Foreign matter / defect inspection device, image generation device in foreign matter / defect inspection, and foreign matter / defect inspection method

Abstract

One pixel unit composed of at least one light-receiving element of a light-receiving element array (photodiode array) corresponds one-to-one with a light source, and only when the light source emits light, at least one light-receiving element (one pixel unit) corresponding to the light source detects a light beam. The illumination optical system includes a light guide unit that guides each light beam to an object to be inspected by reducing the interval between the optical axes of the light beams emitted from a plurality of light sources in the arrangement direction of the plurality of light sources.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for inspecting a foreign object, a scratch, unevenness, a defect, a missing part, and an attached foreign object in an inspection object having a thickness in a light-scattering transmission medium, and an image generation apparatus for a detected foreign object. Background Art

[0002] Conventionally, systems mainly employed in surface inspection apparatuses using a light source in a visible region are representative inspection systems such as a combination of a line sensor camera, a contact image sensor (hereinafter referred to as CIS), or a scanning optical system based on a laser beam and a photoelectric conversion element (photomultiplier diode, avalanche photodiode, CCD sensor, CMOS sensor, etc.), a light-receiving optical system including an optical fiber, etc., and most of them are reflection types that receive reflected light and fluorescence from scratches, unevenness, defects, missing parts, attached foreign objects, etc. in an inspection object.

[0003] On the other hand, in a transmission type in which a light-receiving system and an illumination system are arranged opposite each other with an inspection object interposed therebetween, the inspection object is mostly transparent, thin, and has a high transmittance. Moreover, in an inspection object having a thickness, there are few systems for detecting foreign objects, scratches, defects, etc. contained in the inspection object.

[0004] As a non-destructive inspection apparatus, a well-known X-ray inspection apparatus having excellent transmittance uses X-rays as radiation, so it is necessary to set up a radiation management area and the radiation dose to humans must also be managed. That is, the threshold for determining the installation location is high. Moreover, since it is large and heavy, it is not easy to add and introduce it to an existing production line in a factory. In addition, since the price is high, it is not possible to set up many inspection points.

[0005] In addition, in an X-ray inspection apparatus, the good transmittance of X-rays themselves becomes a disadvantage, and even objects such as foreign objects, defects, and scratches will be transmitted, and there are many cases where they cannot be distinguished.

[0006] In an inspection apparatus using a wavelength other than X-rays, when the transmission medium has light-scattering properties, a detection apparatus for foreign objects, scratches, defects, missing parts, etc. contained in the transmission medium cannot be realized.

[0007] In the present invention, not only are there technical problems, but also based on the study of on-site introduction, the simplicity of installation, the danger to the human body, the equipment introduction cost, etc. are considered, and it is premised on using a light source other than X-rays.

[0008] In Patent Document 1, a method for detecting a depression and a bend of a thin film by scanning a laser beam as illumination light in a main scanning direction is disclosed.

[0009] In Patent Document 2, by offsetting the optical axis of the illumination optical system from the optical axis of the light-receiving optical system, the transmitted light of the object to be inspected is prevented from being buried by direct light and interfering light from the illumination optical system. That is, Patent Document 2 is a method of irradiating light on the object to be inspected to utilize the information contained in the shadow of the transmitted light in order to detect foreign matters, defects, etc. inside the object to be inspected. At this time, the following research has been conducted: components such as interfering light that become noise are prevented from mixing into the signals from foreign matters and defects near the surface of the object to be inspected, making it easier to detect foreign matters and defects.

[0010] Patent Document 3 discloses the following: multiple images with an offset pattern of the polarization axis between the illumination side and the light-receiving side are obtained using polarized light, and after contrast adjustment, processing such as differential processing is applied to eliminate noise, enabling accurate detection of foreign matters and defects inside the object to be inspected.

[0011] Patent Document 4 shows that a transmitted image is obtained by aligning the optical axis of the laser beam scanning optical system with the optical axis of the light-receiving optical system that receives the light transmitted through the specimen.

[0012] Prior Art Documents

[0013] Patent Documents

[0014] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-271133

[0015] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2015-219090

[0016] Patent Document 3: Japanese Patent No. 6451980

[0017] Patent Document 4: Japanese Unexamined Patent Application Publication No. 3-134609 Summary of the Invention

[0018] Problems to be Solved by the Invention

[0019] In Patent Document 1, scratches and unevenness on the surface of the object to be inspected are mainly detected. The object to be inspected is mostly a thin material such as a thin film, and inspection can be performed using a CIS with a shallow depth of field. However, when inspecting an object with a thickness and large surface unevenness or a wiring pattern such as a stacked electronic substrate, detection becomes difficult in an existing type of CIS with a depth of field of only 1 to 2 mm. There is a need for a new inspection device with a light-receiving optical system having a deeper depth of field and a long working distance (hereinafter referred to as W.D.).

[0020] Optical systems with a relatively deep depth of field are mainly telecentric optical systems, and line sensor cameras equipped with such optical systems are the mainstream. However, telecentric optical systems are large in size and difficult to be used in narrow transfer paths in factories. Further, when the transfer width of the production line in a factory is relatively wide, the field of view of the telecentric optical system is narrow, so a larger number of cameras are required. Therefore, there is also a difficulty in that the introduction cost becomes high.

[0021] In the case of the optical system of Patent Document 2, when detecting foreign matters, defects, scratches, etc. in a transmissive medium with high light scattering properties, since the light near the optical axis of the illumination optical system is not utilized, the amount of received light of the light-receiving optical system decreases. Moreover, since the transmissive light that can be detected is centered on the scattered light in the inspection object, the interfering light scattered by the inspection object itself becomes the dominant component of the signal component, making it difficult to distinguish and detect the net scattered light scattered by foreign matters in the deeper part of the inspection object.

[0022] In the case of Patent Document 3, there is no problem when the light scattering property of the specimen is small, but when the light scattering ability of the inspection object is large, the polarization information is lost due to polarization cancellation caused by scattering, so it is difficult to produce a difference caused by the deviation mode of the polarization axis, and it is difficult to detect foreign matters and defects in the inspection object that is a light-scattering medium with transmissivity.

[0023] In the case of Patent Document 4, for an inspection object with a thickness, even if it is a medium with a high total light transmittance, due to the main reason of minute refractive index inhomogeneity in the medium, the optical axes of the laser beam scanning optical system and the light-receiving optical system sometimes do not coincide, and the signal itself cannot be obtained. That is, there may also be cases of overlooking foreign matters, scratches, defects, missing parts, etc.

[0024] Based on the above, in the prior art, the depth of field is generally shallow. Therefore, for example, when the inspection object is a food inspection object, a circuit board, etc. with a thickness of 10 mm or more, information in the depth direction cannot be obtained. As a result, it is sometimes impossible to detect foreign matters, defects, scratches, missing parts, etc. Or, the telecentric optical system with a deep depth of field is enlarged, so it is difficult to be arranged in a narrow place. In addition, for example, when performing full inspection of foreign matters in a factory production line, in the above detection methods, scratches and defective parts of an electronic substrate cannot be detected. Especially in the case of foods, etc., there is a risk of overlooking the presence of foreign matter contamination and shipping out.

[0025] As described above, the existing CIS has a shallow depth of field, so information in the depth direction of an inspection object with a thickness cannot be grasped, and thus the reliability of inspection cannot be ensured. In addition, existing methods other than CIS use camera lenses and telecentric optical systems, so enlargement cannot be avoided, and it is difficult to additionally introduce them into existing production lines in factories, especially difficult to additionally introduce them into narrow places.

[0026] In Figure 1 a typical CIS is shown, and also in Figure 2 a linear illumination optical system for the CIS is shown. In Figure 1 it is a cross-sectional view near the central portion in the long side direction of the CIS. Figure 2 is a perspective view. The Z direction is the main scanning direction, and the X direction is the sub-scanning direction. The linear illumination light source 10 is an illumination optical system having an elongated light quantity distribution in the main scanning direction.

[0027] In Figure 1 the CIS shown, two frames 16 are arranged opposite to each other with the focal plane 20 interposed therebetween. In each housing 16, a linear illumination light source 10 for illuminating an object to be inspected located on the focal plane 20 is provided. A lens array 11 and a light receiving portion 12 are provided in one of the housings 16, and light from the illuminated object to be inspected is guided to the light receiving portion 12 by the lens array 11. The lens array 11 is an optical element that images light from the object to be inspected onto the light receiving portion 12. In Figure 1 the CIS shown, with the focal plane 20 as a reference, one of the two linear illumination light sources 10 is arranged on the light receiving portion 12 side, and the other is arranged on the side opposite to the light receiving portion 12 side.

[0028] The light receiving portion 12 is mounted on a substrate 13 fixed to one of the frames 16. The light passing through the lens array 11 is received by the light receiving surface 12A of the light receiving portion 12, and a signal corresponding to the received light quantity is output from the light receiving portion 12. By transporting the object to be inspected along the focal plane 20 in one direction X, the light from the object to be inspected is continuously received by the light receiving portion 12, and an image (color image, fluorescence image, etc.) of the object to be inspected is obtained based on the output signal from the light receiving portion 12.

[0029] The light B3 emitted from one of the linear illumination light sources 10 passes through the protective glass 14 fixed to the housing 16, is reflected by a reflection member 17A provided on the inner surface of the protective glass 14A fixed to the other housing 16, and is guided to the focal plane 20. An ultraviolet light cut-off filter (UV cut-off filter) 15 that blocks ultraviolet light from entering the light receiving portion 12 is provided at an arbitrary position from the focal plane 20 to the light receiving portion 12. In addition, a color filter 18 that allows visible light in a specific wavelength range to pass through is provided between the light receiving portion 12 and the ultraviolet light cut-off filter 15. At a position in one of the housings 16 that faces the bottom surface of the linear illumination light source 10, a substrate 5 for fixing a light source portion 103 (ultraviolet light source, visible light source, etc.) provided in the linear illumination light source 10 is provided.

[0030] The linear illumination light source 10 includes a transparent light guide 101 extending along the length direction L, a light source unit 103 provided near one end face in the length direction L, and a cover member 102 for holding the respective side surfaces of the light guide 101. The light emitted from the light source unit 103 enters the light guide 101, is appropriately reflected by the light diffusion pattern P while propagating in the light guide 101, and is emitted from the light emission surface in the arrow direction, becoming linear illumination light for illuminating the inspection object. However, due to the light guide 101, this illumination optical system diffuses the illumination light, and in an inspection object having a thickness and having light scattering transmissivity, attenuation of the received light amount in the optical axis direction becomes a problem. Further, the depth of field of the existing CIS is relatively shallow, and when the inspection object has a thickness, it is difficult to perform an inspection of the entire thickness direction, and since the W.D. is narrow, there are many cases where contact with the inspection object causes the inspection itself to be impossible. That is, in the existing CIS optical system, it is very difficult to inspect foreign matters, defects, etc. in a transmissive medium having a thickness, and it is even more difficult in the case of having light scattering properties.

[0031] Means for Solving the Problem

[0032] The present inventor conducted in-depth research on the above problems and as a result, found a means capable of detecting foreign matters, defects, scratches, missing parts, etc. even in an inspection object which is a light scattering medium having a thickness of 10 mm or more, and achieving a thin and small size like the existing CIS. In addition, it was also found that even if the inspection object is a transmissive medium having a greater light scattering ability and a thickness, foreign matters, defects, etc. in the inspection object can be detected. Specifically, the following method is provided: by preventing the beam and the scattered light from the foreign matter / defect irradiated by the beam from entering the pixels not irradiated by the beam, and at the same time, taking out the output signal only from at least one light receiving element in one pixel unit corresponding one-to-one to the light source, it is possible to extremely reduce the crosstalk component between pixels and accurately detect foreign matters, defects, etc. in the inspection object. When at least one light receiving element of the light receiving optical system is set as a unit pixel, it is switched to output only by the unit pixel during the residence time of one pixel amount in the light beam scanning of the light scanning illumination light passing through the pixel. If the beam and the scattered light from the foreign matter / defect irradiated by the beam are prevented from entering the pixels not irradiated by the beam, it is possible to extremely reduce the crosstalk component between pixels and accurately detect foreign matters, defects, etc. in the inspection object. Here, the residence time refers to the period during which the approximate center portion of the beam crosses from one end of the one pixel to the other end. If the diameter of the irradiation beam of the illumination optical system is made substantially the same in the depth direction of the inspection object and smaller than the pixel resolution of the light receiving optical system, it is possible to illuminate foreign matters, defects, scratches, missing parts, etc. in the inspection object substantially uniformly.

[0033] In the present invention, a method is proposed that, based on the above-described one-to-one correspondence between the light sources and the light-receiving elements and the relationship between the illumination and the output of the light-receiving elements, enables detection with higher resolution. Specifically, the illumination optical system includes a light guide unit that guides the light beams emitted from a plurality of light sources to an object to be inspected while reducing the interval between the optical axes of the respective light beams in the arrangement direction of the plurality of light sources. In addition, it may also include a unit that magnifies the interval between the optical axes of the respective light beams emitted from the plurality of light sources that have been reduced once so as to coincide with the light-receiving element.

[0034] Advantages of the Invention

[0035] According to the present invention, one pixel unit formed by at least one light-receiving element of a light-receiving element array (photodiode array) corresponds one-to-one with a light source, and only when the light source emits light, the light beam is detected by at least one light-receiving element (one pixel unit) corresponding to the light source. Therefore, for a "foreign object / defect" in which only one collimated or further substantially focused light beam enters the object to be inspected, the light-receiving element can separate and detect only the scattered light. Thus, even for an object to be inspected that has light scattering properties and a thickness, it is possible to detect the "foreign object / defect" with good S / N (extremely little crosstalk). In addition, high-resolution detection is made possible by the light guide unit. In the present invention, the object to be inspected having light scattering properties includes not only a light-scattering transmissive medium but also a reflective medium. In the present invention, since the depth of field on the light source side is relatively deep, even if the reflective medium or the like is the object to be inspected, it is possible to perform "foreign object / defect" inspection. Moreover, even when a thin object such as a thin film moves violently in the vertical direction in the handling system of the process along the optical axis direction, it is possible to perform high-resolution inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a cross-sectional view of a conventional CIS.

[0037] Figure 2 is an exploded perspective view of a linear illumination optical system for a conventional CIS.

[0038] Figure 3A is a schematic diagram of a foreign object / defect inspection device according to the present invention.

[0039] Figure 3B is a schematic diagram showing a first modification of the foreign object / defect inspection device.

[0040] Figure 3C is a schematic diagram showing a second modification of the foreign object / defect inspection device.

[0041] Figure 3D is a schematic diagram showing a third modification of the foreign object / defect inspection device.

[0042] Figure 3EIt is a schematic diagram showing a fourth modified example of a foreign matter / defect inspection device.

[0043] Figure 4A It is a diagram showing the crosstalk of scattered light of the present invention to adjacent pixels.

[0044] Figure 4B It is a diagram showing that a parallel light beam of the present invention is incident on a light-receiving lens array, diffuses after being emitted, and becomes background noise on a light-receiving element.

[0045] Figure 5A It is a signal in which a crosstalk component and a background noise component coexist in the prior art invention.

[0046] Figure 5B It is a signal in the present invention in the case where there is almost no crosstalk component and background noise component.

[0047] Figure 6A It is a graph showing forward scattering of a particle size of 10 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0048] Figure 6B It is a graph showing forward scattering of a particle size of 10 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0049] Figure 6C It is a graph showing forward scattering of a particle size of 17 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0050] Figure 6D It is a graph showing forward scattering of a particle size of 17 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0051] Figure 6E It is a graph showing forward scattering of a particle size of 25 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0052] Figure 6F It is a graph showing forward scattering of a particle size of 25 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0053] Figure 6G It is a graph showing forward scattering of a particle size of 30 μm, showing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0054] Figure 6HIt is a graph showing forward scattering for a particle size of 30 μm, and shows Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica.

[0055] Figure 7 It is a schematic diagram showing the multi-beam illumination-multi-scanning light receiving method of the present invention.

[0056] Figure 8 Represents light scattering caused by non-transmissive "foreign matter / defects".

[0057] Figure 9A It is a schematic diagram showing an embodiment of a reflective type.

[0058] Figure 9B It is a schematic diagram showing another embodiment of the reflective type of the present invention.

[0059] Figure 10 This is a schematic diagram of another method of further reducing the crosstalk component of the present invention, which is a method of providing an aperture (array) corresponding to each fly-eye lens of the light receiving system.

[0060] Figure 11 It is a schematic diagram (a cross-sectional view viewed from the optical axis direction) showing how adjacent collimated light beams overlap.

[0061] Figure 12A It is a schematic diagram of an experiment of the edge method of the present invention.

[0062] Figure 12B It is a schematic diagram of an experiment of the edge method of the prior art.

[0063] Figure 13 is the beam profile of the LD in the embodiment of the present invention.

[0064] Figure 14A In the embodiment of the present invention, (1) a graph showing the response of edge signals in the case of two diffusion plates (standard value), and (2) a graph showing the difference between adjacent pixels of edge response signals (standard value).

[0065] Figure 14B : In the embodiment of the present invention, (1) a graph showing the response of edge signals in the case of three diffusion plates (standard value), and (2) a graph showing the difference between adjacent pixels of edge response signals (standard value).

[0066] Figure 14C : In the embodiment of the present invention, (1) a graph showing the response of edge signals in the case of four diffusion plates (standard value), and (2) a graph showing the difference between adjacent pixels of edge response signals (standard value).

[0067] Figure 14D: In an embodiment of the present invention, (1) is a graph (standard value) showing the response of the edge signal in the case of five diffusion plates, and (2) is the difference between adjacent pixels of the edge response signal (standard value).

[0068] Figure 15A : According to the existing method, (1) is a graph (standard value) showing the response of the edge signal in the case of two diffusion plates, and (2) is the difference between adjacent pixels of the edge response signal (standard value).

[0069] Figure 15B : According to the existing method, (1) is a graph (standard value) showing the response of the edge signal in the case of three diffusion plates, and (2) is the difference between adjacent pixels of the edge response signal (standard value).

[0070] Figure 15C : According to the existing method, (1) is a graph (standard value) showing the response of the edge signal in the case of four diffusion plates, and (2) is the difference between adjacent pixels of the edge response signal (standard value).

[0071] Figure 15D : According to the existing method, (1) is a graph (standard value) showing the response of the edge signal in the case of five diffusion plates, and (2) is the difference between adjacent pixels of the edge response signal (standard value).

[0072] Figure 16 is a schematic diagram showing the simulation model of the present invention.

[0073] Figure 17A is a graph showing the result of the simulation, indicating the case where the foreign object particle is located at the center of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.00 wt%.

[0074] Figure 17B is a graph showing the result of the simulation, indicating the case where the foreign object particle is located at the center of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.04 wt%.

[0075] Figure 17C is a graph showing the result of the simulation, indicating the case where the foreign object particle is located at the center of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.08 wt%.

[0076] Figure 17D is a graph showing the result of the simulation, indicating the case where the foreign object particle is located at the center of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.12 wt%.

[0077] Figure 17EIt is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the center of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.16 wt%.

[0078] Figure 17F It is a curve graph showing the result of simulation when the foreign object particle is located at the center of the light-scattering transmissive medium, representing the output comparison at various concentrations of the light-scattering transmissive medium.

[0079] Figure 18A It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light source side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.00 wt%.

[0080] Figure 18B It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light source side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.04 wt%.

[0081] Figure 18C It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light source side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.08 wt%.

[0082] Figure 18D It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light source side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.12 wt%.

[0083] Figure 18E It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light source side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.16 wt%.

[0084] Figure 18F It is a curve graph showing the result of simulation when the foreign object particle is located at the light source side end of the light-scattering transmissive medium, representing the output comparison at various concentrations.

[0085] Figure 19A It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light-receiving sensor side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.00 wt%.

[0086] Figure 19B It is a curve graph showing the result of simulation, representing the case where the foreign object particle is located at the light-receiving sensor side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.04 wt%.

[0087] Figure 19CIt is a graph showing the result of simulation, indicating the case where the foreign object particle is located at the light-receiving sensor side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.08 wt%.

[0088] Figure 19D It is a graph showing the result of simulation, indicating the case where the foreign object particle is located at the light-receiving sensor side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.12 wt%.

[0089] Figure 19E It is a graph showing the result of simulation, indicating the case where the foreign object particle is located at the light-receiving sensor side end of the light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.16 wt%.

[0090] Figure 19F It is a graph showing the result of simulation in the case where the foreign object particle is located at the light-receiving sensor side end of the light-scattering transmissive medium, indicating the output comparison at each concentration.

[0091] Figure 20 It is a schematic diagram showing a one-to-one correspondence of a plurality of pixels each composed of a plurality of light sources arranged in the main scanning direction and at least one light-receiving element.

[0092] Figure 21 It is a conceptual diagram of an inspection method based on the prior art.

[0093] Figure 22 It shows the following method: when inspecting the thickness of the object to be inspected and when the depth of field of the light-receiving lens array is narrower than the thickness of the object to be inspected, the depth of field position is shifted in the optical axis direction, and the scattered light is branched by a beam splitter, enabling detection in the entire thickness direction of the object to be inspected. Detailed implementation mode

[0094] Hereinafter, in the present invention, the scars, unevenness, defects, missing parts, foreign objects attached, etc. in the inspection object having the above-mentioned foreign objects and thickness are simply referred to as "foreign objects / defects". As a schematic diagram, in Figure 3A An example of the foreign object / defect inspection device according to the present invention is shown. However, an image generation device that processes the signals obtained in the foreign object / defect inspection device into image information and outputs it can also be provided.

[0095] Figure 3A The reference numeral 31 in Figure 3AThe solid line of the light source 31 is a side view, and the two-dot chain line virtually shows a front view of the light source 31 to the side of the solid line. Each light beam emitted from the plurality of light sources 31 is guided to the inspection object 34 by the light guide unit 32.

[0096] The light guide unit 32 includes a collimating lens array 32a, an optical fiber array 32b, and a lens array 32c. In the collimating lens array 32a, a plurality of collimating lenses 32d are arranged in a straight line. The number of arranged collimating lenses 32d is the same as the number of light sources 31, but the interval between adjacent collimating lenses 32d is smaller than the interval between adjacent light sources 31. In the lens array 32c, a plurality of lenses 32f are arranged in a straight line. The number of arranged lenses 32f is the same as the number of light sources 31, and the interval between adjacent lenses 32f is also consistent with the interval between adjacent light sources 31. The optical fiber array 32b optically connects the collimating lens array 32a and the lens array 32c. Specifically, the optical fiber array 32b includes the same number of optical fibers 32e as the light sources 31, and each optical fiber 32e corresponds one-to-one to each collimating lens 32d and each lens 32f.

[0097] Each lens 32f of the lens array 32c is opposite to the position of each light source 31. The lens array 32c is used to guide the light from each light source 31 to each optical fiber 32e, and each lens 32f is arranged roughly in close contact with the incident side end face of each optical fiber 32e. The lens 32f used for the lens array 32c is preferably a microsphere lens, a refractive index distribution lens, etc. Each optical fiber 32e is fixed in a linear arrangement on the emission side, and the interval is narrower than the incident side, and is set to an interval equal to the spacing of the light receiving elements in the light receiving element array 38 (photodiode array). That is, the interval between the respective emission ends (ends on the collimating lens 32d side) of the plurality of optical fibers 32e into which each light beam emitted from the plurality of light sources 31 is injected is smaller than the interval between the respective injection ends (ends on the lens side). Thus, the interval between the optical axes of each light beam emitted from the plurality of light sources 31 can be reduced in the arrangement direction of the plurality of light sources 31 and guided to the inspection object 34.

[0098] The light emitted from each optical fiber 32e passes through a collimating lens 32d composed of a micro lens such as a microsphere lens, etc., and thus becomes a collimated light beam. In this way, the plurality of collimating lenses 32d collimate the emitted light from each optical fiber 32e in a one-to-one correspondence with the emission ends of the respective optical fibers 32e. The arrangement direction of the plurality of collimating lenses 32d arranged in the same number as the plurality of light sources 31 is the same as the arrangement direction of the light receiving elements. The pitch of the arrangement direction of the optical fibers 32e needs to be approximately the same as the pitch of the light receiving elements (photodiodes), and thus an optical fiber 32e with a small outer diameter (cladding diameter or coating diameter) is preferred. In addition, the light source 31 is also preferably a light source with low coherence. Examples of the above optical fiber 32e include SI (step) type, GI (graded index) type, single mode type, etc. In addition, the arrangement direction of the illumination system is parallel to the arrangement direction of the elements of the light receiving system.

[0099] The above advantages are that the constraints on the size of the light source 31 are reduced, and the line illumination system on the emission side can be arranged more densely than the light source 31 side. In addition, heat dissipation countermeasures also become relatively easy, resulting in an increase in the light output of LD and LED, an improvement in the operating stability, durability, etc.

[0100] The light emitted from each optical fiber 32e is collimated by the collimating lens 32d and becomes a substantially parallel light beam 33 having the same number as the light sources 31. Figure 3AThe collimating lens array 32a represented by the solid line is a side view, and the main view of the collimating lens array 32a is virtually represented by a double-dashed line on the side of the collimating lens array 32a represented by the solid line. A plurality of roughly parallel light beams 33 are incident on the inspection object 34, and the scattered light 36 scattered by the "foreign matter / defect" 35 in the inspection object 34 is captured within the depth of field of the light receiving lens array 37, focused to the focal position 39 of the light receiving lens array 37, and incident on the light receiving element array 38. The light receiving element array 38 generally has a line sensor in the sub-scanning direction, but it can also have multiple line sensors or area sensors in the sub-scanning direction. The light receiving lens array 37 is preferably a refractive index distribution lens array represented by a SELFOC lens, but it can also be a lens array in which a plurality of other spherical lenses are arranged in a linear shape. In addition, it can also be a structure in which the light collimated by the collimating lens 32d is further roughly focused. Here, "roughly focusing" is not limited to a structure that focuses the light emitted by an LED, but also includes the case where a focusing lens or the like is used to form the beam waist of a laser beam. The size (beam diameter) of the light beam collimated by the collimating lens 32d, or the light beam after the collimated light beam is further roughly focused, is preferably about 10 μm corresponding to the "foreign matter / defect" particles in the Mie scattering region to about 1000 μm corresponding to the "foreign matter / defect" particles in the geometric optical approximation region. However, it is also possible to adjust the light collimated by the collimating lens 32d in a manner of shrinking it or expanding it according to the depth and thickness of the light scattering transmissive medium.

[0101] When there is no "foreign matter / defect" in the inspection object, the light is incident on the light receiving lens array 37 in a state of substantially parallel light beams, and therefore is not focused, but diverges at the focal position 39 of the light receiving lens array 37, and the direct light is attenuated and becomes a bias component in the light receiving element array (photodiode array) 38. Therefore, in the light receiving element array (photodiode array) 38, only the signal component (variation component) of the scattered light 36 caused by the "foreign matter / defect" with the bias component of the direct light added or subtracted is detected.

[0102] Here, a method for suppressing crosstalk components in the light-receiving element array (photodiode array) 38 will be described. When the light sources are lit simultaneously, the illumination light is linearly distributed in the arrangement direction of the light-receiving element array (photodiode array) 38. Therefore, in a situation where "foreign matter / defects" are arranged along the arrangement direction, the same light-receiving element (photodiode) simultaneously receives scattered light from "foreign matter / defects" at different positions, making it difficult to determine the position. That is, the position detection resolution is reduced. The crosstalk avoidance method is to make one light source correspond to one photodiode. That is, making the light sources and the light-receiving elements (photodiodes) correspond one-to-one on a per-pixel basis is one of the means to avoid crosstalk. One pixel is composed of at least one light-receiving element, but it is not limited to a structure where one pixel is composed of one light-receiving element. One pixel can also have a structure composed of multiple light-receiving elements.

[0103] Explain again Figure 3A as follows. In Figure 3A , a combination of multiple light sources and light-receiving elements is provided on one inspection surface of the object to be inspected. In this case, it is preferable to scan the light beam in the main scanning direction (the arrangement direction of the multiple light sources) by sequentially lighting the multiple light sources so that adjacent light sources are not lit simultaneously. At this time, a control unit (not shown) capable of individually controlling the operation of each light source functions as a light scanning unit for scanning the light beam. This light scanning unit, the light source 31, the light guide unit 32, etc. constitute an illumination optical system. On the other hand, the light-receiving element array (photodiode array) 38 constitutes a light-receiving optical system. In addition, the light-receiving lens array 37 constitutes a lens system that images the light transmitted through the inspection surface of the object to be inspected on the light-receiving elements of the light-receiving element array (photodiode array) 38, and this lens system is included in the light-receiving optical system. The combination of the illumination optical system and the light-receiving optical system can either be movable in the optical axis direction or be multiple illumination optical systems and light-receiving optical systems whose depths of field do not overlap in the optical axis direction corresponding to multiple inspection surfaces. When there are multiple illumination optical systems, for example, it can be a structure where multiple linearly separated light sources 31 have multiple lines. In this case, it can be multiple linearly arranged light sources 31 of the same wavelength, or multiple linearly arranged light sources 31 of different wavelengths. When only the light-receiving optical systems do not overlap in the optical axis direction, various units for splitting light are used in the light-receiving optical system. For example, there is a method of using one or more optical elements such as beam splitters. Or, there is also a method of separating each wavelength with a dichroic mirror to distinguish the types of foreign matter.

[0104] Figure 3B is a schematic diagram showing a first modified example of the "foreign matter / defect" inspection device. Figure 3BShows a structure for further improving the resolution by further reducing the pitch of the light-receiving elements (photodiodes). In this example, the light guide unit 32 includes a combined lens (reduced combined lens) 32g formed by a combination of a plurality of lenses.

[0105] The combined lens 32g is disposed between the optical fiber array 32b and the inspection object 34. More specifically, it is disposed between the collimating lens array 32a and the inspection object 34. The combined lens 32g is composed of, for example, a set of cylindrical lenses formed by a combination of convex-convex. Thus, the interval between the optical axes of the respective light beams emitted through the combined lens 32g is smaller than the interval between the optical axes of the respective light beams incident on the combined lens 32g. In this way, through a set of cylindrical lenses with different focal lengths, the pitch of the collimated light beams is appropriately reduced by a reduction ratio and can be made equal to the pitch of a higher-resolution and finer light-receiving element array (photodiode array).

[0106] Figure 3C Is a schematic diagram showing a second modified example of the "foreign matter / defect" inspection device. Similar to Figure 3B the case of, Figure 3C Shows a structure in the case of further improving the resolution by further reducing the pitch of the light-receiving elements (photodiodes). In this example, the combined lens (reduced combined lens) 32h included in the light guide unit 32 is not formed by a combination of convex-convex, but is composed of a set of cylindrical lenses formed by a combination of convex-concave. The convex cylindrical lens is disposed on the collimating lens array 32a side, and the concave cylindrical lens is disposed on the inspection object 34 side. Even with such a structure, it is possible to make the interval between the optical axes of the respective light beams emitted through the combined lens 32h smaller than the interval between the optical axes of the respective light beams incident on the combined lens 32h.

[0107] In Figures 3A - 3C the structure using the optical fiber array 32b has been described, but it is not limited to such a structure. Currently, typified by LED printers, the high density of LEDs is continuously developing, and 1200 dpi has been achieved. If this LED array is used, high resolution can be achieved. That is, the emitted light emitted from the LED array is collimated, and the collimated light beam is replaced with Figure 3B or Figure 3C the light source of and used. In the case of an LED printer, the lens array is an equal-magnification imaging system of a refractive index distribution type lens, but the refractive index distribution type lens used in the present invention uses a lens with one focus located at infinity. Additionally, it is more preferable to use a high-density LD array such as a VCSEL. Regarding the above method, specific examples will be described below.

[0108] Figure 3D3 is a schematic diagram showing a third modified example of the "foreign matter / defect" inspection device. In this example, a combined lens (reducing combined lens) 32i is used instead of the optical fiber array 32b, so that the intervals between the optical axes of the light beams emitted from the plurality of light sources 31 can be reduced in the arrangement direction of the plurality of light sources 31 and guided toward the inspection object 34. That is, the light guide unit 32 includes a combined lens 32i composed of a combination of a plurality of lenses.

[0109] Reference numeral 31 is an LED or LD array as a light source, and reference numeral 32a is a collimating lens array. Figure 3D The light source 31 and the collimating lens array 32a shown by the solid line are side views, and the front views of the light source 31 and the collimating lens array 32a are respectively shown by double-dashed lines on the sides of the light source 31 and the collimating lens array 32a shown by the solid line. Reference numeral 34 is an inspection object, and reference numeral 35 is a foreign matter or defect in the inspection object. Reference numeral 37 is a light receiving lens array. Reference numeral 38 is a light receiving element array (photodiode array). In addition, reference numeral 30 is a light beam emitted from the light source 31, and reference numeral 33 is a collimated light beam emitted from the collimating lens array 32a. The collimated light beam 33 is incident on the inspection object 34, and then is incident on the "foreign matter / defect" 35. The light beam 33 incident on the "foreign matter / defect" 35 is scattered by the "foreign matter / defect" 35 to become scattered light 36, which is incident on the light receiving lens array 37, and then is incident on the light receiving element array 38.

[0110] The combined lens 32i is arranged between the plurality of light sources 31 and the inspection object 34, more specifically, between the collimating lens array 32a and the inspection object 34. The combined lens 32i is composed of a group of cylindrical lenses composed of, for example, a convex-convex combination, but may also be composed of a convex-concave combination. Thus, the interval between the optical axes of the light beams emitted through the combined lens 32i is smaller than the interval between the optical axes of the light beams incident on the combined lens 32i.

[0111] Figure 3E is a schematic diagram showing a fourth variant of the "foreign matter / defect" inspection device. In this example, Figure 3D A combined lens (magnifying combined lens) 32k is added to the structure. However, it is also possible not to Figure 3D structure, but in Figure 3B or Figure 3C A combined lens 32k is added to the structure.

[0112] The combined lens 32k is disposed between the inspection object 34 and the light-receiving element array 38. More specifically, it is disposed between the inspection object 34 and the light-receiving lens array 37. The combined lens 32k is composed of a set of cylindrical lenses formed by, for example, a convex-convex combination, but it can also be formed by a convex-concave combination. Thus, the interval between the optical axes of the respective light beams emitted through the combined lens 32k is larger than the interval between the optical axes of the respective light beams incident on the combined lens 32k.

[0113] As in this example, if beam adjustment is performed using a reduction optical system and beam expansion (enlarging the beam interval) is performed after the foreign matter passes through, the interval between the light-receiving elements can be enlarged. Therefore, since the size of the light-receiving element array can be made larger, the resolution for foreign matter can be ensured, and the light-receiving area of the light-receiving element array can be enlarged. As a result, the S / N can be made good.

[0114] constitute Figures 3B - 3E The multiple lenses of the combined lenses 32g, 32h, 32i, 32k shown each have a focal power in the arrangement direction of the multiple light sources 31. Here, the focal power of a lens is the reciprocal of the focal length and is a measure representing the refractive power of the lens. The combined lenses 32g, 32h, 32i, 32k are each composed of a combination of lenses with different focal powers. That is, the compression ratio can be changed by a combination of a lens with a larger focal power and a lens with a smaller focal power. For example, if the focal power ratio is 1:3, the compression ratio is 1 / 3 and the beam interval is 1 / 3.

[0115] The number of lenses constituting the combined lenses 32g, 32h, 32i, 32k is not limited to two and can also be three or more. In addition, the lenses constituting the combined lens are not limited to cylindrical lenses and can also be other reduction / enlargement optical elements such as a fiber optic faceplate. In addition, it can also be a combination of a cylindrical mirror and a cylindrical mirror with different focal powers, or a combination of a cylindrical mirror and a cylindrical lens with different focal powers, etc., and can also be various combinations of spherical lenses and spherical mirrors. In addition to this, various lenses such as Fresnel lenses can also be used.

[0116] Next, Figure 22 A method of branching using a beam splitter is shown. Figure 22 It represents the following method: When the inspection object 34 is thick and the depth of field of the light-receiving lens array 37 is narrower than the thickness of the inspection object 34, the depth of field position is shifted in the optical axis direction, and the scattered light is branched using the beam splitters 40a, 40b, and detection can be performed in the entire thickness direction of the inspection object 34. In Figure 22There are respectively provided three light-receiving lens arrays 37a, 37b, 37c, light-receiving element arrays 38a, 38b, 38c, and two beam splitters 40a, 40b. The inspection object 34 has a plurality of depth-of-field regions A1 to A3 in the optical axis direction. The light-receiving lens array 37a and the light-receiving element array 38a correspond to the depth-of-field region A1, the light-receiving lens array 37b and the light-receiving element array 38b correspond to the depth-of-field region A2, and the light-receiving lens array 37c and the light-receiving element array 38c correspond to the depth-of-field region A3. A part of the light transmitted through the inspection object 34 is reflected by the beam splitter 40a, condensed by the light-receiving lens array 37a, and incident on the light-receiving element array 38a. In addition, a part of the light passing through the beam splitter 40a is reflected by the beam splitter 40b, condensed by the light-receiving lens array 37b, and incident on the light-receiving element array 38b. The light passing through the beam splitter 40b is condensed by the light-receiving lens array 37c and incident on the light-receiving element array 38c. The transmittance and reflectance of each of the beam splitters 40a, 40b are made equal with respect to each of the light-receiving element arrays 38a, 38b, 38c. For example, as Figure 22 shown, in the case of three branches, by setting the reflectance of the initially incident beam splitter 40a to approximately 33% and the reflectance of the subsequently incident beam splitter 40b to 50%, the amount of light incident on each of the light-receiving element arrays 38a, 38b, 38c can be made approximately 1:1:1, and the S / N is also approximately equal. As the beam splitter, a beam splitter having no wavelength dependence and not utilizing an interference effect is preferred.

[0117] Here, regarding the embodiment of the present invention, a summary is now made. Figure 20 is a schematic diagram showing one-to-one correspondence between a plurality of light sources of the present invention and a plurality of pixels including at least one light-receiving element.

[0118] Next, Figure 21 is a conceptual diagram showing an inspection method of the prior art. However, for simplicity, the light-receiving lens system is not shown. Figure 21 In the prior art, the light source illuminates the entire inspection object. In addition, it is known that the light-receiving element is divided into scattered light and non-scattered light directly directed toward the light-receiving element. The non-scattered light contributes to foreign object detection, but does not enter the foreign object, but is mixed into the non-scattered light directly directed toward the light-receiving element from other paths of the inspection object other than the foreign object, resulting in crosstalk.

[0119] In contrast, in Figure 20 the case, a plurality of light sources (light source arrays) arranged separately in the main scanning direction are appropriately in one-to-one correspondence. In the Figure 20 conceptual diagram shown, since the light source and the light-receiving element are in one-to-one correspondence, scattered light is difficult to enter the light-receiving element, and crosstalk can be suppressed.

[0120] Actual "foreign objects / defects" are hardly perfect spheres, but for simplicity, they are typically represented as spherical particles. When the foreign objects have a particle size of around 10 μm or less in wavelength, scattering in the Mie scattering region occurs. Additionally, if the size is around 100 μm like raindrops, geometric optical approximation can be applied. For example, consider the case of a spherical particle with a diameter of 10 μm, a light-scattering transmission medium of resin, and the foreign object being silica. The wavelength of the light from the light source is not limited to a single wavelength, and it can also have an illumination light source with multiple wavelengths. Now, if the wavelength of the light from the light source is set to λ = 830 nm in the near-infrared region, the above resin is set to polycarbonate at this time, the relative refractive index is set to Nm = 1.57, the foreign object particles are set to silica, and its relative refractive index is set to Np = 1.45, then forward scattering occurs. For a particle size of around 100 μm, if it is transmissive with respect to the light source wavelength, it is focused and diffused forward due to the lens effect, and if it is completely non-transmissive, it becomes the scattering cross-section projected by geometric optics, that is, the shadow of a circle. The shadow is represented by the intensity of the absorbed / diffused reflected and transmitted diffused light. Sometimes, it is also necessary to consider the influence of diffraction caused by the edges of the foreign object particles, but whether it is projecting scattered light including diffraction or a shadow onto the pixel, as long as the sensitivity to its contrast is sensitive enough. As an example, the scattered light intensity of the above spherical particle scattering is shown in Figures 6A - 6D . Figure 6A And Figure 6B is a graph showing the forward scattering of a 10-μm particle size, Figure 6C And Figure 6D is a graph showing the forward scattering of a 17-μm particle size, representing Mie scattering (logarithmic scale) when the transmissive medium is polycarbonate and the particles are silica. It can be seen that the intensity of the forward scattered light is very strong. The 0-degree direction (the direction of the arrow) is the direction of light travel. Additionally, it can also be seen that, at the same time, compared with 10 μm, the forward scattering ability of a 17-μm particle size is about several times stronger. Further, the graph showing the forward scattering of foreign object particles with a particle size of 25 μm is shown in Figure 6E , Figure 6F . Among them, the wavelength of the incident light is λ = 1.55 μm. The forward scattering intensity in this case is between the 10-μm particle size and the 17-μm particle size. Incidentally, a 25-μm particle size is close to the resolution of 1200 dpi (pixel resolution: about 21 μm), and a 10-μm particle size is close to the resolution of 2400 dpi (pixel resolution: stronger than 10 μm). Additionally, the graph showing the Mie scattering of foreign object particles with a particle size of 30 μm with an incident light wavelength of 1.55 μm is as shown in Figure 6G , Figure 6H . It can be seen that the forward scattering intensity of a 30-μm particle size is about 2 times that of the 25-μm particle size case.

[0121] Hereinafter, a method for suppressing the crosstalk component, which is a simplified notation for the scattered light in the Mie forward scattering region, will be described. First, use Figure 4A for the description. Figure 4A is a schematic diagram of receiving scattered light from "foreign matter / defects", showing the crosstalk of the scattered light to adjacent pixels. The star-shaped mark 41 represents foreign matter (defect). The scattered light from the foreign matter (defect) 41 is condensed by the light-receiving lens array 42 and imaged on the light-receiving element array (photodiode array) 43. In Figure 4A , a case where a plurality of independent light beams are simultaneously incident on the foreign matter is shown.

[0122] Figure 4A The bell-shaped light intensity distribution waveform If on the left side represents the intensity distribution of the scattered light incident on the light-receiving element array (photodiode array) 43. The scattered light incident on the light-receiving element array (photodiode array) 43 is larger than the actual size of the "foreign matter / defect" due to the aberration and diffraction of the light-receiving lens, and is imaged in a so-called blurred state. That is, assuming that in the arrangement direction of the light-receiving element array (photodiode array) 43, even if the size of one pixel of the light-receiving element (photodiode) is the same as the size of the "foreign matter / defect", the imaging size of the "foreign matter / defect" on the light-receiving element (photodiode) 43 is larger than the size of the "foreign matter / defect" due to the aberration and diffraction of the light-receiving lens. Preferably, the aperture angle of the light-receiving lens is small enough with respect to the incident angle of the scattered light, diffused light, or light with strong and weak intensity that is absorbed / diffused reflected and transmitted / diffused in the light transmitted through the inspection surface of the inspection object to the light-receiving lens. For example, the aperture angle is preferably about 5 mrad to 15 mrad, and can be 1 mrad to 20 mrad according to the desired W.D. If the aperture angle becomes smaller, the amount of received light becomes less, so it is necessary to compensate relatively with the focal power on the light source side. Further, since the transmittance depending on the thickness of the light-scattering transmission medium is directly related to the gain of the light-receiving sensor, by providing a circuit structure with automatic gain control (denoted as AGC) in the light-receiving sensor, a light-receiving system with good S / N and a wide dynamic range that is not dependent on various transmittances can be constructed. In addition, at this time, a feedback system (signal processing circuit system) can also be used for any pixel, and this feedback system uses the average value of the outputs immediately before the output of any pixel. In addition, if a two-dimensional analysis in the depth direction of the inspection object of the comprehensive information (output data) of the position-output information of the signal taken in row by row is performed simultaneously, real-time inspection can also be performed. In any case, in order to make the S / N quality of the signal good, research is carried out to match the maximum sensitivity range of the light-receiving sensor, so as to further improve the S / N of the signal. As a result, the applicable range in the "defect / foreign matter" inspection is expanded. Figure 4AThe bell-shaped light intensity distribution waveform Ir on the right side is the intensity distribution of each beam of light for illuminating foreign objects in the present invention. If the widths of the light intensity distribution waveforms on the left and right in the arrangement direction on the side of the light receiving element array (photodiode array) 43 are compared, it can be seen that the light intensity distribution waveform If on the side of the light receiving element array (photodiode array) 43 is wider than the light intensity distribution waveform Ir on the incident side.

[0123] Next, the two light intensity distribution waveforms If of the light receiving element array (photodiode array) 43 will be described. In the light scattering medium Ms, two "foreign objects / defects" Mf1 and Mf2 are arranged in parallel with the light receiving element array (photodiode array) 43 opposite to the light receiving element array (photodiode array) 43, and their intervals are the same as the element intervals of the light receiving element array (photodiode array) 43. In addition, the light receiving lens array 42 is an equal magnification system, and the W.D. is lengthened in advance.

[0124] In this case, it can be seen that the light intensity distribution waveform If1 formed by imaging one of the "foreign objects / defects" Mf1 and Mf2 also spreads to the light receiving element (photodiode) PD2 adjacent to the light receiving element (photodiode) PD1 opposite to itself, generating crosstalk. The parts where crosstalk occurs are the hatched parts Cr1 and Cr2 of each light intensity distribution waveform.

[0125] In other words, the light intensity components Cr1 and Cr2 observed from adjacent pixels are added to the net signal component of itself. This is because the crosstalk components mixed into the net signal components of the light receiving elements (photodiodes) become noise, so the dynamic range becomes narrow, which is one of the main reasons for deteriorating the SNR (Signal to Noise Ratio: synonymous with S / N) of the signal.

[0126] Next, an explanation will be given for Figure 4B is a schematic diagram showing that the collimated light beam is incident on the light receiving lens array 42, spreads after being emitted, and becomes background noise on the light receiving elements PD1 and PD2. The illumination used in existing CIS, etc. has a continuous light intensity distribution in the length direction of the light receiving element array (photodiode array) 43. The light scattered by the "foreign objects / defects" in the light scattering medium Ms is Figure 4B Figure 4A ​44. On this basis, the collimated light beam 45 is incident on the light receiving lens array 42. Since the light receiving lens array 42 is set as an equal magnification system, light from outside the vicinity of its depth of field is hardly focused. That is, due to divergence, it does not contribute to imaging, so it spreads on the light receiving element array (photodiode array) 43. That is, when the collimated light beam is incident on the light receiving lens array 42, it spreads significantly on the light receiving element array (photodiode array) 43 and becomes the background noise component 46, which is the main cause of the deterioration of the S / N. The background noise component 46 is represented by the part surrounded by the square dotted line. If the background noise increases, it will lead to the deterioration of the contrast. That is, in the "foreign matter / defect" detection, it is buried in the background noise component and the detection becomes difficult.

[0127] The actually detected signal is a mixture of the above-mentioned crosstalk component and background noise component, and as a result, it becomes Figure 5A the signal shown. Figure 5B The case where there are almost no crosstalk components and background components is shown. In addition, in the case of geometric optical scattering, due to the shielding effect, the intensity distribution of the "foreign matter / defect" becomes a distribution similar to that of Figure 8 described later.

[0128] In addition to the method of illuminating the light receiving element (photodiode) and the light source shown in the present invention in a one-to-one correspondence per pixel unit, a method for further reducing the crosstalk component will be described. As Figures 3A - 3E shown, Figures 3A - 3EAs shown, in the method of linear illumination, components from a light source adjacent to an adjacent photodiode are mixed in. The method to avoid this is not to light up simultaneously, but to operate only a pair of light sources and a light-receiving element (photodiode) per pixel unit that are in one-to-one correspondence, and then move to an adjacent combination of a pair of light sources and a light-receiving element (photodiode) per pixel unit that are in one-to-one correspondence, and repeat this sequentially until the end. That is, only the light-receiving elements of a corresponding pixel unit detect the light beam from a light source at any position in the main scanning direction. Such control can be performed by individually switching the on / off states of each light source and each light-receiving element by a control unit (not shown) including a CPU. At this time, the control unit functions as a detection unit. More specifically, in synchronization with the scanning of the light beam in the illumination optical system, signals are output only to the light-receiving elements near the center of the light beam at each scanning position among the plurality of light-receiving elements. Thus, assuming that the light beam diameter is large and the light beam emitted from one light source and collimated by a collimating lens is scattered by "foreign matter / defect", when this scattered light enters the light-receiving elements (photodiodes) that are in one-to-one correspondence per pixel unit, even if it enters adjacent pixels or neighboring pixels, the adjacent or neighboring pixels do not output, so only the net signal for the "foreign matter / defect" corresponding to the light source and at least one light-receiving element (photodiode) per pixel unit that are in one-to-one correspondence is obtained. At this time, since the above-mentioned crosstalk components do not output from other pixels, only the collimated light beam component entering the light-receiving lens array is received, and the crosstalk is very small.

[0129] It is shown in Figure 7 in. Figure 7 It is a schematic diagram showing the multi-beam illumination - multi-scan light-receiving method. 71 is the light intensity distribution of the incident light beam, and 72 is the scattered light. 73 is the light beam when the light passing through the light-receiving lens array 74 is condensed onto the light-receiving element array (photodiode array) 75. The projected images of the scattered light of the "foreign matter / defects" Mr1 and Mr2 in the inspection object 76 are Imf1 and Imf2. The imaging size at this time is larger than the actual size of the "foreign matter / defect" as described above, and the imaging size in the arrangement direction of the light-receiving element array (photodiode array) 75 becomes larger and blurred due to aberration and diffraction. However, since the position where the light beam enters is limited and the output of pixels other than the pixels in one-to-one correspondence is restricted, there is no output from pixels other than the pixel 77 corresponding to the incident light beam.

[0130] In addition, it is also possible to simultaneously irradiate other pixels 77 at positions where crosstalk does not become a problem with the incident light beams in one-to-one correspondence. In this case, as Figure 7As shown, multiple illuminations can be performed simultaneously at the same timing, thus having the advantage of shortening the scanning time. This method is called the "multi-beam illumination - multi-scan light reception method", which is different from the above-mentioned "one-beam illumination - one-scan light reception method".

[0131] The spatial resolution of one pixel unit composed of at least one light-receiving element is equal to or higher than the spatial resolution of the light beam on the inspection surface of the object to be inspected. Here, the spatial resolution of the light beam corresponds to the beam diameter of the light beam on the inspection surface of the object to be inspected. That is, in one pixel unit composed of at least one light-receiving element, there is an ability to distinguish two points approaching within the beam diameter of the light beam. In other words, the spatial resolution of the light beam is equal to or lower than the spatial resolution of the pixel unit composed of at least one light-receiving element arranged along the main scanning direction.

[0132] The scanning interval of the light beam can also be equal to or lower than the spatial resolution of the pixel unit composed of at least one light-receiving element arranged in the main scanning direction. In other words, the spatial resolution of the pixel unit composed of at least one light-receiving element is equal to or higher than the scanning interval of the light beam. That is, in one pixel unit composed of at least one light-receiving element, there is an ability to distinguish two points approaching at the scanning interval of the light beam (the interval of the light sources).

[0133] Next, the case where the "foreign matter / defect" in the object to be inspected is in the geometric optical scattering region or is non-transmissive is described. The scattering of the above-mentioned "foreign matter / defect" is shown in Figure 8 . Figure 8 The Cr (the shaded part) is the crosstalk component of the element (center) that makes the illumination light beam of the adjacent pixel 77 act. The transmission component is the intensity distribution lower than the peak of the intensity distribution of the adjacent bell shape. Since the output of the central pixel is low and the output of the adjacent pixel is high, the presence of the "foreign matter / defect" Mr can be detected.

[0134] As described above, whether the "foreign matter / defect" in the object to be inspected is in the Mie scattering region, the geometric optical scattering region, or is transmissive or non-transmissive, and further, the form of the signal changes according to the surface property, dielectric constant, etc. However, the "foreign matter / defect" can be detected based on the level of the detected signal. And if the strength and signal waveform of the signal caused by the foreign matter are used as a look-up table and used as reference data in advance, then by comparing with this reference data, the type of the "foreign matter / defect" can be distinguished.

[0135] So far, the object to be inspected has been described by limiting it to the light-scattering and transmissive medium, but the present invention can also be applied to the reflective medium. Figure 9A Examples are shown. It should be noted that in Figure 9A and the following Figure 9B , a part of the light guide unit 32 is omitted for simplicity of explanation.Figure 9A This is a schematic diagram showing a reflective embodiment, representing its cross-section with respect to the longitudinal direction of the measurement system. 91 is an inspection object such as an electronic substrate, paper, or film. Light emitted from a light source 92 such as an LED or LD is collimated by a collimating lens 94 such as a refractive index distribution lens or a spherical lens and irradiated onto the inspection object 91. The light receiving optical system arranges lenses typified by a refractive index distribution lens in an array and is configured such that the incident light beam and the reflected light form a wrap angle. A light receiving element array (photodiode array) 96 is arranged at the focal position on the light receiving element side of the light receiving lens array 95.

[0136] In the inspection, information of the inspection object 91 as a reference is acquired in advance, and then the inspection of the product is carried out. The information of the inspection object 91 as a reference is stored in a memory in advance. When the inspection of the product flowing in the process is carried out, it is compared with the pre-stored reference information (implementation of verification). In addition, an asterisk 98 indicates the situation where "foreign matter / defect" adheres to, mixes into, or exists on the inspection object 91. If "foreign matter / defect" exists on the inspection object 91, data different from the reference data is acquired, the difference from the acquired data is calculated, and it is determined that "foreign matter / defect" exists on the inspection object 91 and removed from the process. In addition, Figure 9A in 90Mf, the situation where the component 97 is missing is indicated by a dashed line. If the component indicated by the dashed line is missing, data different from the reference data is acquired in the same way as above, and thus, based on the difference, it is determined that the component is missing and removed from the process. Further, even in the case of a fine wiring break on or inside the electronic substrate, it is similarly detected as "foreign matter / defect".

[0137] Further, even when there are protrusions on the electronic substrate and the "foreign matter / defect" is blocked by the shadow of the protrusions, it can be detected by irradiating the incident light beam symmetrically from both sides at a symmetric angle and symmetrically arranging the light receiving optical system as a wrap angle. In addition, Figure 9A shows the situation where the incident light beam is obliquely incident on the substrate, but it can also be vertically incident as shown in Figure 9B and the light is received obliquely with respect to the substrate. In the reflective type, the light receiving angle considering N.A. is configured to avoid receiving specularly reflected light. In short, the configuration of the measurement system can be changed according to the inspection object.

[0138] The method of the present invention is also effective when the inspection object is a printed matter, a functional film, etc. That is, in a transmissive film, inspections such as the presence or absence of scratches, and for opaque printed matters such as paper, the reflective type is used, and it is effective for inspections of not only scratches but also printing defects, etc. Moreover, in the present invention, even in places where the handling system has vertical movement, it can be used because the depth of field is deep, and the applicable range is expanded.

[0139] In addition, in a light-scattering transmissive medium, particularly in a medium with low transmittance, it is sometimes preferable to reduce the above-mentioned light beam. In this case, the aperture angle of the light beam is determined in consideration of the light-receiving solid angle of the light-receiving element. Further, in the case where the transmittance of the light-scattering transmissive medium is high or the reflectance of the reflective medium is high, when the light beam is expanded to some extent, there is also an effect of reducing the light received by the light-receiving solid angle of the light-receiving element from becoming background noise. Therefore, according to the transmittance and reflectance of the object to be inspected, by conducting research on methods such as collimating the light beam, reducing the light beam, and expanding the light beam, the S / N of the signal can be further improved. In addition, "reducing or expanding the light beam" means further reducing or expanding the collimated parallel light beam. Although the above specific description is omitted, simply put, in the case of a light-scattering transmissive medium, if it is assumed that the light-receiving solid angle hardly changes in the depth direction, the direct incidence of the collimated parallel light beam into the light-receiving element can be suppressed. In the case where the reflective medium is the object to be inspected and the light beam is expanded on the inspection surface of the object to be inspected, the incidence intensity of the direct illumination light beam at the light-receiving solid angle can be reduced, and the S / N of the signal based on the light received by the light-receiving element can be improved. It should be noted that the inspection surface of the object to be inspected refers to the surface where the light beam enters the object to be inspected, and is not limited to one, and may also be a structure in which the light beam enters multiple inspection surfaces.

[0140] Currently, typified by LED printers, the high density of LEDs has been continuously developed, and 1200 dpi has been achieved. If this LED array is used, high resolution can be achieved. That is, as long as the emitted light emitted from the LED array is collimated and the collimated light beam is replaced with Figure 3A a light source for use. In the case of an LED printer, the refractive index distribution lens array is an equal-magnification imaging system of the refractive index distribution type lens, but the refractive index distribution type lens used in the present invention uses a lens having a focal point at infinity. If LD can be arranged at a high density in the future, it is more preferable to use a high-output LD array. Alternatively, it may also be a linear light source in which semiconductor lasers typified by VCSEL (vertical cavity surface emitting laser) are arranged on a plane, arranged in a region. The linear light source is arranged in multiple rows, and further, the inspection accuracy can be improved by inspection based on multiple wavelengths.

[0141] Utilize Figures 3A - 3EThe above method is described again. 31 is an LED or LD array serving as a light source. 32a is a collimating lens array. 34 is an inspection object, and 35 is a "foreign matter / defect" in the inspection object. 37 is a light receiving lens array. 38 is a light receiving element array (photodiode array). In addition, 30 is a light beam emitted from the light source 31, and 33 is a light beam emitted from the collimating lens 32. The light beam 33 is incident on the inspection object 34, and then is incident on the "foreign matter / defect" 35. The light beam 33 incident on the "foreign matter / defect" 35 is scattered by the "foreign matter / defect" 35 to become scattered light 36, which is incident on the light receiving lens array 37, and then is incident on the light receiving element array 38.

[0142] Next, a schematic diagram showing that the collimated light beam enters the light receiving lens array 42, diffuses after exiting, and becomes background noise on the light receiving elements PD1 and PD2 is used. Figure 4B ,right Figure 4B A more excellent method for removing the background noise will be described below.

[0143] exist Figure 4B In the light receiving optical system, the background noise cannot be completely removed and can only be suppressed to a certain extent. In order to further remove it and only turn it into the required net signal component, additional work is needed. The following is a record of its research. The biggest disadvantage of the compound eye lens is that since it is a compound eye lens, the crosstalk component from the adjacent compound eye lens is quite large, and the background noise component expands on the element surface of the light receiving element array (photodiode array) 43. Since attenuation is performed to produce the expansion of the light beam, the crosstalk component becomes smaller. However, there is still room for improvement, and the S / N can be further improved by further reducing the background noise. Figure 10 A schematic diagram showing this method. Figure 10 This is a method in which apertures (arrays) are provided that correspond one by one to the fly-eye lenses of the light receiving system.

[0144] Figure 10 101 is a diagram of an aperture corresponding one-to-one to a compound eye lens of a light receiving system observed from the optical axis direction. 102 represents a hypothetical cross section of the aperture. At the same time, each aperture 101 is roughly consistent with or smaller than the NA of each light source, collimating lens (including a focusing lens forming a beam waist as appropriate), light receiving lens, and light receiving lens on the optical axis of the light receiving element. Alternatively, an aperture may be arranged on the imaging surface of the light receiving lens at one time so that the expanded light is received one-to-one. In this case, the one-to-one correspondence is pre-corrected, and only the signal from a pixel unit that performs the one-to-one correspondence is output.

[0145] Figure 11 is a schematic diagram showing the overlapping of adjacent light beams after collimation. Figure 11As shown, the collimated beam can also be larger than the effective diameter of the fly-eye lens of the light-receiving system. By increasing the size, it is possible to detect foreign objects / defects in the inspection object without missing them. 103 is the part where the collimated beams overlap, and 104 is the non-overlapping part. The "foreign object / defect" 105 is irradiated on this overlapping beam of the adjacent collimated beams, and the "foreign object / defect" 106 is irradiated on the non-overlapping beam. As a result, it is possible to detect "foreign objects / defects" at all positions.

[0146] Using the above Figures 3A - 3E An example of an embodiment of the present invention will be described in detail. The light source 31 is easily arrayed and matrixed, and a VCSEL (Vertical Cavity Surface Emitting Laser) with a large diopter is preferably used. Alternatively, it may be an LED array used in an LED printer. The above VCSELs are densely arranged in a line to determine the pitch of the light source 31. For example, it matches 600 dpi and 1200 dpi. However, it is not limited to this when used other than when processed as an image. Next, the VCSEL array is arranged in parallel with the refractive index distribution type lens array. Since the refractive index distribution type lens array is used as a collimator, a pitch near 1 / 4 pitch is used. Alternatively, it may be 3 / 4 and the pitch nearby. That is, the pitch may be determined so that it can be emitted as a collimated beam. In addition, in addition to the refractive index distribution type lens, a microlens array in which spherical lenses are made small may also be used. In this case, the microlenses are arranged in alignment with the optical axis of the light source 31. When it becomes a collimated beam, there is a beam waist on the emission surface of the VCSEL, and collimation is performed so that this beam waist coincides with the focal point of the collimating lens 32d.

[0147] In the present invention, a laser having a wavelength suitable for the light-scattering transmission medium is used. Particularly in the case of food-related, considering the absorption of moisture, a wavelength in the vicinity of λ = 800 nm to 900 nm is used. There are also media with low transmittance in the above wavelength band for foods (such as confectionery represented by cocoa), and in this case, a wavelength used in optical communication near λ = 1500 nm is sometimes used. There are also wavelength regions with high transmittance for materials containing a large amount of substances such as H2O, CO2, and O2, so the wavelength can be selected as needed to illuminate the inspection object. In addition, when a wavelength is selected, a light-receiving element having a sensitivity range in the selected wavelength is used. For rolls of paper, rolls of film, paper, resin film, metal film, etc. other than food, wavelengths in the visible region can also be used.

[0148] In this embodiment, λ = 830 nm in the near-infrared region is used. At this wavelength, the thickness of the light-scattering and transmissive medium is 10 mm. If a beam waist is set at the central part of the light-scattering and transmissive medium, it is preferable to suppress the change in the beam diameter to about 5% at a distance of ±5 mm. For example, when the size of the light-emitting aperture of the VCSEL is 10 μm in diameter, according to Equation 1, assuming the focal length of the SELFOC lens array is f, when f = 2 mm, the collimated beam diameter d is d = 210 μm.

[0149] W0 = {4·f·λ / (π·d)} / 2…(Equation 1)

[0150] Wherein,

[0151] f: Focal length of the lens,

[0152] λ: Wavelength of the laser beam,

[0153] d: Beam diameter.

[0154] In addition, it can also be a method of focusing the focal point on the central part of the light-scattering and transmissive medium. That is, the beam waist length can be adjusted so as to be a substantially parallel beam in the light-scattering and transmissive medium. In this case, the beam diameter at the beam waist position is obtained using Equation 2 of Kogelnik. However, in the light-scattering and transmissive medium, since the refractive index in air (vacuum) is different, it is also necessary to consider the movement of the beam waist position to determine the beam waist position, and the details will be described later. Equation 2 of Kogelnik representing the propagation of the laser beam is used when determining the allowable radius range of the beam.

[0155] W 2 (z) = W0 2 [1 + {λ·z / (π·W0 2 )} 2 …(Equation 2)

[0156] Wherein,

[0157] W(z): Beam radius at an arbitrary position on the optical axis direction,

[0158] W0: Beam waist radius.

[0159] Since the beam waist radius W0 is obtained by Equation 1, for example, the range of the beam diameter with an error of 5% can be determined by Equation 2. The result of Equation 2 is 217 μm, which can be set as the allowable range.

[0160] The position of the beam waist in air (vacuum) is determined by Equation 1. However, in a light-scattering transmission medium, the refractive index is larger than that in air (vacuum), so the actual position of the beam waist is away from the light source side. Also, corresponding to the shallowing of the convergence angle, the beam waist diameter also changes. The moving distance Δf of the beam waist can be expressed by Equation 3. That is, it can be determined by the focal length of the condenser lens when the laser beam is incident on the incident end face and the beam diameter of the collimated beam. Since it is the distance of the beam near the diffraction limit that does not need to be considered, θ’ approximately applies geometric optics and is obtained by Snell’ Law.

[0161] Δf = tanθ′ / di…(Equation 3)

[0162] Where,

[0163] θ: The maximum value of the incident angle,

[0164] θ’: The maximum value of the refraction angle,

[0165] di: The beam radius incident on the incident end face of the light-scattering transmission medium.

[0166] In a light-scattering transmission medium, Kogelnik's formula cannot be applied, so it is necessary to re-calculate the beam waist diameter. Since the convergence angle near the beam waist does not need to be used, the refraction angle obtained by Snell’ Law approximated by geometric optics is used. The divergence angle Φ of the beam can be expressed by Equation 4 representing the diffraction limit.

[0167] Φ = 2λ / (π·dms)…(Equation 4)

[0168] Where,

[0169] λ’: The wavelength in the light-scattering transmission medium,

[0170] dms: The beam waist diameter in the light-scattering transmission medium,

[0171] λ’: N·λ (λ: The refractive index in air (vacuum)).

[0172] Based on the above, the beam waist diameter dms in the light-scattering transmissive medium is a long focal point where the focal length and the W.D. are approximately equal. For a condenser lens with a small N.A. (Numerical Aperture) of f = 50 mm, when this condenser lens is arranged on the rear side of the collimator lens and on the light source side of the light-scattering transmissive medium, if the diameter of the incident beam to the condenser lens is set to 210 μm, the beam waist diameter 2W0 without the light-scattering transmissive medium is 252 μm. Moreover, it is known that the focal point movement distance in the light-scattering transmissive medium when using a lens with the above focal length is 21 mm. Therefore, when the beam waist position is arranged at the center, it is only necessary to lower the illumination optical system by 16 mm from the light-scattering transmissive medium. Additionally, at this time, according to Equation 4, the beam diameter dms is 377 μm. Based on the above, it is only necessary to determine the position of the optical system according to the thickness and refractive index of the object to be inspected. Additionally, the optical system can also be configured to be movable in the optical axis direction in this way.

[0173] Figure 12A Schematic diagram of the experiment of the edge method showing an embodiment of the present invention Figures 14A - 14D Showing the measured results. Figure 12B Schematic diagram of the experiment of the edge method of the prior art Figures 15A - 15D Showing the measured results of the prior art. It should be noted that in Figure 12A and the following Figure 12B , a part of the light guide unit 32 is omitted for simplicity of explanation. In Figure 12A and Figure 12B , 34a is a diffusion plate. Figure 14A Showing the case of two diffusion plates Figure 14B Showing the case of three diffusion plates Figure 14C Showing the case of four diffusion plates Figure 14D Showing the case of five diffusion plates (standard value). Figure 15A Showing the case of two diffusion plates Figure 15B Showing the case of three diffusion plates Figure 15C Showing the case of four diffusion plates Figure 15D Showing the case of five diffusion plates (standard value). In order to verify the performance of the present invention in place of "foreign matter / defect", the edge was used as the measurement object, and the rising characteristics of the edge signal were observed. Additionally, the light-scattering transmissive medium was set to a diffusion plate Kuraray Komoglass 432L (thickness: t = 2 mm, total light transmittance: 61%, haze: 95%). In order to confirm / verify the thickness non-uniformity, the number of sheets was set to two, three, four, and five, and the maximum thickness was set to 10 mm. Figure 14A (1), Figure 14B (1), Figure 14C (1), Figure 14D(1) Results of diffusion plates for each number of sheets. As a comparative example, Figure 15A (1), Figure 15B (1), Figure 15C (1), Figure 15D (1) represents the rising characteristics of the edge signal of the existing method. The light source uses the light beam after collimating the LD (Panasonic LNCT28PS01WW). Figure 13 Represents the beam profile of the semiconductor laser in the object to be inspected. To be regarded as an array, one LD is moved at each pixel pitch, and the signals corresponding to the one-to-one pixels are obtained successively.

[0174] Figure 14A (1), Figure 14B (1), Figure 14C (1), Figure 14D (1) is a graph showing the above-mentioned edge response (relative intensity) in an example of an embodiment of the present invention. The pixel size is approximately 62 μm in the main scanning direction. In addition, Figure 14A (2), Figure 14B (2), Figure 14C (2), Figure 14D (2) takes the difference (relative intensity) of the outputs from adjacent pixels. From Figure 14A (2), Figure 14B (2), Figure 14C (2), Figure 14D (2), it can be seen that there is a clear difference between adjacent pixels, and the difference in relative intensity is 10% of the peak. Therefore, it can be seen that discrimination for each pixel (equivalent to 400 dpi) can be performed. Further, if the size of the element is reduced, the pixel size and pitch are reduced, the pixel size and pitch are shrunk, resolutions of 600 dpi, 1200 dpi, and further resolutions above them can be achieved. The size (pixel size) of the light-receiving element is preferably set to satisfy 200 dpi or more.

[0175] Figures 15A - 15D Shows the edge response (relative intensity) according to the prior art as a comparative example. There are clear differences between the present invention and the prior art. It can be seen that in the prior art, there is no pixel resolution in any of the diffusion plates, and the graph showing the difference has been buried in the background noise (random noise) and foreign object detection cannot be performed. In contrast, it can be seen that the present invention can perform foreign object detection regardless of the thickness of any of the diffusion plates.

[0176] Next, the results of the response of the light-receiving sensor when there is a "foreign object / defect" in the light-scattering transmissive medium with a thickness (t = 30 mm) in the optical axis direction obtained by the simulation model are shown. The schematic diagram of the model is as Figure 16 shown. It should be noted that in Figure 16In [the description], a part of the light guide unit 32 is omitted for simplicity of explanation. PMMA is selected as the object to be inspected, and silicone spherical particles with a particle size of 2 μm are used as the light scattering particles. The concentration varies between 0.04 wt% and 0.20 wt%. The light source is collimated and has a cross-sectional size of 150 μm, which is larger than the light receiving element (main scanning direction size: 62 μm). Figures 17A - 17F is a graph showing the simulation results, Figures 17A - 17F is a graph representing the simulation results. The foreign object is a sphere with a diameter of 100 μm and is an absorber with an interface having a transmittance of 0%. In addition, the foreign object particle is located at the center of the object to be inspected. Figure 17A represents the case where the concentration of the scattering particles is 0.00 wt%, Figure 17B represents the case where the concentration of the scattering particles is 0.04 wt%, Figure 17C represents the case where the concentration of the scattering particles is 0.08 wt%, Figure 17D represents the case where the concentration of the scattering particles is 0.12 wt%, Figure 17E represents the case where the concentration of the scattering particles is 0.16 wt%, Figure 17F represents the output comparison at each concentration.

[0177] In addition, in Figures 18A - 18F , Figures 19A - 19F a graph showing the simulation results of foreign object particles located at positions deviated by ±14.5 mm from the center of the object to be inspected is shown. That is, the foreign object particle is located at a depth of 0.5 mm from the end of the object to be inspected. Figures 18A - 18F represents the case where the foreign object particle is located at the light source side end of the object to be inspected, Figures 19A - 19F represents the case where the foreign object particle is located at the light receiving element side end of the object to be inspected. From this simulation result, it can be seen that both are responses very similar to the case of foreign object particles in the central part of the light scattering transmissive medium, well representing the effect of the present invention and being very excellent in the suitability for detecting "foreign objects / defects" in the light scattering transmissive medium with thickness.

[0178] As described above, it can be seen that the present invention has excellent detection accuracy for "foreign objects / defects" in the light diffusion transmissive medium compared to the prior art. In addition, the method of the present invention can also be applied to the detection of "foreign objects / defects" in the reflective medium. Further, an image can be generated based on the received light signal from the light scattering transmissive medium, and further analysis of non-conforming products removed according to the level of the detection signal can be performed. In this case, it is assumed that off-line inspection is mainly carried out rather than on-line inspection, but by increasing the signal processing speed, on-line analysis can also be automatically performed. In this way, inspections that cannot be applied in the prior art can be carried out, the quality of the inspection is further improved, and further improvement in the quality of the product to be inspected can be achieved.

[0179] <Effect and Advantage>

[0180] As described above, by using a collimated parallel beam with a small enough diameter, or by adjusting the beam waist in the object to be inspected for light scattering transmissivity to be a substantially parallel beam, and further, according to the object to be inspected, adjusting the beam convergence angle and divergence angle, it is possible to suppress the overlap of the spread of light caused by light scattering (diffusion). In addition, by using a light receiving element in units of one pixel corresponding one-to-one between each irradiation position and the light source, and selecting the output signal from the pixel in such a way as to receive only the signal near the optical axis of the beam, it is possible to suppress crosstalk between pixels, and to separately detect the light that is the cause of the background noise caused by scattered light (diffused light), directly incident light, etc. and the change in the amount of light caused by "foreign matter / defect". Therefore, it is possible to clarify the "foreign matter / defect" object in the object to be inspected and to perform accurate inspection. In addition, by the light guiding unit, high-resolution detection can be performed. Further, in the case of having a light receiving system that expands the beam interval reduced once, it is possible to maintain the resolution for "foreign matter / defect" in the object to be inspected, and to unify the interval of the light receiving elements. Therefore, it is also possible to achieve a cost reduction effect and to improve the S / N by increasing the size of the light receiving element.

[0181] Description of Reference Numerals

[0182] 10: Linear illumination light source;

[0183] 11: Lens array;

[0184] 12: Light receiving part;

[0185] 31: Light source;

[0186] 32: Light guiding element;

[0187] 32a: Collimating lens array;

[0188] 32b: Optical fiber array;

[0189] 32c: Lens array;

[0190] 32d: Collimating lens;

[0191] 32e: Optical fiber;

[0192] 32f: Lens;

[0193] 32g, 32h, 32i, 32k: Combined lens;

[0194] 33: Beam;

[0195] 34: Object to be inspected;

[0196] 36: Scattered light;

[0197] 37: Light-receiving lens array;

[0198] 38: Light-receiving element array;

[0199] 39: Focus position;

[0200] 42: Light-receiving lens array;

[0201] 45: Light beam;

[0202] 74: Light-receiving lens array;

[0203] 76: Object to be inspected;

[0204] 77: Pixel;

[0205] 91: Object to be inspected;

[0206] 92: Light source;

[0207] 94: Collimating lens;

[0208] 95: Light-receiving lens array.

Claims

1. A foreign object / defect inspection device, characterized in that, the foreign object / defect inspection device comprises: an illumination optical system including an optical scanning unit that scans a light beam obtained by collimating light emitted from a plurality of linearly spaced-apart light sources toward at least one inspection surface of an inspection object having light scattering properties, or a light beam obtained by further substantially condensing the collimated light beam; a light receiving optical system arranged in parallel with the scanning direction of the illumination optical system in such a way that the light sources and one pixel unit composed of at least one light receiving element correspond one-to-one. The light receiving optical system includes a plurality of light receiving elements. After the light beam passes through the inspection surface of the inspection object, the light beam irradiates a foreign object or defect in the inspection object, and the plurality of light receiving elements receive scattered light, diffused light, or light with different intensities that is absorbed / diffused and reflected or transmitted and diffused from the foreign object or defect; and a detection unit that detects the light beam of the light source at an arbitrary position in the main scanning direction of the illumination optical system only by using the corresponding light receiving element, the spatial resolution of one pixel unit composed of the at least one light receiving element is equal to or higher than the spatial resolution of the light beam formed by the illumination optical system on the inspection surface of the inspection object, the illumination optical system includes a light guide unit that reduces the interval between the optical axes of the light beams emitted from the plurality of light sources in the arrangement direction of the plurality of light sources and guides the light beams to the inspection object.

2. The foreign object / defect inspection device according to claim 1, characterized in that, the size of the collimated light beam or the light beam obtained by further substantially condensing the collimated light beam is 10 μm or more and 1000 μm or less, and the size of the light receiving element satisfies 200 dpi or more.

3. The foreign object / defect inspection device according to claim 1, characterized in that, the light source of the illumination optical system is a light source composed of at least one LD, and is capable of scanning a light beam obtained by collimating the laser light emitted from the light source or a light beam obtained by further substantially condensing the collimated light beam along the arrangement direction of the plurality of light receiving elements on the inspection surface of the inspection object.

4. The foreign object / defect inspection device according to claim 1, characterized in that, the light source of the illumination optical system is a light source composed of at least one LED, and is capable of scanning a light beam obtained by collimating the laser light emitted from the light source or a light beam obtained by further substantially condensing the collimated light beam along the arrangement direction of the plurality of light receiving elements on the inspection surface of the inspection object.

5. A foreign object / defect inspection device, characterized in that, the foreign object / defect inspection device comprises: an illumination optical system including an optical scanning unit that scans a light beam obtained by adjusting the light emitted from a plurality of linearly spaced-apart light sources toward at least one inspection surface of an inspection object having light scattering properties in a converging manner or in an expanding manner; A light-receiving optical system is arranged parallel to the scanning direction of the illumination optical system in a one-to-one correspondence between the light source and a pixel unit composed of at least one light-receiving element. The light-receiving optical system includes a plurality of light-receiving elements. After the light beam passes through the inspection surface of the inspection object, it irradiates foreign matters or defects located on the inspection object. The plurality of light-receiving elements receive scattered light, diffused light, or light with different intensities that is absorbed / diffused and reflected or transmitted and diffused from the foreign matters or defects. And A detection unit that uses only the corresponding light-receiving element to detect the light beam of the light source at any position in the main scanning direction of the illumination optical system. The spatial resolution of a pixel unit composed of the at least one light-receiving element is higher than the spatial resolution of the light beam formed by the illumination optical system on the inspection surface of the inspection object. The illumination optical system includes a light guide unit that reduces the interval between the optical axes of the light beams emitted from the plurality of light sources in the arrangement direction of the plurality of light sources and guides each light beam to the inspection object.

6. The foreign matter / defect inspection device according to claim 1 or 5, characterized in that the light guide unit includes an optical fiber array having a plurality of optical fibers into which the light beams emitted from the plurality of light sources are incident, and the interval between the emission ends of the optical fibers is smaller than the interval between the incident ends of the optical fibers.

7. The foreign matter / defect inspection device according to claim 6, characterized in that the light guide unit includes a plurality of collimating lenses that are in one-to-one correspondence with the emission ends of the optical fibers and collimate the emitted light from the optical fibers, and the plurality of collimating lenses are arranged in the same number as the plurality of light sources, and their arrangement direction is the same as the arrangement direction of the light-receiving elements.

8. The foreign matter / defect inspection device according to claim 6, characterized in that the light guide unit includes a reduction combination lens composed of a combination of a plurality of lenses arranged between the optical fiber array and the inspection object, and the interval between the optical axes of the light beams emitted through the reduction combination lens is smaller than the interval between the optical axes of the light beams incident on the reduction combination lens.

9. The foreign matter / defect inspection device according to claim 1 or 5, characterized in that the light guide unit includes a reduction combination lens composed of a combination of a plurality of lenses arranged between the plurality of light sources and the inspection object, and the interval between the optical axes of the light beams emitted through the reduction combination lens is smaller than the interval between the optical axes of the light beams incident on the reduction combination lens.

10. The foreign matter / defect inspection device according to claim 8, characterized in that the light-receiving optical system includes an enlargement combination lens composed of a combination of a plurality of lenses arranged between the inspection object and the plurality of light-receiving elements, and the interval between the optical axes of the light beams emitted through the enlargement combination lens is larger than the interval between the optical axes of the light beams incident on the enlargement combination lens.

11. The foreign matter / defect inspection device according to claim 10, characterized in that The magnifying combined lens has a magnification factor that magnifies the interval between the optical axes of the respective light beams emitted through the magnifying combined lens in a manner that matches the interval of the light receiving elements.

12. The foreign matter / defect inspection apparatus according to claim 8, wherein: Each of the plurality of lenses has a diopter represented by the reciprocal of the focal length in the arrangement direction of the plurality of light sources, and the combined lens is constituted by a combination of lenses having different diopters.

13. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The scanning interval of the light beams of the illumination optical system is equal to or less than the spatial resolution of pixel units constituted by at least one light receiving element arranged along the main scanning direction.

14. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The object to be inspected is a medium having the property of transmitting the light emitted from the light source.

15. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The object to be inspected is a medium having the property of reflecting the light emitted from the light source.

16. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The light receiving optical system has a lens system that forms an image of the light transmitted through the inspection surface of the object to be inspected on the light receiving elements.

17. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The detection unit synchronizes with the scanning of the light beams in the illumination optical system and outputs signals only from the light receiving elements near the center of the light beams at each scanning position among the plurality of light receiving elements.

18. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The foreign matter / defect inspection apparatus has a plurality of combinations of the light source and at least one light receiving element of one pixel unit on one inspection surface of the object to be inspected.

19. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The combination of the illumination optical system and the light receiving optical system is movable in the optical axis direction.

20. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The light receiving element is a line sensor.

21. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The light receiving element is an area sensor.

22. The foreign matter / defect inspection apparatus according to claim 1 or 5, wherein: The light receiving optical system includes a lens array.

23. The foreign matter / defect inspection apparatus according to claim 22, wherein: The lens array includes compound eye lenses corresponding one-to-one to the respective pixels, and an aperture corresponding one-to-one to each pixel is provided between the compound eye lens and each pixel, and each aperture is located on the optical axis of each light source.

24. The foreign matter / defect inspection apparatus according to claim 16, wherein: The aperture angle of the lens system is 1 mrad to 20 mrad with respect to the incident angle of scattered light, diffused light generated by light scattering in the light transmitted through the inspection surface, or light with intensity that has been absorption / diffusion reflected or transmitted and diffused into the lens system.

25. The foreign matter / defect inspection device according to claim 1 or 5, wherein, the foreign matter / defect inspection device has light sources of multiple wavelengths.

26. The foreign matter / defect inspection device according to claim 1 or 5, wherein, the multiple light sources arranged linearly and separated from each other have multiple lines, and are multiple linear light sources of the same wavelength, or multiple linear light sources of different wavelengths.

27. The foreign matter / defect inspection device according to claim 1 or 5, wherein, the foreign matter / defect inspection device has inspection surfaces of multiple inspection objects and has multiple depth-of-field regions in the optical axis direction.

28. A foreign matter / defect inspection method, wherein, the foreign matter / defect inspection method includes: a step of scanning a light beam by an illumination optical system, the illumination optical system including an optical scanning unit that scans a light beam obtained by collimating the light emitted from multiple linearly separated light sources toward at least one inspection surface of an inspection object having light scattering properties, or a light beam obtained by further approximately condensing the collimated light beam; a step of receiving the light beam by a light receiving optical system, the light receiving optical system being arranged in parallel with the scanning direction of the illumination optical system in such a way that the light source and one pixel unit composed of at least one light receiving element correspond one-to-one, the light receiving optical system including multiple light receiving elements, and the light beam transmitted through the inspection surface of the inspection object irradiates a foreign matter or defect in the inspection object, and the multiple light receiving elements receive scattered light, diffused light, or light with intensity that has been absorption / diffusion reflected or transmitted and diffused from the foreign matter or defect; and a step of detecting only by the corresponding light receiving element the light beam of the light source at an arbitrary position in the main scanning direction of the illumination optical system, the spatial resolution of one pixel unit composed of the at least one light receiving element is equal to or higher than the spatial resolution of the light beam formed by the illumination optical system on the inspection surface of the inspection object, the illumination optical system includes a light guiding unit that guides each light beam emitted from the multiple light sources to the inspection object by reducing the interval between the optical axes of the respective light beams in the arrangement direction of the multiple light sources.

29. A foreign matter / defect inspection method, wherein, the foreign matter / defect inspection method includes: a step of scanning a light beam by an illumination optical system, the illumination optical system including an optical scanning unit that scans a light beam adjusted in a manner of converging the light emitted from multiple linearly separated light sources toward at least one inspection surface of an inspection object having light scattering properties, or a light beam adjusted in a manner of expanding. A step of receiving a light beam through a light-receiving optical system, the light-receiving optical system being arranged in parallel with the scanning direction of the illumination optical system in a one-to-one correspondence manner between the light source and a pixel unit composed of at least one light-receiving element, the light-receiving optical system including a plurality of light-receiving elements, the light beam after passing through the inspection surface of the inspection object irradiates a foreign object or defect located in the inspection object, and the plurality of light-receiving elements receive scattered light, diffused light, or light with different intensities that is absorbed / diffused and reflected or transmitted and diffused from the foreign object or defect; and A step of detecting, by using only the corresponding light-receiving element, the light beam of the light source at an arbitrary position in the main scanning direction of the illumination optical system; The spatial resolution of a pixel unit composed of the at least one light-receiving element is equal to or higher than the spatial resolution of the light beam formed by the illumination optical system on the inspection surface of the inspection object; The illumination optical system includes a light guide unit that guides each light beam to the inspection object by reducing the interval between the optical axes of the light beams emitted from the plurality of light sources in the arrangement direction of the plurality of light sources.

30. The foreign object / defect inspection method according to claim 28 or 29, characterized in that the light guide unit includes an optical fiber array having a plurality of optical fibers into which the light beams emitted from the plurality of light sources are incident, and the interval between the emission ends of the optical fibers is smaller than the interval between the incident ends of the optical fibers.

31. The foreign object / defect inspection method according to claim 30, characterized in that the light guide unit includes a plurality of collimating lenses that collimate the emitted light from each optical fiber in a one-to-one correspondence with the emission ends of the optical fibers, the plurality of collimating lenses are arranged in the same number as the plurality of light sources, and their arrangement direction is the same as the arrangement direction of the light-receiving elements.

32. The foreign object / defect inspection method according to claim 31, characterized in that the light guide unit includes a reduction combination lens composed of a combination of a plurality of lenses arranged between the optical fiber array and the inspection object, and the interval between the optical axes of the light beams emitted through the reduction combination lens is smaller than the interval between the optical axes of the light beams incident on the reduction combination lens.

33. The foreign object / defect inspection method according to claim 28 or 29, characterized in that the light guide unit includes a reduction combination lens composed of a combination of a plurality of lenses arranged between the plurality of light sources and the inspection object, and the interval between the optical axes of the light beams emitted through the reduction combination lens is smaller than the interval between the optical axes of the light beams incident on the reduction combination lens.

34. The foreign object / defect inspection method according to claim 32, characterized in that the illumination optical system includes an enlargement combination lens composed of a combination of a plurality of lenses arranged between the inspection object and the plurality of light-receiving elements, and the interval between the optical axes of the light beams emitted through the enlargement combination lens is larger than the interval between the optical axes of the light beams incident on the enlargement combination lens.

35. The foreign object / defect inspection method according to claim 34, characterized in that The magnifying combined lens has a magnification factor that magnifies the interval between the optical axes of the respective light beams emitted through the magnifying combined lens in a manner that matches the interval of the light receiving elements.

36. The foreign matter / defect inspection method according to claim 32, wherein, each of the plurality of lenses has a diopter represented by the reciprocal of the focal length in the arrangement direction of the plurality of light sources, and the combined lens is constituted by a combination of lenses having different diopters.

37. The foreign matter / defect inspection method according to claim 28 or 29, wherein, the scanning interval of the light beams of the illumination optical system is equal to or less than the spatial resolution of a pixel unit constituted by at least one light receiving element arranged in the main scanning direction.

38. The foreign matter / defect inspection method according to claim 28 or 29, wherein, the foreign matter / defect inspection method has light sources of a plurality of wavelengths.

39. The foreign matter / defect inspection method according to claim 28 or 29, wherein, the plurality of light sources arranged linearly and separated from each other have a plurality of lines, and are linear light sources of the same wavelength or linear light sources of different wavelengths.

40. The foreign matter / defect inspection method according to claim 28 or 29, wherein, the foreign matter / defect inspection method has inspection surfaces of a plurality of the inspection objects and has a plurality of depth of field regions in the optical axis direction.

Images