe inspection apparatus is known that irradiates an inspection object surface that is smooth with inspection light from a light emitting surface of a certain size to generate interference fringes, and detects unevenness and deformation of the inspection object surface based on disorder of the interference fringes.

[0003] Since this inspection light requires high monochromaticity of light, in such a conventional interference fringe inspection apparatus, for example, by passing multi-wavelength light emitted from a light source such as a mercury lamp through a band-pass filter or the like, inspection light with high monochromaticity is generated.

[0004] However, in the above configuration, since most of the light emitted from the light source is cut off, the light utilization efficiency is poor. Therefore, if the output of the light source is increased to ensure the necessary output, corresponding heat dissipation performance is required, which causes problems such as enlargement of the apparatus or increase in price.

[0005] That is, in the case of a configuration in which an LED with relatively high monochromaticity is used as a light source and a part of the unnecessary wavelength light is cut off by a band-pass filter, although the light utilization efficiency is indeed improved compared to the above multi-wavelength light source, since the peak wavelength of the LED shifts due to temperature, the amount of light per unit time passing through the band-pass filter varies according to temperature, and there is a possibility of significant output fluctuations.

[0006] On the other hand, if a laser is used as the light source, the light source itself becomes ideal monochromatic light for interference fringe inspection, so there is no need to cut off unnecessary light with a band-pass filter or the like. However, due to the influence of speckle, bright spots other than interference fringes are generated on the inspection object surface, which causes a problem of deterioration in inspection accuracy. In addition, since the divergence angle of the laser is more likely to be narrower than that of the above other light sources, it is easy to generate uneven irradiance, which also has an adverse effect on the inspection accuracy. Prior Art Documents Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-16552 Summary of the Invention Problems to be Solved by the Invention

[0008] Here, the present invention is proposed to solve the above problems at once, and its main object is to provide an interference fringe inspection apparatus that can contribute to miniaturization (especially thinning), output stability, improvement in inspection accuracy, and the like. Technical means for solving the problem

[0009] That is, the interference fringe inspection device of the present invention is as follows. [1] An interference fringe inspection device, which is provided with a light emitting device for emitting inspection light. The interference fringe inspection device is characterized in that the light emitting device includes a light guide plate in the shape of an equal thickness flat plate and a plurality of laser light sources arranged along the side circumferential surface of the light guide plate. The light emitting device is configured such that the laser light emitted from these laser light sources and guided into the light guide plate from the side circumferential surface thereof is diffusely reflected by a plurality of minute light diffusion reflection portions formed on one plate surface of the light guide plate, and is emitted from the other plate surface of the light guide plate. The direction of the angular width of the directivity of each laser light is configured to be the same as or within a specified range of the thickness direction of the light guide plate.

[0011] The above configuration was first discovered by the present inventor through in-depth research. That is, in the past, when light was introduced from the side circumferential surface of the light guide plate, the light was diffusely reflected by the light diffusion reflection portion and emitted from the plate surface, the direction of the angular width of the introduced light was set to be parallel to the plate surface of the light guide plate, and it was set such that the light diffused as much as possible within the light guide plate in a top view. This is because it was considered that the light would irradiate more light diffusion reflection portions, and the area where the light overlapped with the light from adjacent light sources would also become larger, enabling uniform surface light emission.

[0012] However, the present inventor first discovered through simulation, experiments, etc. that the opposite phenomenon occurs when the light source is a laser, and completed an interference fringe inspection device with improved uniformity of irradiance and improved inspection accuracy.

[0013] In addition, according to the above configuration, even if the mounting pitch of the semiconductor lasers is increased, the luminance uniformity of the light emitting surface is high. For example, even when formed in multiple colors, the uniformity of irradiance when each color is lit is good, and color unevenness when multiple colors are lit simultaneously can be reduced.

[0014] Furthermore, since the laser light is emitted through a plurality of light diffusion reflection portions, speckle noise can be reduced and can be made as close to 0 as possible. The reason is that the speckle noise decreases in inverse proportion to the square root of the number of light sources, but by passing through the light diffusion reflection portion, a state where there are a plurality of light sources can be approximated. This also contributes to the improvement of inspection accuracy.

[0015] In addition, if a laser is used as the light source, due to the monochromaticity of the emitted light, a filter is not required. Therefore, compared with other light sources, the utilization efficiency of light is high, and energy loss can be suppressed. Thus, for example, simplification of the structure and miniaturization of the device can be achieved by reducing the heat dissipation function and the number of components. Furthermore, since a filter is not used, the output variation depends only on the laser light source. By using a semiconductor laser or the like as the laser light source, sufficient stability of the output can be ensured.

[0016] In addition, since the basic configuration is to introduce the laser from the side peripheral surface of the light guide plate and emit it from the plate surface, it also contributes to the thinning of the device. [2] In the interference fringe inspection device according to [1], between the side peripheral surface of the light guide plate and the laser light source, a spacer member having a through hole through which the laser passes is disposed, and a reflecting surface is formed on the surface of the spacer member facing the side peripheral plate of the light guide plate.

[0018] If such a structure is adopted, even if the laser introduced into the light guide plate penetrates from the side peripheral surface of the light guide plate, it can be reflected by the reflecting surface and the laser can be introduced again from the side peripheral surface of the light guide plate. Therefore, light loss can be prevented as much as possible, and the utilization efficiency of the laser can be improved. [3] The interference fringe inspection device according to [1] or [2] further includes a light transmission diffusion member that is provided on the other plate surface side of the light guide plate and diffuses the transmitted light, and the interference fringe inspection device is configured such that the light emitted from the other plate surface of the light guide plate and transmitted through the light transmission diffusion member is emitted to the outside as inspection light.

[0020] If such a structure is adopted, by passing through the light diffusion reflection portion and the diffusion transmission member, a state where there are countless light sources can be approximated, and the speckle noise can be substantially reduced to the level of 0. Effects of the Invention

[0021] According to the present invention configured as described above, miniaturization, output stability, low cost, improvement of inspection accuracy, etc. can be achieved in a device or the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is an overall perspective view of a light emitting device according to an embodiment of the present invention. Figure 2 is Figure 1 a cross-sectional view taken along line A - A in Figure 3 is Figure 2 an enlarged view of part B in Figure 4 is a partial cross-sectional perspective view of the light emitting device of this embodiment. Figure 5 It is a top view of the light guide plate in this embodiment. Figure 6 It is a schematic diagram showing the laser traveling inside the light guide plate as observed from the Z direction in this embodiment. Figure 7 It is a schematic diagram showing the laser traveling inside the light guide plate as observed from the Y direction in this embodiment. Figure 8 It is a cross-sectional view of the laser cut by a plane perpendicular to the traveling axis in this embodiment. Figure 9 It is an irradiance distribution diagram of the inspection light on the surface of the object to be inspected when the direction in which the divergence angle of the laser is narrow is parallel to the plate surface of the light guide plate in this embodiment. Figure 10 It is Figure 9 a comparative example, and it is an irradiance distribution diagram of the inspection light on the surface of the object to be inspected when the direction in which the divergence angle of the laser is wide is parallel to the plate surface of the light guide plate. Detailed Embodiment

[0023] An embodiment of the interference fringe inspection apparatus will be described below with reference to the drawings.

[0024] The interference fringe inspection apparatus of this embodiment is for irradiating a single-wavelength inspection light onto an object to be inspected such as a transparent film or a transparent surface layer, and inspecting the surface deformation, thickness, etc. of the object to be inspected through the interference fringes generated by the irradiation. The interference fringe inspection apparatus further includes: a surface light-emitting type light-emitting device that emits the inspection light, and a imaging device (not shown) that images the object to be inspected.

[0025] In addition, when observing the interference fringes with the naked eye without using the imaging device, since the interference fringe inspection apparatus is composed only of the light-emitting device, the interference fringe inspection apparatus is equivalent to the light-emitting device.

[0026] Hereinafter, the light-emitting device 100 used in this interference fringe inspection apparatus will be described in detail.

[0027] As Figure 1 , Figure 2 shown, the light-emitting device 100 has a flat plate shape and includes: a frame 1 having a light-emitting surface S formed on one plate surface, a light guide plate 2 housed in the frame 1, and semiconductor lasers 3 as a plurality of laser light sources disposed at positions facing the side peripheral surface 2a of the light guide plate 2.

[0028] As Figure 1 , Figure 2As shown, the housing 1 includes: a bottom plate 11, which is rectangular (square in this case) when viewed from above; four side peripheral plates 12, which stand up from the respective side portions of the bottom plate 11; and a top plate 13, which is disposed opposite to the bottom plate 11 and has a rectangular (square in this case) opening 13a formed at the center to serve as the light emitting surface S. In addition, when specifying the following directions, as shown in this figure, there are the following cases: the thickness direction of the housing 1 is referred to as the Z direction, one side direction is referred to as the X direction, and the direction of the adjacent side orthogonal to this side is referred to as the Y direction.

[0029] The peripheral portion of the bottom plate 11 is a thin wall portion 11a, and the central portion is a thick wall portion 11b that protrudes toward the light emitting surface side. The top view shape of the thick wall portion 11b is the same as the top view shape of the light guide plate 2 described later.

[0030] As Figure 3 shown, the semiconductor laser 3 has a cap-shaped CAN package composed of a small-diameter cylindrical portion and a large-diameter cylindrical portion, and a laser element (not shown) housed in the CAN package. Laser light is emitted from a light exit port 3a provided on the top surface of the small-diameter cylindrical portion.

[0031] In this embodiment, a plurality of semiconductor lasers 3 are mounted on the surface of an elongated strip-shaped mounting substrate 4 at equal intervals with a heat sink 10 interposed therebetween. The dimension in the length direction of the mounting substrate 4 is substantially the same as the dimension of one side of the light guide plate 2 described later.

[0032] The light guide plate 2 is, for example, a resin-made (PMMA-made in this case) transparent plate having a constant thickness and a rectangular (square in this case) shape. And, as Figure 5 shown, on one of the mutually parallel plate surfaces, i.e., the plate surface 2b, many minute light diffusion reflection portions 6 are formed, and the other plate surface 2c is formed as a smooth mirror surface. In this embodiment, these light diffusion reflection portions 6 are partially concave spherical shapes that penetrate one plate surface 2b of the light guide plate 2, and these light diffusion reflection portions 6 are regularly arranged at square lattice points. In addition, as the light diffusion reflection portions 6, minute dots that diffusely reflect light may also be coated on the one plate surface 2b to form them.

[0033] The light guide plate 2 configured as described above is placed such that the plate surface 2b on which the light diffusion reflection portions 6 are formed is close to or joined to the thick wall portion 11b of the housing bottom plate 11. In addition, the mounting substrates 4 are respectively disposed outside a pair of opposite side peripheral surfaces 2a of the light guide plate 2, and the light exit ports 3a of the semiconductor lasers 3 mounted on these respective mounting substrates 4 are configured to face the side peripheral surfaces 2a of the light guide plate 2. In addition, the dimension in the length direction of the mounting substrate 4 is substantially the same as the dimension of one side of the light guide plate 2.

[0034] In addition, in the present embodiment, a spacer member 7 for maintaining a constant distance between the semiconductor laser 3 and the side peripheral surface 2a of the light guide plate 2 is provided therebetween. The spacer member 7 is configured in an elongated plate shape, mounted on the housing 1, and covers the entire side peripheral surface 2a of the light guide plate. A through hole 7a penetrating in the thickness direction thereof is provided in the spacer member 7, and the semiconductor laser 3 is inserted into the through hole 7a. Further, by contacting the stepped portion provided in the through hole 7a with the large diameter portion of the semiconductor laser 3, and contacting the inner surface of the spacer member with the side peripheral surface 2a of the light guide plate 2 via the thin-walled reflector 9, the distance between the semiconductor laser 3 and the side peripheral surface 2a of the light guide plate 2 is maintained constant as described above. In addition, it is configured that a through hole 9a is provided in the reflector 9 at a position continuous with the through hole 7a of the spacer member 7, and the laser is introduced into the light guide plate 2 through the through hole 9a.

[0035] Furthermore, in the present embodiment, a light-transmitting diffusion member 8 formed in an isopachous flat plate shape is disposed at a predetermined distance from the other surface of the light guide plate 2 and is arranged directly above it.

[0036] Next, the light-emitting structure of the light-emitting device 100 configured as described above will be described.

[0037] The laser beam emitted from the semiconductor laser 3 is diffused at a diffusion angle (as shown in Figure 6 , Figure 7 the diffusion angle when viewed from the Z direction is set as α, and the diffusion angle when viewed from the Y direction is set as β. Here, α < β) specified in its specifications and travels in the X-axis direction, and is respectively introduced into the light guide plate 2 from the opposite side peripheral surfaces 2a thereof.

[0038] Then, it is repeatedly totally reflected between the opposite plate surfaces 2b and 2c of the light guide plate 2 and travels inside. During this travel, it hits the light diffusion reflection portion 6, where it is diffusely reflected and exits from the other plate surface 2c of the light guide plate 2. That is, the other plate surface 2c of the light guide plate 2 becomes the light-emitting surface. In addition, although light also slightly leaks from one plate surface 2b, the leaked light is reflected by the surface of the thick wall portion 11b of the bottom plate 11 that is close to or joined to the one plate surface 2b, and is introduced into the light guide plate 2 again, and still exits to the outside of the light guide plate 2 from the other plate surface 2c. The laser beam introduced into the light guide plate 2 and reaching the opposite side peripheral surface 2a is also reflected by the inner surface of the reflector 9 joined to the side peripheral surface 2a of the light guide plate 2, and is introduced into the light guide plate 2 again, and finally exits from the other plate surface 2c.

[0039] In addition, in order to effectively reflect, the surface of the thick wall portion 11b of the bottom plate 11 and the inner surface of the reflector 9 are formed into light-reflecting surfaces for specular reflection or diffuse reflection of light by mirror processing, coating with a light-reflecting agent, etc.

[0040] As described above, the light emitted from one surface of the light guide plate 2 passes through the light transmissive diffusion member 8 and is emitted from the light emitting surface S as inspection light toward the inspection object.

[0041] However, in the present embodiment, as Figures 6 to 8 shown, the posture of each semiconductor laser 3 is determined such that the direction of the wide divergence angle of the laser light emitted from each semiconductor laser 3 coincides with the thickness direction of the light guide plate 2, in other words, the direction of the wide divergence angle of the laser light is perpendicular to the arrangement direction of the semiconductor lasers 3. Further, Figure 8 is a cross section cut by a plane perpendicular to the traveling axis of the laser light.

[0042] Thereby, it is possible to reduce the irradiance unevenness as much as possible and improve the inspection accuracy.

[0043] This has been first discovered by the present inventors through intensive research. Generally, in the case where light is introduced from the side peripheral surface 2a of the light guide plate 2, diffused and reflected by the light diffusion reflection portion 6, and emitted from the plate surface, the direction of the wide divergence angle of the introduced light is made parallel to the plate surface of the light guide plate 2, and in a plan view, the light is diffused as much as possible within the light guide plate 2. This is because it is considered that since the light irradiates more light diffusion reflection portions 6 and the region where the light overlaps with the light from adjacent light sources also becomes larger, uniform surface light emission can be achieved.

[0044] However, the present inventors have first discovered through simulation and experiments that the opposite phenomenon occurs in the case where the light source is a laser.

[0045] The simulation results are as Figure 9 and Figure 10 shown.

[0046] This Figure 9 and Figure 10 represent the irradiance distribution of the inspection light on a virtual surface that is at a predetermined distance from the light emitting surface, that is, on the surface of the inspection object. From this, it can be seen that the uniformity of the irradiance is significantly improved in the case where the direction of the narrow divergence angle of the laser light is parallel to the plate surface of the light guide plate 2 ( Figure 10 ) compared to the case where the direction of the wide divergence angle of the laser light is parallel to the plate surface of the light guide plate 2 ( Figure 9 ).

[0047] In addition, it can also be confirmed that the same effect can be obtained even if the direction of the narrow divergence angle of the laser light is inclined to the plate surface of the light guide plate 2 by 30 degrees.

[0048] As a result, even if the mounting pitch of the semiconductor lasers 3 is increased, the luminance uniformity of the light emitting surface is high. For example, even in the case of multi-color illumination, the uniformity of the irradiance when lighting up in various colors is good, and the color unevenness when lighting up multiple colors simultaneously can be reduced.

[0049] Furthermore, since the laser light emitted from the semiconductor laser 3 passes through the light diffusion reflection part 6 and the diffusion transmission member and then exits, speckle noise can be reduced and can be made as close to 0 as possible. The reason is that speckle noise decreases in inverse proportion to the square root of the number of light sources, but by passing through the light diffusion reflection part 6 and the diffusion transmission member, a state where there are countless light sources can be approximated. As a result, the inspection accuracy can be improved.

[0050] In addition, if laser light is used as the light source, due to the monochromaticity of the emitted light, a filter is not required, so the light utilization efficiency is high compared to other light sources, and energy loss can be suppressed. Therefore, for example, simplification of the structure and miniaturization of the device can be achieved by reducing the heat dissipation function and the number of components. Furthermore, since a filter is not used, the output variation depends only on the laser light source, and by using a semiconductor laser 3 or the like as the laser light source, sufficient stability of the output can be ensured.

[0051] Furthermore, since the basic configuration is such that the laser light is introduced from the side peripheral surface 2a of the light guide plate 2 and exits from the plate surface, the device can also be made thinner.

[0052] In addition, the present invention is not limited to the above-described embodiments.

[0053] In the above-described embodiment, the light guide plate 2 is square in plan view, but it may also be rectangular, or may be a polygon, a circle, or the like.

[0054] Mounting substrates 4 may also be provided respectively on the other set of opposite sides of the light guide plate 2, for a total of 4 pieces. Additionally, the mounting substrate 4 (semiconductor laser 3) may also be provided only on one side, rather than being provided on both sides sandwiching the light guide plate 2. The light transmission diffusion member 8 is not necessarily required. This light emitting device can be used not only for an interference fringe inspection device, but also for other inspection devices such as a surface inspection device.

[0055] In addition, the present invention can be variously modified without departing from its gist. Industrial Applicability

[0056] In an interference fringe inspection device or the like, miniaturization, output stability, low cost, and improvement of inspection accuracy can be achieved. Reference Numerals

[0057] 100... Light emitting device (interference fringe inspection device) 2... Light guide plate 2a... Side peripheral surface 2b... One plate surface 2c... The other plate surface 3…Semiconductor laser (laser light source) 6…Light diffusion reflection part 8…Light transmissive diffusion member 9…Reflection plate 9a…Through hole.

Claims

1. An interference fringe inspection apparatus includes a light emitting device that emits inspection light. The interference fringe inspection apparatus is characterized in that the light emitting device includes a light guide plate in the shape of an equal thickness flat plate and a plurality of laser light sources arranged along the side peripheral surface of the light guide plate, and the light emitting device is configured such that the laser light emitted from these laser light sources and guided into the interior from the side peripheral surface of the light guide plate is diffusely reflected by a plurality of light diffusion reflection portions formed on one plate surface of the light guide plate and is emitted from the other plate surface of the light guide plate. The direction in which the angular width of the laser light is configured to be the same as or within a specified range of the thickness direction of the light guide plate.

2. The interference fringe inspection apparatus according to claim 1, characterized in that a reflection plate is disposed between the side peripheral surface of the light guide plate and the laser light source, and the reflection plate is formed with a through hole through which the laser light passes.

3. The interference fringe inspection apparatus according to claim 1, characterized in that the interference fringe inspection apparatus further includes a light transmission diffusion member that is disposed on the other plate surface side of the light guide plate and diffuses light transmission, and the interference fringe inspection apparatus is configured such that the light emitted from the other plate surface of the light guide plate and transmitted through the light transmission diffusion member is emitted to the outside as inspection light.

4. A light emitting device, characterized in that the light emitting device includes a light guide plate in the shape of an equal thickness flat plate and a plurality of laser light sources arranged along the side peripheral surface of the light guide plate, and the light emitting device is configured such that the laser light emitted from these laser light sources and guided into the interior from the side peripheral surface of the light guide plate is diffusely reflected by a plurality of light diffusion reflection portions formed on one plate surface of the light guide plate and is emitted from the other plate surface of the light guide plate. The direction in which the angular width of the laser light is configured to be the same as or within a specified range of the thickness direction of the light guide plate.

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