Foreign body / defect inspection device, image generating device for foreign body / defect inspection, and foreign body / defect inspection method

Abstract

To detect a "foreign substance / defect" with a good S / N (with extremely little crosstalk) even in a thick inspection target having a light scattering property.SOLUTION: A light source has a one-to-one correspondence with a pixel unit composed of at least one light receiving element of a light receiving element array (photodiode array), and a light beam is detected by at least one light receiving element (one pixel element) corresponding to the light source only when the light source emits light. An illumination optical system includes light guide means that reduces a distance between optical axes of respective light beams emitted from the plurality of light sources in arrangement directions of the plurality of light sources and guides the light beam to an inspection object.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] The present invention relates to an inspection method and apparatus for detecting foreign bodies in a light scattering transmissive medium and for scratches, irregularities, defects, missing parts, and attached foreign bodies in a thick inspection object, and also to an image generating apparatus for detected foreign bodies. [Background technology]

[0002] Conventionally, systems that have been adopted for surface inspection equipment that mainly uses a light source in the visible range are representative inspection systems that combine a line sensor camera, a contact image sensor (hereinafter referred to as CIS), or a scanning optical system using a laser beam with a light receiving optical system that includes a photoelectric conversion element (photomultiplier, avalanche photodiode, CCD sensor, CMOS sensor, etc.) and a light guide, and most of these are reflective types that receive reflected light or fluorescence from scratches, unevenness, defects, missing parts, and foreign particles attached to the object being inspected.

[0003] On the other hand, in a transmission type where the light receiving system and the illumination system are arranged opposite to each other with the inspection object in between, the inspection object is often transparent, thin, and has a high transmittance. However, there are few systems that can detect foreign objects, scratches, defects, etc. contained in a thick inspection object.

[0004] X-ray inspection equipment, which is renowned as a non-destructive inspection device with excellent transparency, uses X-rays, which are radioactive, so it is necessary to set up a radiation control area and to control the amount of radiation exposure to people. In other words, the hurdle of deciding where to install it is high. Moreover, because it is large and heavy, it is not easy to add it to an existing production line in a factory. In addition, because it is expensive, it is not possible to install many inspection points.

[0005] Furthermore, the excellent transparency of X-rays themselves is a drawback for X-ray inspection equipment, as they can penetrate even foreign objects, defects, and scratches, making it often impossible to distinguish between them.

[0006] In an inspection device using a wavelength other than X-rays, when the transmissive medium has light scattering properties, a device for detecting foreign matter, scratches, defects, missing parts, etc. contained in the transmissive medium has not been realized.

[0007] In the present invention, in addition to technical issues, when considering introduction to the field, ease of installation, danger to the human body, and the cost of installation equipment were also taken into consideration, and it is assumed that a light source other than X-rays will be used.

[0008] Patent Document 1 discloses a means for detecting depressions and folds in a film by scanning a laser beam, which is illumination light, in the main scanning direction.

[0009] In Patent Document 2, the optical axis of the illumination optical system is shifted from the optical axis of the light receiving optical system to prevent the transmitted light of the inspection object from being buried in the direct light from the illumination optical system and disturbance light. That is, Patent Document 2 describes a method of irradiating the inspection object with light and utilizing information contained in the shadow of the transmitted light in order to detect foreign objects and defects inside the inspection object, and in this case, the method is devised to make it easier to detect foreign objects and defects by preventing components such as disturbance light that become noise from being mixed into the signal from foreign objects and defects near the surface of the inspection object.

[0010] Patent Document 3 shows that polarized light is used to acquire multiple images in which the polarization axes on the illumination side and the light receiving side are shifted in different ways, and then by adjusting the contrast and applying processing such as subtraction, noise can be canceled, making it possible to accurately detect foreign objects and defects inside the object being inspected.

[0011] Patent Document 4 shows that a transmission image can be obtained by aligning the optical axes of a laser beam scanning optical system and a light receiving optical system that receives light transmitted through a sample. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2010-271133 A [Patent Document 2] JP 2015-219090 A [Patent Document 3] Patent No. 6451980 [Patent Document 4] Japanese Patent Application Publication No. 3-134609 Summary of the Invention [Problem to be solved by the invention]

[0013] In Patent Document 1, mainly scratches and irregularities on the surface of the inspection object are detected. The inspection objects are often thin materials such as films, and can be inspected with a CIS with a shallow depth of field. However, when the inspection object is a thick object with large surface irregularities or the inspection of wiring patterns such as laminated electronic boards, detection becomes difficult with a conventional CIS with a depth of field of only 1 to 2 mm. A new inspection device equipped with a light receiving optical system with a deep depth of field and a long working distance (hereinafter referred to as WD) is required.

[0014] Optical systems with a deep depth of field are mainly telecentric optical systems, and line sensor cameras equipped with such optical systems are mainstream. However, telecentric optical systems are large in size and difficult to use in narrow conveying paths in factories. Furthermore, when the conveying width of a factory production line is wide, telecentric optical systems require many cameras because the field of view is narrow. Therefore, there is also the drawback of high introduction costs.

[0015] In the case of the optical system of Patent Document 2, when detecting foreign bodies, defects, scratches, etc. in a transmissive medium with high light scattering properties, the amount of light received by the light-receiving optical system is reduced because the light near the optical axis of the illumination optical system is not used. In addition, the transmitted light that can be detected is mainly received as scattered light within the object being inspected, so that the disturbance light scattered by the object being inspected itself becomes the dominant signal component, making it difficult to discriminate and detect the net scattered light scattered by foreign bodies deep within the object being inspected.

[0016] In the case of Patent Document 3, there is no problem if the light scattering property of the sample is small. However, if the light scattering ability of the object to be inspected is large, polarization information is lost due to depolarization caused by scattering, so differences due to the shifting of the polarization axis are difficult to detect, making it difficult to detect foreign objects or defects in the object to be inspected, which is a transparent light scattering medium.

[0017] In the case of Patent Document 4, for a thick inspection target, even if the medium has a high total light transmittance, minute non-uniformities in the refractive index in the medium may cause the optical axes of the laser beam scanning optical system and the light receiving optical system to not coincide, and a signal may not be obtained. In other words, there may be cases where foreign matter, scratches, defects, missing parts, etc. are overlooked.

[0018] As described above, in the conventional technology, since the depth of field is generally shallow, for example, when the object to be inspected is a food inspection object or a circuit board having a thickness of 10 mm or more, information in the depth direction cannot be obtained, and as a result, foreign bodies, defects, scratches, missing parts, etc. cannot be detected. Alternatively, a telecentric optical system with a deep depth of field is large, so it is difficult to arrange it in a narrow space. In addition, for example, when inspecting all foreign bodies on a production line in a factory, the above detection method cannot detect scratches or defective parts on an electronic board, and there is a risk that the presence of foreign bodies will be overlooked and the food will be shipped, especially in the case of food.

[0019] As described above, conventional CIS has a shallow depth of field, and therefore cannot grasp information in the depth direction of thick objects to be inspected, making it impossible to guarantee the reliability of the inspection. In addition, conventional methods other than CIS inevitably require large sizes because they use camera lenses and telecentric optical systems, making it difficult to add them to existing production lines in factories, and especially impossible to add them to narrow spaces.

[0020] A typical CIS is shown in Fig. 1, and a linear illumination optical system for a CIS is similarly shown in Fig. 2. Fig. 1 is a cross-sectional view of the CIS near the center in the longitudinal direction. Fig. 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 a light intensity distribution that is elongated in the main scanning direction.

[0021] In the CIS shown in FIG. 1, two housings 16 are arranged opposite to each other with a focal plane 20 in between. A linear illumination light source 10 for illuminating an object to be inspected on the focal plane 20 is provided in each housing 16. A lens array 11 and a light receiving unit 12 are provided in one housing 16, and light from the illuminated object to be inspected is guided to the light receiving unit 12 by the lens array 11. The lens array 11 is an optical element that forms an image of the light from the object to be inspected on the light receiving unit 12. In the CIS shown in FIG. 1, one of the two linear illumination light sources 10 is arranged on the light receiving unit 12 side and the other is arranged on the opposite side to the light receiving unit 12 side with respect to the focal plane 20.

[0022] The light receiving unit 12 is mounted on a substrate 13 fixed to one of the housings 16. The light that has passed through the lens array 11 is received by a light receiving surface 12A of the light receiving unit 12, and a signal according to the amount of received light is output from the light receiving unit 12. As the inspection object is transported in one direction X along the focal plane 20, the light from the inspection object is continuously received by the light receiving unit 12, and an image of the inspection object (such as a color image or a fluorescent image) is obtained based on the output signal from the light receiving unit 12.

[0023] Light B3 emitted from one of the linear illumination light sources 10 passes through a protective glass 14 fixed to a housing 16, is reflected by a reflecting member 17A provided on the inner surface of a protective glass 14A fixed to the other housing 16, and is guided to a focal plane 20. An ultraviolet light blocking filter (UV cut filter) 15 that blocks ultraviolet light from entering the light receiving unit 12 is provided at an arbitrary position between the focal plane 20 and the light receiving unit 12. In addition, a color filter 18 that passes visible light in a specific wavelength range is provided between the light receiving unit 12 and the ultraviolet light blocking filter 15. A substrate 5 for fixing a light source unit 103 (such as an ultraviolet light source or a visible light source) provided in the linear illumination light source 10 is provided at a position facing the bottom surface of the linear illumination light source 10 in one of the housings 16.

[0024] The linear illumination light source 10 includes a transparent light guide 101 extending along the longitudinal direction L, a light source unit 103 provided near one end face in the longitudinal direction L, and a cover member 102 for holding each side face of the light guide 101. The light emitted from the light source unit 103 enters the light guide 101, and while propagating through the light guide 101, is appropriately reflected by the light diffusion pattern P, and is emitted from the light emission surface in the direction of the arrow, becoming a linear illumination light to illuminate the inspection object. However, in the illumination optical system, the illumination light is diffused by the light guide 101, and in an inspection object having a thickness and light scattering transparency, attenuation of the amount of received light in the optical axis direction becomes a problem. Furthermore, the depth of field of the conventional CIS is shallow, and when the inspection object has a thickness, it is difficult to inspect the entire thickness direction, and since the WD is narrow, the inspection object is often contacted and the inspection itself is not performed. That is, with conventional CIS optical systems, it is extremely difficult to inspect a thick transmissive medium for foreign particles or defects, and it is even more difficult when the medium has light scattering properties. [Means for solving the problem]

[0025] The inventors of the present application have conducted extensive research into the above problems and have found a means for detecting foreign bodies, defects, scratches, and defects even in an inspection target made of a light scattering medium having a thickness of 10 mm or more, and for realizing a thin and compact CIS like the conventional CIS. They have also found that it is possible to detect foreign bodies and defects in an inspection target even if the inspection target is a thick transmissive medium with a larger light scattering ability. Specifically, the inventors of the present application have provided a method for preventing the light beam and scattered light from foreign bodies and defects irradiated by the light beam from being incident on pixels that are not irradiated with the light beam, and at the same time, for extracting an output signal only from at least one light receiving element in one pixel unit that has a one-to-one correspondence with the light source, thereby minimizing crosstalk components between pixels and enabling accurate detection of foreign bodies and defects in an inspection target. When at least one light receiving element of the light receiving optical system is regarded as a unit pixel, if the unit pixel is switched to output only during the dwell time of one pixel in the light beam scanning, which is the optical scanning illumination light passing through the pixel, and the light beam or the scattered light from the foreign matter or defect irradiated by the light beam is not incident on the pixel that is not irradiated with the light beam, it is possible to minimize the crosstalk component between pixels and accurately detect the foreign matter or defect in the inspection object. Here, the dwell time means the period during which the approximate center of the light beam crosses from one end to the other end of the one pixel. If the diameter of the irradiation light beam of the illumination optical system is made approximately the same in the depth direction of the inspection object and is smaller than the pixel resolution of the light receiving optical system, the foreign matter, defect, scratch, missing part, etc. in the inspection object can be illuminated approximately uniformly. In the present invention, in addition to the above-mentioned one-to-one correspondence arrangement of light sources and light receiving elements and the relationship between illumination and light receiving element output, a method is proposed that enables detection with even higher resolution. Specifically, the illumination optical system includes a light guiding means that reduces the interval between the optical axes of each light beam emitted from the multiple light sources in the arrangement direction of the multiple light sources and guides them to the inspection object. In addition, the illumination optical system may include a means for expanding the interval between the optical axes of each light beam emitted from the multiple light sources, which has been reduced once, to match the light receiving element. Effect of the Invention

[0026] According to the present invention, one pixel unit consisting 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, a light beam is detected by at least one light receiving element (one pixel unit) corresponding to the light source. Therefore, only one light beam that is collimated or further approximately focused is incident on a "foreign substance / defect" in an inspection object, and the light receiving element can separate and detect only the scattered light, so that even if the inspection object has light scattering properties and is thick, it is possible to detect "foreign substances / defects" with a good S / N ratio (very little crosstalk). In addition, the light guiding means enables high-resolution detection. In the present invention, the inspection object having light scattering properties includes not only light scattering transparent media but also reflective media. In the present invention, the depth of field on the light source side is deep, making it possible to inspect for "foreign bodies and defects" even if the object being inspected is a reflective medium, and also enabling high-resolution inspection even if a thin object being inspected, such as film, moves in the optical axis direction in a location where the process transport system moves violently up and down. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a cross-sectional view of a conventional CIS. [Diagram 2] FIG. 1 is an exploded perspective view of a conventional linear illumination optical system for a CIS. [Figure 3A] 1 is a schematic diagram of a foreign matter / defect inspection device according to the present invention. [Figure 3B] FIG. 13 is a schematic diagram showing a first modified example of the foreign matter / defect inspection apparatus. [Figure 3C] FIG. 13 is a schematic diagram showing a second modified example of the foreign matter / defect inspection apparatus. [Figure 3D] FIG. 13 is a schematic diagram showing a third modified example of the foreign matter / defect inspection apparatus. [Figure 3E] FIG. 13 is a schematic diagram showing a fourth modified example of the foreign matter / defect inspection apparatus. [Figure 4A] FIG. 13 is a diagram illustrating crosstalk of scattered light to adjacent pixels according to the present invention. [Figure 4B] 1 is a diagram showing how a parallel light beam according to the present invention enters a light-receiving lens array, spreads after exiting, and becomes background noise on a light-receiving element. [Figure 5A] In the conventional invention, the signal is a mixture of crosstalk components and background noise components. [Figure 5B] In the present invention, this is a signal that contains almost no crosstalk components or background noise components. [Figure 6A] This is a graph showing forward scattering of 10 μm particle size, and shows Mie scattering when the transparent medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6B] This is a graph showing forward scattering of 10 μm particle size, and shows Mie scattering when the transparent medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6C] This is a graph showing forward scattering of 17 μm particle size, and represents Mie scattering when the transmitting medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6D] This is a graph showing forward scattering of 17 μm particle size, and represents Mie scattering when the transmitting medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6E] This is a graph showing forward scattering of 25 μm particle size, and represents Mie scattering when the transmitting medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6F] This is a graph showing forward scattering of 25 μm particle size, and represents Mie scattering when the transmitting medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6G] This is a graph showing forward scattering of 30 μm particle size, and represents Mie scattering when the transparent medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 6H] This is a graph showing forward scattering of 30 μm particle size, and represents Mie scattering when the transparent medium is polycarbonate and the particles are silica (logarithmic scale). [Figure 7] FIG. 1 is a schematic diagram showing a multi-beam illumination-multi-scanning light receiving method according to the present invention. [Figure 8] This represents the scattering of light due to opaque "foreign objects / defects." [Figure 9A]FIG. 2 is a schematic diagram showing a reflective embodiment. [Figure 9B] FIG. 13 is a schematic diagram showing another embodiment of a reflective type of the present invention. [Figure 10] 1 is a schematic diagram of another method of the present invention for further reducing crosstalk components, in which an aperture (array) is provided for each of the multi-lenses in the light receiving system. [Figure 11] FIG. 2 is a schematic diagram showing a case where adjacent collimated light beams overlap each other (a cross-sectional view seen from the optical axis direction). [Figure 12A] FIG. 1 is a schematic diagram of an experiment using the edge method of the present invention. [Figure 12B] FIG. 1 is a schematic diagram of an experiment using the edge method of the prior art. [Figure 13] 1 shows a beam profile of an LD in an embodiment of the present invention. [Figure 14A] In an embodiment of the present invention, (1) a graph showing the response of an edge signal when there are two diffusers (normalized values), and (2) a graph showing the difference between adjacent pixels of the edge response signal (normalized values). [Figure 14B] In an embodiment of the present invention, (1) a graph showing the response of an edge signal when three diffusers are used (normalized values), and (2) a graph showing the difference between adjacent pixels of the edge response signal (normalized values). [Figure 14C] In an embodiment of the present invention, (1) a graph showing the response of an edge signal when four diffusers are used (normalized values), and (2) a graph showing the difference between adjacent pixels of the edge response signal (normalized values). [Figure 14D] In an embodiment of the present invention, (1) a graph showing the response of an edge signal when five diffusers are used (normalized values), and (2) a graph showing the difference between adjacent pixels of the edge response signal (normalized values). [Figure 15A] Graphs showing (1) edge signal response when using two diffusers (normalized values) and (2) the difference between adjacent pixels in edge response signals (normalized values) in the conventional method. [Figure 15B]Graphs showing (1) edge signal response when three diffusers are used (normalized values) and (2) the difference between adjacent pixels in edge response signals (normalized values) in the conventional method. [Figure 15C] Graphs showing (1) edge signal response when four diffusers are used (normalized values) and (2) the difference between adjacent pixels in edge response signals (normalized values) in the conventional method. [Figure 15D] Graphs showing (1) edge signal response when five diffusers are used (normalized values) and (2) the difference between adjacent pixels in edge response signals (normalized values) in the conventional method. [Figure 16] FIG. 2 is a schematic diagram showing a simulation model of the present invention. [Figure 17A] 11 is a graph showing the results of a simulation in which a foreign particle is located at the center of a light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.00 wt %. [Figure 17B] 1 is a graph showing the results of a simulation in which a foreign particle is located at the center of a light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.04 wt %. [Figure 17C] 1 is a graph showing the results of a simulation in which a foreign particle is located at the center of a light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.08 wt %. [Figure 17D] 11 is a graph showing the results of a simulation in which a foreign particle is located at the center of a light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.12 wt %. [Figure 17E] 11 is a graph showing the results of a simulation in which a foreign particle is located at the center of a light-scattering transmissive medium and the scattering particle concentration of the light-scattering transmissive medium is 0.16 wt %. [Figure 17F] 11 is a graph showing the results of a simulation in which a foreign particle is located at the center of a light scattering transmissive medium, and shows a comparison of outputs at various concentrations of the light scattering transmissive medium. [Figure 18A]11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light scattering transmissive medium on the light source side, and the scattering particle concentration of the light scattering transmissive medium is 0.00 wt %. [Figure 18B] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light scattering transmissive medium on the light source side, and the scattering particle concentration of the light scattering transmissive medium is 0.04 wt %. [Figure 18C] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light scattering transmissive medium on the light source side, and the scattering particle concentration of the light scattering transmissive medium is 0.08 wt %. [Figure 18D] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light scattering transmissive medium on the light source side, and the scattering particle concentration of the light scattering transmissive medium is 0.12 wt %. [Figure 18E] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light scattering transmissive medium on the light source side, and the scattering particle concentration of the light scattering transmissive medium is 0.16 wt %. [Figure 18F] 11 is a graph showing the results of a simulation in which a foreign particle is located at the end of a light scattering transmissive medium on the light source side, showing a comparison of outputs at each concentration. [Figure 19A] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light-scattering transmissive medium on the light-receiving sensor side, and the scattering particle concentration of the light-scattering transmissive medium is 0.00 wt %. [Figure 19B] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light-scattering transmissive medium on the light-receiving sensor side, and the scattering particle concentration of the light-scattering transmissive medium is 0.04 wt %. [Figure 19C] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light-scattering transmissive medium on the light-receiving sensor side, and the scattering particle concentration of the light-scattering transmissive medium is 0.08 wt %. [Figure 19D]11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light-scattering transmissive medium on the light-receiving sensor side, and the scattering particle concentration of the light-scattering transmissive medium is 0.12 wt %. [Figure 19E] 11 is a graph showing the results of a simulation in which foreign particles are located at the end of the light-scattering transmissive medium on the light-receiving sensor side, and the scattering particle concentration of the light-scattering transmissive medium is 0.16 wt %. [Figure 19F] 11 is a graph showing the results of a simulation in which a foreign particle is located at the end of a light-scattering transmissive medium on the light-receiving sensor side, and shows a comparison of outputs at various concentrations. [Figure 20] 1 is a schematic diagram showing one-to-one correspondence between a plurality of light sources arranged in the main scanning direction and a plurality of pixels, each of which is made up of at least one light receiving element. [Figure 21] FIG. 1 is a conceptual diagram of an inspection method according to the prior art. [Figure 22] When the object to be inspected is thick and the depth of field of the receiving lens array is narrower than the thickness of the object to be inspected, this method shifts the depth of field position in the optical axis direction and splits the scattered light with a beam splitter, making it possible to detect the object to be inspected throughout its thickness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, in the present invention, the above-mentioned foreign matter and scratches, unevenness, defects, missing parts, attached foreign matter, etc. in an inspection target having a thickness will be simply referred to as "foreign matter / defect". An example of a foreign matter / defect inspection device according to the present invention is shown in Fig. 3A as a schematic diagram. However, it is also possible to provide an image generating device that processes a signal acquired in the foreign matter / defect inspection device into image information and outputs it.

[0029] 31 in Fig. 3A is a light source. The light source 31 is a linear arrangement of a plurality of LDs (laser diodes) or a plurality of LEDs spaced apart from each other. The light source 31 shown by the solid line in Fig. 3A is a side view, and a front view of the light source 31 is virtually shown by a two-dot chain line to the side of the light source 31 shown by 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 means 32.

[0030] The light guiding means 32 includes a collimator lens array 32a, an optical fiber array 32b, and a lens array 32c. The collimator lens array 32a includes a plurality of collimator lenses 32d arranged in a straight line. The number of the arranged collimator lenses 32d is the same as the number of the light sources 31, but the interval between adjacent collimator lenses 32d is smaller than the interval between adjacent light sources 31. The lens array 32c includes a plurality of lenses 32f arranged in a straight line. The number of the arranged lenses 32f is the same as the number of the light sources 31, and the interval between adjacent lenses 32f also matches the interval between adjacent light sources 31. The optical fiber array 32b optically connects the collimator lens array 32a and the lens array 32c. Specifically, the optical fiber array 32b includes optical fibers 32e in the same number as the number of the light sources 31, and each optical fiber 32e is associated one-to-one with each collimator lens 32d and each lens 32f.

[0031] Each lens 32f of the lens array 32c faces the position of each light source 31. The lens array 32c is for guiding the light from each light source 31 to each optical fiber 32e, and each lens 32f is arranged in almost close contact with the incident side end surface of each optical fiber 32e. The lens 32f used in the lens array 32c is preferably a microball lens or a refractive index distribution lens. Each optical fiber 32e is arranged and fixed in a line on the emission side, and the interval is narrower than that on the incidence side, and is equal to the pitch of the light receiving elements in the light receiving element array 38 (photodiode array). That is, the interval between each of the emission ends (ends on the collimator lens 32d side) of the multiple optical fibers 32e into which each of the light beams emitted from the multiple light sources 31 is incident is smaller than the interval between each of the incident ends (ends on the lens side). As a result, the interval between the optical axes of each of the light beams emitted from the multiple light sources 31 can be reduced in the arrangement direction of the multiple light sources 31, and the light beams can be guided to the inspection object 34.

[0032] The light emitted from each optical fiber 32e becomes a collimated light beam by passing through a collimator lens 32d composed of a micro lens such as a microball lens. In this way, the collimator lenses 32d collimate the light emitted from each optical fiber 32e in one-to-one correspondence with the emission end of each optical fiber 32e. The collimator lenses 32d, which are arranged in the same number as the light sources 31, have an arrangement direction that matches the arrangement direction of the light receiving elements. Since the pitch of the arrangement direction of the optical fibers 32e needs to be approximately the same as the light receiving elements (photodiodes), optical fibers 32e with a small outer diameter (cladding diameter or coating diameter) are preferable. In addition, it is also preferable that the light source 31 has low coherence. Examples of the optical fibers 32e include SI (step index) type, GI (graded index) type, and single mode type. In addition, the arrangement direction of the illumination system and the arrangement direction of the elements of the light receiving system are parallel.

[0033] The advantage of this is that there are fewer restrictions on the size of the light source 31, and the line illumination system on the emission side can be arranged more densely than on the light source 31 side. In addition, heat dissipation measures become relatively easy, which leads to increased light output from LDs and LEDs, improved operational stability, and improved durability.

[0034] The light emitted from each optical fiber 32e is collimated by a collimator lens 32d to become approximately parallel beams 33, the number of which is the same as the number of light sources 31. The collimator lens array 32a shown by a solid line in FIG. 3A is a side view, and a front view of the collimator lens array 32a is virtually shown by a two-dot chain line to the side of the collimator lens array 32a shown by a solid line. The multiple approximately parallel beams 33 are incident on an inspection object 34, and scattered light 36 scattered by a "foreign substance / defect" 35 in the inspection object 34 is captured within the depth of field of a light receiving lens array 37, and is collected at a focal position 39 of the light receiving lens array 37, and is incident on a light receiving element array 38. The light receiving element array 38 is generally a line sensor having one line in the sub-scanning direction, but may be a line sensor having multiple lines in the sub-scanning direction or an area sensor. The light receiving lens array 37 is preferably a gradient index lens array such as a SELFOC (registered trademark) lens, but may be a lens array in which a plurality of other spherical lenses are arranged in a line. The light collimated by the collimator lens 32d may be further approximately focused. Here, "approximately focused" is not limited to a configuration in which light emitted by an LED is focused, but also includes a case in which a beam waist of a laser beam is formed using a converging lens or the like. The size (beam diameter) of the light beam collimated by the collimator lens 32d or the light beam obtained by further approximately focusing the collimated light beam is preferably about 10 μm, which corresponds to "foreign matter / defect" particles in the Mie scattering region, to about 1000 μm, which corresponds to "foreign matter / defect" particles in the geometrical optical approximation region. However, the light collimated by the collimator lens 32d may be adjusted to be narrowed or expanded depending on the depth and thickness of the light scattering transmissive medium.

[0035] If the object to be inspected does not have a "foreign substance / defect," the beam remains approximately parallel and enters the light-receiving lens array 37, so it does not focus and 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, the light-receiving element array (photodiode array) 38 detects only the signal component (fluctuation component) of scattered light 36 caused by a "foreign substance / defect" with the bias component of the direct light added or subtracted.

[0036] Here, a method for suppressing crosstalk components in the light receiving element array (photodiode array) 38 will be described. When the light sources are turned on at the same time, light is illuminated in a line in the arrangement direction of the light receiving element array (photodiode array) 38. Therefore, in a situation where "foreign objects / defects" are lined up in the arrangement direction, the same light receiving element (photodiode) receives scattered light from "foreign objects / defects" at different positions at the same time, making it difficult to identify their positions. In other words, the position detection resolution decreases. A method for avoiding crosstalk is to correspond one light source to one photodiode. In other words, one way to avoid crosstalk is to correspond one light source to one light receiving element (photodiode) in one-to-one correspondence on a pixel basis. One pixel is composed of at least one light receiving element, and is not limited to a configuration in which one pixel is composed of one light receiving element, but may be a configuration in which one pixel is composed of multiple light receiving elements.

[0037] FIG. 3A will be described again. In FIG. 3A, a combination of light sources and light receiving elements is provided on one inspection surface of the inspection object. In this case, it is preferable to sequentially turn on the light sources to scan the light beam in the main scanning direction (arrangement direction of the light sources) so that adjacent light sources are not turned on at the same time. At this time, a control unit (not shown) capable of individually controlling the operation of each light source functions as an optical scanning means for scanning the light beam. The optical scanning means, light source 31, light guiding means 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 forms an image of light transmitted through the inspection surface of the inspection object on the light receiving elements of the light receiving element array (photodiode array) 38, and the lens system is included in the light receiving optical system. The set of the illumination optical system and the light receiving optical system may be movable in the optical axis direction, or the illumination optical system and the light receiving optical system may 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. In the case where there are multiple illumination optical systems, for example, multiple light sources 31 arranged in a line at a distance from each other may be configured to have multiple lines. In this case, the multiple line-shaped light sources 31 may have the same wavelength, or may have multiple line-shaped light sources 31 with different wavelengths. In the case where only the light receiving optical systems do not overlap in the optical axis direction, various means for splitting the light to the light receiving optical system are used. For example, there is a method of using one or more optical elements such as a beam splitter. Alternatively, there is a method of separating each wavelength with a dichroic mirror to identify the type of foreign matter.

[0038] Fig. 3B is a schematic diagram showing a first modified example of the "foreign matter / defect" inspection device. Fig. 3B shows a structure in which the pitch of the light receiving elements (photodiodes) is further narrowed to further improve the resolution. In this example, the light guiding means 32 includes a combination lens (reducing combination lens) 32g consisting of a combination of multiple lenses.

[0039] The combination lens 32g is disposed between the optical fiber array 32b and the inspection object 34, more specifically, between the collimator lens array 32a and the inspection object 34. The combination lens 32g is configured by a set of cylindrical lenses, for example, a combination of convex-convex lenses. This makes the interval between the optical axes of the light beams that pass through the combination lens 32g smaller than the interval between the optical axes of the light beams that enter the combination lens 32g. In this way, the pitch of the collimated light beams is appropriately reduced by the reduction ratio by a set of cylindrical lenses with different focal lengths, and can be made equal to the pitch of a higher-definition light receiving element array (photodiode array) with improved resolution.

[0040] FIG. 3C is a schematic diagram showing a second modified example of the "foreign substance / defect" inspection device. This FIG. 3C shows a structure in which the pitch of the light receiving elements (photodiodes) is further narrowed to further improve the resolution, as in the case of FIG. 3B. In this example, the combination lens (reducing combination lens) 32h included in the light guiding means 32 is composed of a set of cylindrical lenses consisting of a convex-concave combination, rather than a convex-convex combination. The convex cylindrical lens is arranged on the collimator lens array 32a side, and the concave cylindrical lens is arranged on the inspection target 34 side. Even with this configuration, the interval between the optical axes of each light beam that passes through the combination lens 32h and is emitted can be made smaller than the interval between the optical axes of each light beam that is incident on the combination lens 32h.

[0041] Although the configuration using the optical fiber array 32b has been described in Fig. 3A to Fig. 3C, the present invention is not limited to such a configuration. Currently, LEDs are becoming increasingly dense, as typified by LED printers, and 1200 dpi has already been achieved. By using this LED array, high resolution can be realized. That is, the light emitted from the LED array is collimated, and the collimated light beam is used in place of the light source of Fig. 3B or Fig. 3C. In the case of an LED printer, the lens array is a unit-magnification imaging system using a gradient index lens, but the gradient index lens used in the present invention has one focus at infinity. It is more preferable to use a high-density LD array such as a VCSEL. A specific example of the above method will be described below.

[0042] 3D is a schematic diagram showing a third modified example of the "foreign matter / defect" inspection device. In this example, a combination lens (reducing combination lens) 32i is used instead of the optical fiber array 32b, and the interval between the optical axes of the light beams emitted from the multiple light sources 31 can be reduced in the arrangement direction of the multiple light sources 31 to guide them to the inspection object 4. That is, the light guiding means 32 includes a combination lens 32i made up of a combination of multiple lenses.

[0043] 31 is an LED or LD array serving as a light source. 32a is a collimator lens array. The light source 31 and the collimator lens array 32a shown by solid lines in FIG. 3D are side views, and the front views of the light source 31 and the collimator lens array 32a are virtually shown by two-dot chain lines on the sides of the light source 31 and the collimator lens array 32a shown by solid lines. 34 is an object to be inspected, and 35 is a foreign body or defect in the object to be inspected. 37 is a light receiving lens array. 38 is a light receiving element array (photodiode array). 30 is a light beam emitted from the light source 31, and 33 is a collimated light beam emitted from the collimator lens array 32a. The collimated light beam 33 is incident on the object to be inspected 34 and then on the "foreign body / defect" 35. The light beam 33 incident on the “foreign substance / defect” 35 is scattered by the “foreign substance / defect” 35 to become scattered light 36 , which then enters a light-receiving lens array 37 and then a light-receiving element array 38 .

[0044] The combination lens 32i is disposed between the multiple light sources 31 and the inspection object 34, more specifically, between the collimator lens array 32a and the inspection object 34. The combination lens 32i is configured, for example, by a set of cylindrical lenses having a convex-convex combination, but may also be configured by a convex-concave combination. This makes the interval between the optical axes of the light beams that pass through the combination lens 32i and are emitted smaller than the interval between the optical axes of the light beams that are incident on the combination lens 32i.

[0045] Fig. 3E is a schematic diagram showing a fourth modified example of the "foreign substance / defect" inspection device. In this example, a combination lens (magnifying combination lens) 32k is added to the configuration of Fig. 3D. However, it is also possible to add the combination lens 32k to the configuration of Fig. 3B or Fig. 3C instead of the configuration of Fig. 3D.

[0046] The combination lens 32k is disposed between the inspection object 34 and the light receiving element array 38, more specifically, between the inspection object 34 and the light receiving lens array 37. The combination lens 32k is configured, for example, by a set of cylindrical lenses having a convex-convex combination, but may also be configured by a convex-concave combination. As a result, the distance between the optical axes of the light beams that pass through the combination lens 32k and are emitted becomes larger than the distance between the optical axes of the light beams that are incident on the combination lens 32k.

[0047] As in this example, if the beam is compressed using a reduction optical system and then expanded (beam spacing expanded) after the foreign object has passed, the spacing between the light receiving elements can be made wider. This allows the size of the light receiving element array to be made larger, ensuring the resolution for foreign objects while widening the light receiving area of ​​the light receiving element array, resulting in a good S / N ratio.

[0048] The lenses constituting the combination lenses 32g, 32h, 32i, and 32k shown in Figs. 3B to 3E each have power in the direction in which the light sources 31 are arranged. Here, the power of a lens is the reciprocal of the focal length, and is a measure of the refractive power of the lens. The combination lenses 32g, 32h, 32i, and 32k are each composed of a combination of lenses with different powers. In other words, the compression ratio can be changed by combining a lens with high power and a lens with low power. For example, if the power ratio is 1:3, the compression ratio is 1 / 3 and the beam interval is 1 / 3.

[0049] The number of lenses constituting the combination lenses 32g, 32h, 32i, and 32k is not limited to two, and may be three or more. The lenses constituting the combination lenses are not limited to cylindrical lenses, and may be other reduction / enlargement optical elements such as fiber optical plates. The combination lenses may also be a combination of cylindrical mirrors with different powers, a combination of cylindrical mirrors with different powers, or various combinations of spherical lenses and spherical mirrors. In addition, various lenses such as Fresnel lenses can be used.

[0050] Next, a method of splitting by a beam splitter is shown in FIG. 22. FIG. 22 shows a method in which, 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, the scattered light is split by the beam splitters 40a and 40b, and detection is possible in the entire thickness direction of the inspection object 34. In FIG. 22, three light receiving lens arrays 37a, 37b, and 37c, three light receiving element arrays 38a, 38b, and 38c, and two beam splitters 40a and 40b are provided. 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, and is collected by the light receiving lens array 37a and enters the light receiving element array 38a. A part of the light transmitted through the beam splitter 40a is reflected by the beam splitter 40b, and is collected by the light receiving lens array 37b and enters the light receiving element array 38b. The light transmitted through the beam splitter 40b is collected by the light receiving lens array 37c and enters the light receiving element array 38c. The transmittance and reflectance of each beam splitter 40a, 40b are set to be equal to each of the light receiving element arrays 38a, 38b, 38c. For example, in the case of splitting into three beams as shown in Fig. 22, the reflectance of the first incident beam splitter 40a is set to about 33%, and the reflectance of the second incident beam splitter 40b is set to 50%, so that the amount of light incident on each of the light receiving element arrays 38a, 38b, 38c is set to about 1:1:1, and the S / N ratios are also approximately equal. It is preferable that the beam splitter is not wavelength dependent and does not utilize the interference effect.

[0051] Here, the method of the present invention will be summarized once again. Figure 20 is a schematic diagram showing that a plurality of light sources of the present invention correspond one-to-one to a plurality of pixels including at least one light receiving element.

[0052] Next, a conceptual diagram of an inspection method according to the conventional technology is shown in Figure 21. However, for simplicity, the light-receiving lens system is not shown. The light source of the conventional technology in Figure 21 illuminates the entire object under inspection. Also, the light-receiving element separates the light into scattered light and non-scattered light that goes directly to the light-receiving element, and the non-scattered light contributes to foreign object detection, but it can be seen that the non-scattered light does not enter the foreign object, but mixes with the non-scattered light that goes directly to the light-receiving element from a different path of the inspection object other than the foreign object, causing crosstalk.

[0053] In contrast, in the case of Fig. 20, multiple light sources (light source array) arranged at intervals in the main scanning direction are appropriately in one-to-one correspondence. In the conceptual diagram shown in Fig. 20, since the light sources and light receiving elements are in one-to-one correspondence, it can be seen that scattered light is less likely to enter the light receiving element, and crosstalk can be suppressed.

[0054] In reality, most foreign objects and defects are not perfectly spherical, but for the sake of simplicity, they are represented as spherical particles. When the foreign object has a particle diameter of a few tens of micrometers or less, scattering in the Mie scattering region occurs. When the foreign object is as large as a raindrop of a few hundred micrometers, the geometrical optics approximation can be applied. For example, consider a case where the foreign object is a spherical particle with a diameter of 10 micrometers, the light scattering medium is resin, and the foreign object is silica. The wavelength of the light from the light source is not limited to one wavelength, and an illumination light source with multiple wavelengths may be provided. Now, if the wavelength of the light from the light source is λ=830 nm in the near infrared region, the resin is polycarbonate, the relative refractive index is Nm=1.57, and the foreign object particle is silica, the relative refractive index is Np=1.45, forward scattering occurs. For particle sizes of about several hundred μm, if there is transparency to the light source wavelength, the light will be focused and diffused in a forward scattering manner due to the lens effect, and if there is no transparency at all, a shadow will be cast that is a circle, which is the geometric optical scattering cross section. The shadow is expressed by the intensity of the light that is absorbed, diffusely reflected, transmitted and diffused. It may be necessary to consider the effect of diffraction due to the edge of the foreign particle, but it is sufficient that the sensitivity to the contrast is sharp, as long as the scattered light including diffraction is cast on the pixel or a shadow is cast. As an example, the scattered light intensity of the scattering of the spherical particle is shown in Figures 6A to 6D. Figures 6A and 6B are graphs showing forward scattering of a 10 μm particle size, and Figures 6C and 6D are graphs showing forward scattering of a 17 μm particle size, and show Mie scattering when the transparent medium is polycarbonate and the particles are silica (logarithmic scale). 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 traveling direction of the light. At the same time, it can be seen that the forward scattering ability of 17 μm particles is several times greater than that of 10 μm particles. Furthermore, graphs showing the forward scattering of foreign particles with a diameter of 25 μm are shown in Figures 6E and 6F. However, the wavelength of the incident light is λ = 1.55 μm. In this case, the forward scattering intensity is between that of 10 μm and 17 μm particles. Incidentally, the diameter of 25 μm is close to the resolution of 1200 dpi (pixel resolution: about 21 μm), and the diameter of 10 μm is close to the resolution of 2400 dpi (pixel resolution: slightly more than 10 μm). In addition, graphs showing the Mie scattering of foreign particles with a diameter of 30 μm and an incident light wavelength of 1.55 μm are shown in Figures 6G and 6H. It can be seen that the forward scattering intensity of the 30 μm particle diameter is about twice that of the 25 μm particle diameter.

[0055] A method for suppressing crosstalk components for scattered light in the Mie forward scattering region will be described below in a simplified manner. First, a description will be given with reference to FIG. 4A. FIG. 4A is a schematic diagram of receiving scattered light from a "foreign substance / defect" and shows crosstalk of the scattered light to adjacent pixels. A star-shaped mark 41 represents a foreign substance (defect). The scattered light from the foreign substance (defect) 41 is collected and imaged by a light-receiving lens array 42 onto a light-receiving element array (photodiode array) 43. FIG. 4A shows a case where multiple separate and independent light beams are simultaneously incident on a foreign substance.

[0056] The bell-shaped light intensity distribution waveform If on the left side of FIG. 4A represents the intensity distribution of 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 forms an image larger than the actual size of the "foreign substance / defect" and in a so-called blurred state due to the influence of the aberration and diffraction of the light receiving lens. In other words, even if the size of one pixel of the light receiving element (photodiode) and the size of the "foreign substance / defect" are the same in the arrangement direction of the light receiving element array (photodiode array) 43, the image size of the "foreign substance / defect" on the light receiving element (photodiode) 43 will be larger than the size of the "foreign substance / defect" due to the influence of the aberration and diffraction of the light receiving lens. It is preferable that the aperture angle of the light receiving lens is sufficiently small with respect to the angle of incidence of the scattered light, diffused light, or light having various strengths that has been absorbed, diffusely reflected, transmitted and diffused, generated by light scattering among the light that has passed through the inspection surface of the inspection object, on the light receiving lens. For example, the aperture angle is preferably about 5mrad to 15mrad, and may be 1mrad to 20mrad depending on the desired W and D. If the aperture angle is small, the amount of light received will be small, so it is necessary to relatively compensate with the power of the light source side. Furthermore, since the transmittance, which depends on the thickness of the light-scattering transmission medium, is directly related to the gain of the light-receiving sensor, a circuit configuration with an automatic gain control (AGC) in the light-receiving sensor can be used to construct a light-receiving system with a good S / N ratio and a wide dynamic range that is not dependent on various transmittances. In addition, in this case, it is also possible to use a feedback system (signal processing circuit system) that uses the average value of the output of an arbitrary pixel up to the immediately preceding output for an arbitrary pixel. At the same time, if a two-dimensional analysis of the position where the signal is captured for each line - the overall information of the output information (output data) in the depth direction of the object to be inspected is performed at the same time, real-time inspection will be possible. In any case, making efforts to match the maximum sensitivity range of the light-receiving sensor in order to improve the signal S / N ratio of the signal will further improve the signal S / N ratio, which will lead to a wider range of application in "defect and foreign body" inspection. The bell-shaped light intensity distribution waveform Ir on the right side of FIG. 4A is the intensity distribution of each of the light beams that illuminate the foreign object according to the present invention.Comparing the width of the left and right light intensity distribution waveforms in the arrangement direction on the light receiving element array (photodiode array) 43 side, it can be seen that the light intensity distribution waveform If on the light receiving element array (photodiode array) 43 side is wider than the light intensity distribution waveform Ir on the incident side.

[0057] Next, a description will be given of the two light intensity distribution waveforms If of the light receiving element array (photodiode array) 43. In the light scattering medium Ms, two "foreign bodies / defects" Mf1 and Mf2 are arranged parallel to the light receiving element array (photodiode array) 43, facing the light receiving element array (photodiode array) 43, and the interval between them is the same as the element interval of the light receiving element array (photodiode array) 43. In addition, the light receiving lens array 42 is a unity magnification system, and the WD is previously set long.

[0058] In this case, it can be seen that the light intensity distribution waveform If1 formed by the image of one of the "foreign substances / defects" Mf1 and Mf2 spreads onto the light receiving element (photodiode) PD2 adjacent to the opposite light receiving element (photodiode) PD1, causing crosstalk. The areas where crosstalk is occurring are the hatched areas Cr1 and Cr2 of each light intensity distribution waveform.

[0059] In other words, the light intensity components Cr1 and Cr2 that extend beyond the adjacent pixels are added to their own net signal components. This causes crosstalk components to be mixed into the net signal components of each light receiving element (photodiode), resulting in noise, narrowing the dynamic range and becoming one of the factors that degrade the signal SNR (Signal to Noise Ratio: synonymous with S / N).

[0060] Next, FIG. 4B will be described. FIG. 4B is a schematic diagram showing that a collimated light beam enters the light receiving lens array 42, spreads after it is emitted, and becomes background noise on the light receiving elements PD1 and PD2. The illumination used in conventional CIS and the like has a continuous light intensity distribution in the longitudinal direction of the light receiving element array (photodiode array) 43. The light scattered by the "foreign matter / defect" in the light scattering medium Ms is 44 in FIG. 4A, and in addition to this, a collimated light beam 45 is incident on the light receiving lens array 42. Since the light receiving lens array 42 is set to a unity magnification system, light from other than the vicinity of the depth of field is hardly focused. In other words, it diverges and does not contribute to imaging, so it spreads on the light receiving element array (photodiode array) 43. That is, when a collimated light beam enters the light receiving lens array 42, it spreads widely on the light receiving element array (photodiode array) 43 and becomes background noise components 46, which causes degradation of the S / N ratio. The background noise components 46 are shown in the area enclosed by a dotted square. When the background noise increases, it leads to degradation of contrast. That is, when it comes to detecting "foreign objects and defects," they become buried in the background noise components, making detection difficult.

[0061] The signal that is actually detected is a mixture of the above-mentioned crosstalk components and background noise components, and ultimately becomes a signal like that shown in Figure 5A. Figure 5B shows a case where there is almost no crosstalk or background component. In addition, in the case of geometric optical scattering, due to the shielding effect, the intensity distribution of "foreign objects / defects" becomes similar to that shown in Figure 8 described below.

[0062] In addition to the method of illuminating light receiving elements (photodiodes) and light sources in one-to-one correspondence on a pixel-by-pixel basis shown in Figs. 3A to 3E of the present invention, a method of further reducing crosstalk components will be described. In the method of simultaneously illuminating in a line as shown in Figs. 3A to 3E, components from adjacent light sources are mixed into adjacent photodiodes. A method of avoiding this is to operate only a pair of light sources and light receiving elements (photodiodes) in one-to-one correspondence, rather than lighting them simultaneously, and then move to the next pair of light sources and light receiving elements (photodiodes) in one-to-one correspondence, and repeat this sequentially until the end. In other words, the light beam from the light source at any position in the main scanning direction is detected only by the corresponding light receiving elements in one-to-one pixel units. Such control can be performed by a control unit (not shown) including a CPU individually switching ON / OFF of each light source and each light receiving element, and at this time the control unit functions as a detection means. More specifically, in synchronization with the scanning of the light beam in the illumination optical system, a signal is output only from the light receiving element near the center of the light beam at each scanning position of the multiple light receiving elements. By doing so, even if the light beam diameter is large, emitted from one light source, and collimated by a collimator lens is scattered by a "foreign substance / defect", and the scattered light is incident on a light receiving element (photodiode) that has a one-to-one correspondence in one pixel unit and then incidents on an adjacent pixel or a nearby pixel, the adjacent or nearby pixel does not output, so only a net signal for the "foreign substance / defect" corresponding to the one-to-one light source and at least one light receiving element (photodiode) in one pixel unit is obtained. At this time, the crosstalk component mentioned above is not output from other pixels, so only the collimated light beam component that is incident on the light receiving lens array is received, and crosstalk is very small.

[0063] This is shown in FIG. 7. FIG. 7 is a schematic diagram showing a multi-beam illumination-multi-scanning light receiving method. 71 is the light intensity distribution of the incident light beam, and 72 is the scattered light. 73 is the light flux when the light passing through the light receiving lens array 74 is focused on the light receiving element array (photodiode array) 75. The projected images of the scattered light of the "foreign substance / defect" Mr1 and Mr2 in the inspection object 76 are Imf1 and Imf2. As described above, the image size at this time is larger than the actual size of the "foreign substance / defect", and the image size in the arrangement direction of the light receiving element array (photodiode array) 75 becomes large and blurred due to aberration and diffraction. However, since the location where the light beam is incident is limited and the output of pixels other than the one-to-one corresponding pixel is limited, there is no output from pixels other than the pixel 77 corresponding to the incident light beam.

[0064] Also, incident light beams that have a one-to-one correspondence with another pixel 77 in a position where crosstalk is not an issue may be irradiated simultaneously. In that case, as shown in Figure 7, multiple beams can be illuminated at the same time at the same time, which has the advantage of shortening the scanning time. This method is called the "multi-beam illumination - multi-scanning light receiving method" to distinguish it from the "1-beam illumination - 1-scanning light receiving method" described above.

[0065] The spatial resolution of one pixel unit consisting of at least one light receiving element is equal to or greater 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, one pixel unit consisting of at least one light receiving element has the ability to distinguish two adjacent points within the beam diameter of the light beam. In other words, the spatial resolution of the light beam is equal to or less than the spatial resolution of a pixel unit consisting of at least one light receiving element arranged in the main scanning direction.

[0066] The scanning interval of the light beam may be equal to or less than the spatial resolution of a pixel unit consisting of at least one light receiving element arranged in the main scanning direction. In other words, the spatial resolution of a pixel unit consisting of at least one light receiving element is equal to or greater than the scanning interval of the light beam. In other words, in one pixel unit consisting of at least one light receiving element, it has the ability to distinguish two adjacent points at the scanning interval of the light beam (the interval between the light sources).

[0067] Next, we will describe the case where a "foreign substance / defect" in the object being inspected is in the geometric optical scattering region or is opaque. Scattering of the above-mentioned "foreign substance / defect" is shown in Figure 8. Cr (the hatched area) in Figure 8 is the crosstalk component of the element (center) that is operating the illumination beam for 77 adjacent pixels. The transmitted component has an intensity distribution that is lower than the peak of the adjacent bell-shaped intensity distribution. As the output of the central pixel is low and the output of the adjacent pixels is high, the presence of a "foreign substance / defect" Mr can be detected.

[0068] As described above, the signal shape changes depending on whether the "foreign object / defect" in the object being inspected is in the Mie scattering region or the geometric optical scattering region, whether it is transparent or opaque, and further on the surface property and dielectric constant, but "foreign object / defect" can be detected by the level of the detected signal, and if the signal strength and signal waveform of a foreign object are compiled in a lookup table in advance as reference data, it becomes possible to distinguish the type of "foreign object / defect" by comparing it with this reference data.

[0069] Although the object to be inspected has been described above as being a light scattering transmissive medium, the present invention can also be applied to a reflective medium. An example is shown in FIG. 9A. In FIG. 9A and FIG. 9B described later, a part of the light guiding means 32 is omitted for the sake of simplicity. FIG. 9A is a schematic diagram showing an embodiment of the reflection type, and shows a cross section in the longitudinal direction of the measurement system. 91 is an object to be inspected such as an electronic board, a paper sheet, a film, etc. Light emitted from a light source 92 such as an LED or an LD is collimated by a collimating lens 94 such as a gradient index lens or a ball lens, and is irradiated onto the object to be inspected 91. The light receiving optical system is an array of lenses, typically a gradient index lens, and is arranged so that the incident light beam and the reflected light form a diagonal 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.

[0070] In the inspection, information on the inspection object 91 as a reference is acquired in advance, and then the product is inspected. The information on the inspection object 91 as a reference is stored in memory in advance. When the inspection of the product flowing through the process is performed, it is compared with the reference information stored in advance (verification is performed). In addition, a star 98 indicates a case where a "foreign substance / defect" is attached / mixed or exists on the inspection object 91. If there is a "foreign substance / defect" on the inspection object 91, data different from the reference data is acquired, and the difference with the acquired data is obtained. It is determined that there is a "foreign substance / defect" on the inspection object 91, and the inspection object is removed from the process. In addition, a dotted line indicates a case where an element 97 is missing in 90Mf in FIG. 9A. If the dotted element is missing, data different from the reference data is acquired as described above, and it is determined from the difference that the element is missing, and it is removed from the process. Furthermore, even if fine wiring on or inside an electronic board is broken, it is similarly detected as a "foreign substance / defect".

[0071] Furthermore, even if there is a protrusion on the electronic board and the "foreign object / defect" is hidden in the shadow of the protrusion, it can be detected by irradiating the incident light beam from both sides at symmetric angles and by arranging the light receiving optical system at symmetric angles. Note that while Fig. 9A shows the case where the incident light beam is obliquely incident on the board, it may also be perpendicularly incident as in Fig. 9B and received at an angle to the board. In the case of the reflective type, the receiving angle is arranged taking into consideration the NA so that the specularly reflected light is not received. In short, the arrangement of the measurement system can be changed according to the object to be inspected.

[0072] The method of the present invention is also effective when the object to be inspected is a printed matter or a functional film. That is, in the case of a transmissive film, it is effective for inspecting for scratches, etc., and in the case of opaque printed matter such as paper sheets, a reflective type is used, and it is effective for inspecting not only scratches but also printing defects, etc. Furthermore, in the present invention, since the depth of field is deep, it can be used even in places where the conveying system moves up and down, expanding the range of application.

[0073] In addition, in the case of a light scattering transmissive medium, particularly in a medium with low transmittance, it may be better to narrow the light beam. In this case, the narrowing angle of the light beam is determined taking into consideration the receiving solid angle of the light receiving element. Furthermore, when the transmittance of the light scattering transmissive medium is high or the reflectance of the reflective medium is high, expanding the light beam to a certain extent has the effect of reducing the light received in the receiving solid angle of the light receiving element from becoming background noise. Therefore, the signal-to-noise ratio of the signal can be further improved by devising a method of collimating the light beam or narrowing or widening the light beam according to the transmittance or reflectance of the object to be inspected. Note that "narrowing or widening the light beam" means further narrowing or widening the collimated parallel light beam. Although a detailed description of the above is omitted, to put it simply, in the case of a light scattering transmissive medium, assuming that the receiving solid angle hardly changes in the depth direction, it is possible to suppress the collimated parallel light beam from being directly incident on the light receiving element, and in the case of a reflective medium, the incident intensity of the direct illumination beam in the receiving solid angle can be reduced if the light beam is spread on the inspection surface of the inspection object, and the S / N ratio of the signal based on the light received by the light receiving element is improved. Note that the inspection surface of the inspection object is the surface on the inspection object on which the light beam is incident, and is not limited to one, and may be configured such that the light beam is incident on multiple inspection surfaces.

[0074] Currently, LEDs are becoming increasingly dense, as typified by LED printers, and 1200 dpi has already been achieved. High resolution can be achieved by using this LED array. That is, the light emitted from the LED array is collimated, and the collimated light beam is used instead of the light source of FIG. 3A. In the case of an LED printer, the refractive index distribution lens array is an equal-magnification imaging system of a refractive index distribution lens, but the refractive index distribution lens used in the present invention has a focus at infinity. If LDs can be arranged at high density in the future, it is more preferable to use a high-output LD array. Alternatively, a line-shaped light source in which semiconductor lasers, typified by VCSELs (Vertical Surface Emitting Lasers), are arranged on a plane, or an area-shaped light source may be used. Line-shaped light sources can be arranged in multiple lines, and inspection accuracy can be improved by inspection using multiple wavelengths.

[0075] The above method will be explained again with reference to Figs. 3A to 3E. 31 is an LED or LD array that is a light source. 32a is a collimator lens array. 34 is an object to be inspected, and 35 is a "foreign substance / defect" in the object to be inspected. 37 is a light receiving lens array. 38 is a light receiving element array (photodiode array). 30 is a light beam emitted from the light source 31, and 33 is a light beam emitted from the collimator lens 32. The light beam 33 is incident on the object to be inspected 34, and then on the "foreign substance / defect" 35. The light beam 33 that is incident on the "foreign substance / defect" 35 is scattered by the "foreign substance / defect" 35, becoming scattered light 36, which is incident on the light receiving lens array 37, and then on the light receiving element array 38.

[0076] Next, using FIG. 4B, which is a schematic diagram showing how a collimated light beam enters the light-receiving lens array 42, expands after exiting, and becomes background noise on the light-receiving elements PD1 and PD2, we will describe an even better method for removing the background noise shown in FIG. 4B.

[0077] In the light receiving optical system of FIG. 4B, background noise cannot be completely removed, but can only be suppressed to a certain extent. In order to further remove the background noise and obtain only the required net signal components, a separate device is required. The device is described below. The biggest drawback of the multi-lens is that the crosstalk components from the adjacent multi-lenses spread considerably due to the multi-lens structure, and the background noise components spread on the element surface of the light receiving element array (photodiode array) 43. The crosstalk components become smaller because the light beam spreads, resulting in attenuation. However, there is still room for improvement, and the S / N ratio can be further improved by further reducing the background noise. Figure 10 shows a schematic diagram of this method. Figure 10 shows a method in which an aperture (array) corresponding to each of the multi-lenses in the light receiving system is provided.

[0078] In FIG. 10, 101 indicates apertures corresponding to each of the multi-lenses of the light receiving system as viewed from the optical axis direction. 102 indicates an imaginary cross section of the aperture. At the same time, each aperture 101 is located on the optical axis of each light source, collimator lens (including a convergent lens that forms a beam waist in some cases), light receiving lens, and light receiving element, and is approximately equal to or smaller than the NA of the light receiving lens. Alternatively, an aperture may be placed on the image plane of the light receiving lens, and the spread light may be received in one-to-one correspondence. In this case, the one-to-one correspondence may be corrected in advance, and only signals from one pixel unit with one-to-one correspondence may be output.

[0079] FIG. 11 is a schematic diagram showing the case where adjacent collimated light beams overlap. As shown in FIG. 11, the collimated light beam may be larger than the effective diameter of the multi-lens of the light receiving system. By making it larger, it becomes possible to detect all foreign objects and defects in the object to be inspected. 103 is the part where the collimated light beams overlap, and 104 is the part where they do not overlap. A "foreign object / defect" 105 is irradiated with the light beam where adjacent collimated light beams overlap, and a "foreign object / defect" 106 is irradiated with the light beam where they do not overlap. As a result, "foreign objects / defects" in all positions can be detected.

[0080] An example of an embodiment of the present invention will be described in detail with reference to the above-mentioned FIGS. 3A to 3E. The light source 31 is preferably a VCSEL (Vertical Cavity Surface Emitting Laser) which is easy to form into an array or matrix and has high power. Alternatively, an LED array such as that used in an LED printer may be used. The VCSELs are closely arranged in a line, and the pitch of the light source 31 is determined. For example, it is set to 600 dpi or 1200 dpi. However, this is not limited to the case where it is used in cases other than image processing. Next, the VCSEL array is arranged in parallel to the gradient index lens array. The gradient index lens array is used as a collimator, so a pitch close to 1 / 4 pitch is used. Alternatively, it may be close to 3 / 4 pitch. In other words, the pitch may be determined so that the light can be emitted as a collimated light beam. In addition to the gradient index lens, a microlens array in which spherical lenses are made minute may be used. In this case, the microlenses are arranged in accordance with the optical axis of the light source 31. In the case of a collimated light beam, the beam waist is assumed to be on the emission surface of the VCSEL, and the beam is collimated so that the beam waist coincides with the focal point of the collimator lens 32d.

[0081] In the present invention, a laser with a wavelength suitable for light scattering and transmitting media is used, and in particular for food-related products, a wavelength of about λ=800nm ​​to 900nm is used, taking into consideration absorption by moisture. Some foods (confectionery such as cacao) have low transmittance in the above wavelength band, and in this case, a wavelength of about λ=1500nm, which is used for optical communication, may be used. 2 O, CO 2 , O 2 Materials that contain a large amount of substances such as food also have wavelength ranges with high transmittance, so the wavelength can be selected as necessary to illuminate the object to be inspected. When a wavelength is selected, a light receiving element with a sensitivity range for the selected wavelength is used. For rolled paper, rolled film, paper sheets, resin films, metal films, and other objects other than food, wavelengths in the visible range may be used.

[0082] In this embodiment, a wavelength in the near infrared region, λ=830 nm, was used. At this wavelength, it is preferable to suppress the change in beam diameter to about 5% at a distance of ±5 mm when the thickness of the light scattering transmissive medium is 10 mm and the beam waist is placed at the center of the light scattering transmissive medium. For example, if the size of the VCSEL's output port is 10 μm in diameter, the beam diameter d after collimation is d=210 μm according to formula 1, where f is the focal length of the SELFOC (registered trademark) lens array and f=2 mm. W0={4·f·λ / (π·d)} / 2 ···(Equation 1) Where: f: focal length of lens λ: wavelength of the laser beam d: Beam diameter It is.

[0083] Alternatively, a method of focusing the light at the center of the light scattering transmissive medium may be used. In other words, the beam waist length may be adjusted so that the beam becomes approximately parallel in the light scattering transmissive medium. In this case, Kogelnik's formula 2 is used to find the beam diameter at the beam waist position. However, since the refractive index of a light scattering transmissive medium is different from that in air (vacuum), the beam waist position must be determined taking into consideration the movement of the beam waist position; details will be given later. Kogelnik's formula 2, which describes the propagation of a laser beam, is used to determine the range of the allowable beam radius. W 2 (z)=W0 2 [1+{λ z / (π W0 2 )} 2 ] ...(Formula 2) Where: W(z): Beam radius at any position along the optical axis W0: Beam waist radius It is. Since the beam waist radius W0 is calculated by Equation 1, the range of the beam diameter with an error of, for example, 5% can be determined by Equation 2. The result of Equation 2 is 217 μm, which is within the allowable range.

[0084] The position of the beam waist in air (vacuum) is determined by formula 1, but in a light scattering transparent medium, the refractive index is greater than in air (vacuum), so the actual position of the beam waist is farther from the light source. And the beam waist diameter also changes as the convergence angle becomes shallower. The movement distance Δf of the beam waist can be expressed by formula 3. In other words, it can be determined by the focal length of the focusing lens when the laser beam is incident on the entrance end face and the beam diameter of the collimated beam. Since this is a distance that does not require consideration of beams near the diffraction limit, θ' is approximately calculated using geometric optics and Snell's Law. Δf=tanθ´ / di (Equation 3) Where: θ: Maximum angle of incidence θ´: Maximum refraction angle di: Beam radius at the incident end surface entering a light scattering transparent medium It is.

[0085] Since Kogelnik's formula is no longer applicable in light scattering and transmitting media, the beam waist diameter must be calculated anew. Since it is not necessary to use the convergence angle near the beam waist, the refraction angle calculated by Snell's Law, a geometric optics approximation, is used. The beam divergence angle Φ can be expressed by Equation 4, which represents the diffraction limit. Φ=2λ / (π dms) (Eq. 4) Where: λ´: wavelength in a light scattering transparent medium dms: beam waist diameter in a light scattering transparent medium λ´: N λ (λ: refractive index in air (vacuum)) It is.

[0086] From the above, the beam waist diameter dms in the light scattering transmissive medium is as long as the focal length is almost equal to the WD, and when a condenser lens with a small NA (Numerical Aperture) f=50 mm is used, and the condenser lens is placed behind 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 210 μm, the beam waist diameter 2W0 in the absence of the light scattering transmissive medium is 252 μm. It can be seen that the focal movement distance in the light scattering transmissive medium when a lens with the above focal length is used is 21 mm. Therefore, when the beam waist position is placed in the center, the illumination optical system should be lowered by 16 mm from the light scattering transmissive medium. In addition, the beam diameter dms is 377 μm from Equation 4. From the above, the position of the optical system should be determined according to the thickness and refractive index of the object to be inspected. Also, the optical system may be structured so that it can be moved in the optical axis direction in this way.

[0087] FIG. 12A shows a schematic diagram of an experiment using the edge method according to an embodiment of the present invention, and FIGS. 14A to 14D show actual measurement results. FIG. 12B shows a schematic diagram of an experiment using the edge method according to the conventional technology, and FIGS. 15A to 15D show actual measurement results using the conventional technology. In FIG. 12A and FIG. 12B, a part of the light guide means 32 is omitted for the sake of simplicity. In FIG. 12A and FIG. 12B, 34a is a diffuser plate. FIG. 14A shows the case of two diffusers, FIG. 14B shows the case of three diffusers, FIG. 14C shows the case of four diffusers, and FIG. 14D shows the case of five diffusers (standard values). FIG. 15A shows the case of two diffusers, FIG. 15B shows the case of three diffusers, FIG. 15C shows the case of four diffusers, and FIG. 15D shows the case of five diffusers (standard values). In this measurement, instead of "foreign matter / defect", the edge was used as the measurement target to verify the performance of the present invention, and the rising characteristics of the edge signal were observed. The light scattering transmission medium was a diffuser plate Kuraray Comoglass 432L (thickness: t = 2 mm, total light transmittance: 61%, haze: 95%), and the number of plates was set to 2, 3, 4, and 5, with a maximum thickness of 10 mm, in order to confirm and verify the difference in thickness. Figures 14A(1), 14B(1), 14C(1), and 14D(1) show the results for each number of diffusers, and Figures 15A(1), 15B(1), 15C(1), and 15D(1) show the rising characteristics of the edge signal of the conventional method as a comparison example. The light source used was a collimated light beam from LD (Panasonic LNCT28PS01WW). Figure 13 shows the beam profile of the semiconductor laser in the inspection target. To treat it as an array, one LD was moved at each pixel pitch, and signals were obtained for each corresponding pixel.

[0088] FIG. 14A(1), FIG. 14B(1), FIG. 14C(1), and FIG. 14D(1) are graphs showing the edge response (relative intensity) in one example of the embodiment of the present invention. The pixel size is about 62 μm in the main scanning direction. Also, FIG. 14A(2), FIG. 14B(2), FIG. 14C(2), and FIG. 14D(2) show the difference (relative intensity) between the outputs from adjacent pixels. As is clear from FIG. 14A(2), FIG. 14B(2), FIG. 14C(2), and FIG. 14D(2), the difference between adjacent pixels is clearly present, and the difference in relative intensity is 10% of the peak value, so it is possible to discriminate on a pixel-by-pixel basis (equivalent to 400 dpi). If the element size is further reduced and the pixel size and pitch are made smaller and narrower, it is possible to achieve a resolution of 600 dpi, 1200 dpi, or even higher. It is preferable that the size of the light receiving element (pixel size) is set to satisfy 200 dpi or more.

[0089] Figures 15A to 15D show edge responses (relative intensity) according to conventional technology as a comparative example. There is a clear difference between the present invention and the conventional technology, with the conventional technology lacking pixel resolution for any diffuser plate, and the graph showing the difference being buried in background noise (random noise), making foreign object detection impossible. In contrast, the present invention shows that foreign object detection is possible for any diffuser plate thickness.

[0090] Next, the results of the response of the light receiving sensor when a "foreign substance / defect" exists in a light scattering transmissive medium with a thickness (t=30 mm) in the optical axis direction are shown by a simulation model. A schematic diagram of the model is shown in FIG. 16. In FIG. 16, a part of the light guiding means 32 is omitted for the sake of simplicity. PMMA was selected as the object to be inspected, and silicone spherical particles with a diameter of 2 μm were used as the light scattering particles. The concentration was changed from 0.04 wt% to 0.20 wt%. The light source was collimated and had a cross-sectional size of 150 μm, which is larger than the light receiving element (main scanning direction size: 62 μm). FIGS. 17A to 17F are graphs showing the results of the simulation, and FIGS. 17A to 17F are graphs showing the results of the simulation. The foreign substance was a sphere with a diameter of 100 μm, and was an absorber with an interface with a transmittance of 0%. The foreign substance particle was located at the center of the object to be inspected. The foreign substance particle was located at the center of the object to be inspected. FIG. 17A shows the case where the scattering particle concentration is 0.00 wt%, FIG. 17B shows the case where the scattering particle concentration is 0.04 wt%, FIG. 17C shows the case where the scattering particle concentration is 0.08 wt%, FIG. 17D shows the case where the scattering particle concentration is 0.12 wt%, and FIG. 17E shows the case where the scattering particle concentration is 0.16 wt%, and FIG. 17F shows a comparison of the output at each concentration.

[0091] 18A to 18F and 19A to 19F show graphs of simulation results of a foreign particle located ±14.5 mm away from the center of the object to be inspected. That is, the foreign particle is located at a depth of 0.5 mm from the end of the object to be inspected. FIGS. 18A to 18F show a case where the foreign particle is located at the end of the object to be inspected on the light source side, and FIGS. 19A to 19F show a case where the foreign particle is located at the end of the object to be inspected on the light receiving element side. According to these simulation results, both responses are very similar to the case of a foreign particle located at the center of a light scattering transmissive medium, which clearly shows the effect of the present invention and shows that the present invention is very suitable for detecting "foreign objects / defects" in a thick light scattering transmissive medium.

[0092] As described above, it is understood that the present invention is superior to the conventional technology in the detection accuracy of "foreign bodies and defects" in light-diffusing transparent media. In addition, the method of the present invention can also be applied to the detection of "foreign bodies and defects" in reflective media. Furthermore, it is possible to generate an image based on the light receiving signal from the light-scattering transparent medium, and to further analyze the defective products that have been removed based on the level of the detection signal. In this case, it is assumed that offline inspection will be mainly performed, not online, but by improving the signal processing speed, it is also possible to automatically perform online analysis. In this way, inspections that were not possible with the conventional technology become possible, the quality of the inspection will be further improved, and ultimately the quality of the products to be inspected can be improved. <Action and effect>

[0093] As described above, by using a collimated parallel light beam with a sufficiently small diameter, or by adjusting the beam waist so that the beam becomes a nearly parallel light beam in a light scattering and transparent inspection object, and further by adjusting the light beam focusing angle and spreading angle according to the inspection object, it is possible to suppress overlapping of light spreading due to light scattering (diffusion), and by selecting the output signal from the pixel so that only the signal near the optical axis of the light beam is received by the light receiving element of one pixel unit having one-to-one correspondence with the light source at each irradiation position, it is possible to suppress crosstalk between pixels, and it is possible to separate and detect light that causes background noise due to scattered light (diffused light) and direct incident light, etc., and light amount changes due to "foreign matter / defects", so that "foreign matter / defects" in the inspection object can be clearly identified and accurate inspection can be performed. In addition, the light guiding means enables high-resolution detection. Furthermore, if a light-receiving system that expands the beam spacing that was once narrowed is installed, the spacing between the light-receiving elements can be unified while maintaining the resolution for "foreign objects and defects" in the object being inspected, which results in cost reduction effects and an improvement in the S / N ratio by allowing the size of the light-receiving elements to be increased. [Explanation of symbols]

[0094] 10 Linear lighting source 11 Lens Array 12 Light receiving part 31 Light source 32 Light guiding means 32a Collimator lens array 32b Optical fiber array 32c Lens Array 32d collimator lens 32e Optical Fiber 32f Lens 32g, 32h, 32i, 32k combination lenses 33 Light Beam 34 Inspection object 36 Scattered light 37 Receiving lens array 38 Photodetector array 39 Focus position 42 Receiving lens array 45 Light Beam 74 Receiving lens array 76 Inspection Objects 77 pixels 91 Inspection object 92 Light source 94 Collimating Lens 95 Receiving lens array

Claims

1. an illumination optical system including an optical scanning means for scanning, over at least one inspection surface of an inspection object having light scattering properties, a light beam obtained by collimating light emitted from a plurality of light sources arranged at a distance from one another in a line, or a light beam obtained by further approximately converging the collimated light beam; a light receiving optical system including a plurality of light receiving elements that are arranged parallel to a scanning direction of the illumination optical system so that one pixel unit consisting of the light source and at least one light receiving element has a one-to-one correspondence, the light beam that has passed through an inspection surface of the inspection object is irradiated onto a foreign substance or defect on the inspection object, and that receives scattered light, diffused light, or light having varying intensity that has been absorbed, diffusely reflected, or transmitted and diffused from the foreign substance or defect; a detection means for detecting a light beam from the light source at any position in a main scanning direction of the illumination optical system by only a corresponding light receiving element, a spatial resolution of one pixel unit consisting of the at least one light receiving element is equal to or greater than a spatial resolution of the light beam formed by an illumination optical system on an inspection surface of an object to be inspected before the light beam is transmitted through or reflected by the inspection surface, a light guiding unit that reduces the spacing between the optical axes of each light beam emitted from the plurality of light sources in the arrangement direction of the plurality of light sources and guides the light beams to an object to be inspected.

2. an illumination optical system including an optical scanning means for scanning a light beam adjusted to converge or to diverge, the light beam being emitted from a plurality of light sources arranged at a distance from one another in a line, on at least one inspection surface of an inspection object having light scattering properties; a light receiving optical system including a plurality of light receiving elements that are arranged parallel to a scanning direction of the illumination optical system so that one pixel unit consisting of the light source and at least one light receiving element has a one-to-one correspondence, the light beam that has passed through an inspection surface of the inspection object is irradiated onto a foreign substance or defect on the inspection object, and that receives scattered light, diffused light, or light having varying intensity that has been absorbed, diffusely reflected, or transmitted and diffused from the foreign substance or defect; a detection means for detecting a light beam from the light source at any position in a main scanning direction of the illumination optical system by only a corresponding light receiving element, a spatial resolution of one pixel unit consisting of the at least one light receiving element is equal to or greater than a spatial resolution of the light beam formed by an illumination optical system on an inspection surface of an object to be inspected before the light beam is transmitted through or reflected by the inspection surface, a light guiding unit that reduces the spacing between the optical axes of each light beam emitted from the plurality of light sources in the arrangement direction of the plurality of light sources and guides the light beams to an object to be inspected.

3. the light guiding means 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, 3. The foreign matter / defect inspection device according to claim 1, wherein the distance between the output ends of the optical fibers is smaller than the distance between the input ends of the optical fibers.

4. the light guiding means includes a plurality of collimator lenses that correspond one-to-one to the output ends of the optical fibers and collimate the output light from each optical fiber; 4. The foreign matter / defect inspection device according to claim 3, wherein the plurality of collimator lenses are arranged in the same number as the plurality of light sources, and the arrangement direction of the collimator lenses coincides with the arrangement direction of the light receiving elements.

5. the light guiding means includes a reduction combination lens consisting of a combination of a plurality of lenses arranged between the optical fiber array and the inspection object, or a reduction combination lens consisting of a combination of a plurality of lenses arranged between the plurality of light sources and the inspection object, a distance between the optical axes of the light beams emitted through the reduction combination lens is smaller than a distance between the optical axes of the light beams incident on the reduction combination lens, the light receiving optical system includes a magnifying combination lens formed by a combination of a plurality of lenses arranged between the inspection object and the plurality of light receiving elements, 5. A foreign body / defect inspection device according to claim 3, wherein the distance between the optical axes of each light beam emitted after passing through the magnifying combination lens is larger than the distance between the optical axes of each light beam incident on the magnifying combination lens.

6. The plurality of light sources arranged in a line at a distance from each other have a plurality of lines, and are a plurality of line-shaped light sources of the same wavelength, or are a plurality of line-shaped light sources of different wavelengths; 3. The foreign particle / defect inspection apparatus according to claim 1, wherein the interval between said light sources of said illumination optical system is equal to or less than a spatial resolution in pixel units formed of at least one light receiving element arranged in a main scanning direction.

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

8. 8. The foreign matter / defect inspection device according to claim 1, wherein the light receiving optical system has a lens system that forms an image of light transmitted through an inspection surface of the inspection object on the light receiving element.

9. 9. The foreign body / defect inspection device according to claim 1, wherein the detection means outputs signals only for light receiving elements in the vicinity of a center of the light beam at each scanning position of the plurality of light receiving elements in synchronization with scanning of the light beam in the illumination optical system.

10. 10. The foreign matter / defect inspection device according to claim 1, further comprising a plurality of combinations of the light source and the at least one light receiving element in one pixel unit on one inspection surface of the object to be inspected.

11. 2. The foreign body / defect inspection device according to claim 1, wherein a light source of the illumination optical system is a light source consisting of at least one LD or at least one LED, and a light beam obtained by collimating the light beam emitted from the light source or a light beam obtained by further approximately concentrating the collimated light beam can scan the inspection surface of the inspection object in the arrangement direction of the multiple light receiving elements.

12. 2. The foreign particle / defect inspection apparatus according to claim 1, wherein the set of the illumination optical system and the light receiving optical system is movable in the direction of an optical axis.

13. 13. The foreign matter / defect inspection device according to claim 1, wherein the light receiving element is a line sensor or an area sensor.

14. the light receiving optical system includes a lens array; The lens array includes a multi-lens having a one-to-one correspondence with each pixel, 14. The foreign matter and defect inspection device according to claim 1, wherein an aperture having a one-to-one correspondence with each pixel is provided between the multi-lens and each pixel, and each aperture is positioned on the optical axis of each light source.

15. 15. The foreign matter / defect inspection device according to claim 1, characterized in that the object to be inspected has at least one inspection surface, and has at least one depth of field region in the optical axis direction.

16. a step of scanning a light beam by an illumination optical system including an optical scanning means for scanning a light beam obtained by collimating light emitted from a plurality of light sources arranged at a distance from each other in a line, or a light beam obtained by further approximately converging the collimated light beam, against at least one or more inspection surfaces of an inspection object having light scattering properties; a step of arranging the light source and one pixel unit consisting of at least one light receiving element in a one-to-one correspondence in parallel to a scanning direction of the illumination optical system, the light beam transmitted through an inspection surface of the inspection object being irradiated onto a foreign substance or defect on the inspection object, and receiving the light beam by a light receiving optical system including a plurality of light receiving elements that receive scattered light, diffused light, or light having varying strengths that has been absorbed, diffusely reflected, or transmitted and diffused from the foreign substance or defect; a step of detecting a light beam from the light source at any position in a main scanning direction of the illumination optical system only by a corresponding light receiving element, a spatial resolution of one pixel unit consisting of the at least one light receiving element is equal to or greater than a spatial resolution of the light beam formed by an illumination optical system on an inspection surface of an object to be inspected before the light beam is transmitted through or reflected by the inspection surface, a light guiding means for guiding each light beam emitted from the plurality of light sources to an object to be inspected by reducing the distance 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.

17. a step of scanning a light beam by an illumination optical system including a light scanning means for scanning a light beam adjusted to converge or to diverge, the light beam being emitted from a plurality of light sources arranged at a distance from one another in a line, against at least one inspection surface of an inspection object having light scattering properties; a step of arranging the light source and one pixel unit consisting of at least one light receiving element in a one-to-one correspondence in parallel to a scanning direction of the illumination optical system, the light beam transmitted through an inspection surface of the inspection object being irradiated onto a foreign substance or defect on the inspection object, and receiving the light beam by a light receiving optical system including a plurality of light receiving elements that receive scattered light, diffused light, or light having varying strengths that has been absorbed, diffusely reflected, or transmitted and diffused from the foreign substance or defect; a step of detecting a light beam from the light source at any position in a main scanning direction of the illumination optical system only by a corresponding light receiving element, a spatial resolution of one pixel unit consisting of the at least one light receiving element is equal to or greater than a spatial resolution of the light beam formed by an illumination optical system on an inspection surface of an object to be inspected before the light beam is transmitted through or reflected by the inspection surface, a light guiding means for guiding each light beam emitted from the plurality of light sources to an object to be inspected by reducing the distance 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.

18. the light guiding means 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, The distance between the output ends of the optical fibers is smaller than the distance between the input ends of the optical fibers; the light guiding means includes a plurality of collimator lenses that correspond one-to-one to the output ends of the optical fibers and collimate the output light from each optical fiber; 18. The foreign matter / defect inspection method according to claim 16, wherein the plurality of collimator lenses are arranged in the same number as the plurality of light sources, and the arrangement direction of the collimator lenses coincides with the arrangement direction of the light receiving elements.

19. the light guiding means includes a reduction combination lens consisting of a combination of a plurality of lenses arranged between the optical fiber array and the inspection object, or a reduction combination lens consisting of a combination of a plurality of lenses arranged between the plurality of light sources and the inspection object, 20. The foreign body / defect inspection method according to claim 18, wherein the spacing between the optical axes of each light beam that passes through the reduction combination lens and is emitted is smaller than the spacing between the optical axes of each light beam that is incident on the reduction combination lens.

20. the illumination optical system includes a magnifying combination lens that is a combination of a plurality of lenses and that is disposed between an inspection object and the plurality of light receiving elements; 20. The foreign body / defect inspection method according to claim 19, wherein the interval between the optical axes of each light beam that passes through the magnifying combination lens and is emitted is greater than the interval between the optical axes of each light beam that is incident on the magnifying combination lens.

21. 18. The foreign matter / defect inspection method according to claim 16, wherein the interval between said light sources of said illumination optical system is equal to or less than a spatial resolution in pixel units formed of at least one light receiving element arranged in the main scanning direction.

Images