JP7777962B2 - Inspection lighting device and inspection system - Google Patents

Description

The present invention relates to an inspection lighting device for inspecting, for example, the side surfaces of a workpiece.

In visual inspections of workpieces such as tablets that are roughly flattened and cylindrical, not only the flat and bottom surfaces of the workpiece are inspected based on captured images, but also the entire circumference of the side surfaces. In the inspection system described in Patent Document 1, the tablet is held in a holding groove formed in a drum with approximately half of its side surface exposed, and transported to the camera's imaging area. Once imaging of one side surface is complete, the other side surface is held in another drum with the same structure, with the other side surface exposed, and imaging is performed in the same way. In other words, by changing the orientation in which the tablet is held and imaging twice, an image of the entire circumference of the tablet is obtained.

However, such an inspection system requires a very complex mechanism and at least two cameras as the imaging mechanism. Despite this, it is not possible to simultaneously image the entire circumference of the side surface. For this reason, it is difficult to reduce the time required to image the entire circumference of the workpiece's side surface.

Japanese Patent Application Laid-Open No. 2001-74664

The present invention was made in consideration of the problems described above, and aims to provide an inspection illumination device that has a simple configuration, can capture the entire periphery of the side of a workpiece in a single image, and achieves a good S/N ratio.

In other words, the inspection illumination device according to the present invention comprises a first optical system including a first illumination optical path through which first inspection light reaches a first side surface of a workpiece and a first detection optical path from the first side surface to an imaging mechanism, and configured so that the first inspection light is irradiated onto the first side surface while being polarized in a predetermined direction; and a second optical system including a second illumination optical path through which second inspection light reaches a second side surface of the workpiece opposite the first side surface, and a second detection optical path from the second side surface to the imaging mechanism, and configured so that the second inspection light is irradiated onto the second side surface while being polarized in the same direction as the first inspection light. The inspection illumination device according to the present invention is characterized in that it is configured so that at least some of the polarized components of the first inspection light and second inspection light that have been reflected or scattered by the workpiece and have undergone a change in polarization are incident on the imaging mechanism, and so that light polarized in the predetermined direction is prevented from entering the imaging mechanism.

With this configuration, the first inspection light reflected or scattered by the first side surface and the second inspection light reflected or scattered by the second side surface can be simultaneously incident on the imaging mechanism, making it possible to image the entire circumference of the side surface of the workpiece at once. Furthermore, the passing light of the first inspection light that is not irradiated on the workpiece but is incident on the second optical system on the opposite side of the workpiece and travels along the second detection optical path toward the imaging mechanism can be prevented from entering the imaging mechanism. Similarly, the light of the second inspection light that is not irradiated on the workpiece but is incident on the first optical system on the opposite side of the workpiece can also be prevented from entering the imaging mechanism. Therefore, only the light that is the signal component reflected or scattered on the first and second side surfaces of the workpiece can be incident on the imaging mechanism, while the light that is the noise component not irradiated on the workpiece can be prevented from entering the imaging mechanism, thereby improving the S/N ratio of the captured image.

In one specific configuration of the inspection illumination device according to the present invention, the first optical system includes a first light source that emits first inspection light, a first polarization control element that polarizes the first inspection light emitted from the first light source in the predetermined direction, and a first beam splitter that is provided between the first polarization control element and the workpiece and transmits the first inspection light that has passed through the first polarization control element to the workpiece and reflects the first inspection light that has been reflected or scattered by the workpiece; and the second optical system includes a second light source that emits second inspection light, and a first polarization control element that polarizes the first inspection light emitted from the second light source in the predetermined direction. a second polarization control element that polarizes the second inspection light that has passed through the second polarization control element in the predetermined direction; and a second beam splitter that is provided between the second polarization control element and the work and transmits the second inspection light that has passed through the second polarization control element toward the work and reflects the second inspection light that has been reflected or scattered by the work; and further includes a polarization selection mechanism that is provided on the first detection optical path and the second detection optical path and is configured to block light polarized in the predetermined direction and transmit at least a portion of light polarized in directions other than the predetermined direction.

To minimize the number of optical elements constituting the polarization selection mechanism and achieve its function with a simple configuration, the polarization selection mechanism may consist of a single polarizer located in front of the imaging mechanism on the first detection optical path and the second detection optical path.

In order to compactly configure the first and second optical systems and reduce the number of boundary surfaces and optical elements through which the first and second inspection lights pass before reaching the imaging mechanism, thereby suppressing attenuation of the radiant flux and increasing the radiant flux incident on the imaging mechanism, the first optical system comprises a first light source that emits the first inspection light, and a first beam splitter that is provided between the first light source and the workpiece and transmits the first inspection light emitted from the first light source to the workpiece and reflects the first inspection light reflected or scattered by the workpiece, and The transmission-reflection surface of the splitter is configured to polarize the first inspection light emitted from the first light source in the predetermined direction, the second optical system includes a second light source that emits second inspection light, and a second beam splitter that is provided between the second light source and the work and transmits the second inspection light emitted from the second light source toward the work and reflects the second inspection light reflected or scattered by the work, and the transmission-reflection surface of the second beam splitter is configured to polarize the second inspection light emitted from the second light source in the predetermined direction.

When the first beam splitter and the second beam splitter have a polarization function, a specific configuration example for enabling the polarization selection mechanism to achieve that function without using a polarizer and further reduce the number of parts is one in which the polarization state of light is maintained on the first detection optical path between the first side surface and the transmission-reflection surface of the first beam splitter, and the polarization state of light is maintained on the second detection optical path between the second side surface and the transmission-reflection surface of the second beam splitter. In this configuration, light that has been reflected or scattered by the workpiece and undergoes a change in polarization is reflected by each beam splitter and directed to the imaging mechanism, while light that has not been irradiated onto the workpiece remains polarized in a predetermined direction and can pass through the other beam splitter again and escape to the other light source. Therefore, the first beam splitter and the second beam splitter can function not only as a polarization control mechanism but also as the polarization selection mechanism described above.

To ensure that the first inspection light and the second inspection light contain almost no polarization components other than those in the specified direction, thereby improving the accuracy of the linear polarization and enabling imaging of even minute defects on each side surface, the first optical system may further include a first illumination-side polarizing element between the first light source and the transmission-reflection surface of the first beam splitter that polarizes the first inspection light in the specified direction, and the second optical system may further include a second illumination-side polarizing element between the second light source and the transmission-reflection surface of the second beam splitter that polarizes the second inspection light in the specified direction.

To prevent the aforementioned S/N ratio from decreasing due to the influence of the incidence angle dependency of each optical element polarizing the first and second inspection lights in a predetermined direction and the extinction ratio of the polarizer, the first optical system may further include a first detection-side polarizing element between the transmission-reflection surface of the first beam splitter and the imaging mechanism that transmits light polarized in a direction perpendicular to the predetermined direction, and the second optical system may further include a second detection-side polarizing element between the transmission-reflection surface of the second beam splitter and the imaging mechanism that transmits light polarized in a direction perpendicular to the predetermined direction. Here, "light polarized in a direction perpendicular to the predetermined direction" does not only mean light whose polarization direction is strictly 90 degrees relative to the predetermined direction, but also includes, for example, light whose polarization direction forms an angle close to 90 degrees with respect to the predetermined direction. In other words, any polarization direction may be used so that the polarization selection mechanism blocks light polarized in the predetermined direction while allowing light reflected or scattered at the side of the workpiece to pass through the polarization selection mechanism.

To prevent errors in the imaging results of the first and second side portions of the workpiece due to the spectral reflectance of the workpiece or chromatic aberration in the imaging mechanism, the second inspection light must have the same wavelength as the first inspection light. In this case, the irradiation conditions of the first and second inspection lights irradiated onto the workpiece, including not only polarization but also wavelength, are aligned, so that, for example, only defects or scratches on each side portion of the workpiece will appear as differences in the imaging results.

Another aspect of the present invention includes a first optical system including a first illumination optical path through which first inspection light having a first wavelength reaches a first side portion of the workpiece and a first detection optical path from the first side portion to the imaging mechanism; a second optical system including a second illumination optical path through which second inspection light having a second wavelength different from the first wavelength reaches a second side portion of the workpiece opposite the first side portion and a second detection optical path from the second side portion to the imaging mechanism; a first wavelength-selective filter provided on the first detection optical path that transmits light of the first wavelength and blocks light of the second wavelength; and a second wavelength-selective filter provided on the second detection optical path that transmits light of the second wavelength and blocks light of the first wavelength. This configuration makes it possible to simultaneously image the first and second side portions of the workpiece without using polarized light. Furthermore, each wavelength selection filter allows signal component light reflected or scattered by the workpiece to enter the imaging mechanism, while preventing noise component light that passes through without being irradiated onto the workpiece from entering the imaging mechanism, thereby improving the S/N ratio in the captured image.

An inspection system equipped with the inspection illumination device of the present invention and the imaging mechanism can, for example, image the entire circumference of the side of the workpiece at once. Therefore, there is no need to use a complex transport mechanism to capture multiple images in order to image the entire circumference of the side of the workpiece, as was done in the past.

In order to capture images of a wider range of the workpiece, even if the workpiece is cylindrical and has curved side surfaces, the imaging mechanism may include an imaging element and an object-side telecentric lens that forms an image of the first and second side surfaces of the workpiece on the imaging element.

In this way, with the inspection illumination device of the present invention, it is possible to obtain an image of the entire circumference of, for example, the side of the workpiece in a single image capture, significantly reducing the time required for inspection. Furthermore, since only the light that becomes the signal component reflected or scattered by the side of the workpiece is allowed to enter the imaging mechanism, and light that causes noise is blocked, the S/N ratio of the captured image can be increased.

1 is a schematic diagram showing an inspection illumination device and an inspection system according to a first embodiment of the present invention; FIG. 10 is a comparison diagram showing the state of inspection light on the side surface of a workpiece when an object-side telecentric lens is used in the first embodiment, and the state of inspection light on the side surface of a workpiece when another general lens, such as a macro lens, is used. FIG. 10 is a schematic diagram showing an inspection illumination device and an inspection system according to a second embodiment of the present invention. FIG. 10 is a schematic diagram showing an inspection illumination device and an inspection system according to a third embodiment of the present invention. 10A and 10B are schematic diagrams illustrating the polarization action of a polarizing beam splitter according to the third embodiment. FIG. 10 is a schematic diagram showing a modified example of the inspection illumination device and inspection system according to the third embodiment of the present invention. FIG. 10 is a schematic diagram showing yet another modified example of the inspection illumination device and inspection system according to the third embodiment of the present invention. FIG. 10 is a schematic diagram showing an inspection illumination device and an inspection system according to a fourth embodiment of the present invention.

The inspection illumination device 100 according to the first embodiment of the present invention and the inspection system 200 equipped with this inspection illumination device 100 and an imaging mechanism 4 will be described with reference to Figure 1.

This inspection system 200 is used to visually inspect the shape and presence or absence of defects of a workpiece W, which has a roughly flattened cylindrical shape, such as a tablet, based on captured images of the side surfaces W1 and W2. In the first embodiment, the optical axis OA of the lens 41 of the camera, which is the imaging mechanism 4, is set so as to be perpendicular to the center of the flat surface W3 (front surface) or bottom surface W4 (back surface) where the end faces of the workpiece W are formed. In other words, the central axis of the workpiece W and the optical axis OA of the lens 41 are aligned. Inspection light is irradiated from two directions, sandwiching the side surfaces W1 and W2 of the workpiece W with the optical axis OA of the lens 41 set in this way, by a pair of optical systems. More specifically, the optical axes of the inspection light beams, which travel in opposite directions near the workpiece W, are configured to be perpendicular to the optical axis OA of the lens 41. The inspection light reflected or scattered by the side surfaces W1, W2 of the workpiece W is redirected by various optical elements and ultimately guided to the imaging mechanism 4, which is configured to capture an image of the entire circumference of the side surfaces W1, W2 of the workpiece W at once. Furthermore, the inspection light that is not irradiated onto the workpiece W is configured not to enter the imaging mechanism 4. The shape of the workpiece W is not limited to a cylindrical shape, and various shapes can be used.

More specifically, the inspection system 200 includes the imaging mechanism 4 and an inspection lighting device 100 configured to irradiate the side portions W1 and W2 of the workpiece W with inspection light polarized in a predetermined direction and to guide only the inspection light reflected or scattered by the workpiece W to the imaging mechanism 4.

First, the details of the inspection illumination device 100 will be described with reference to Figure 1. In the following description, the left half of the circumference of the side portions W1 and W2 of the workpiece W will be defined as the first side portion W1, and the right half of the circumference of the side portions W1 and W2 of the workpiece W will be defined as the second side portion W2.

The inspection illumination device 100 comprises a first optical system 1 that irradiates a first side surface W1 with first inspection light polarized in a predetermined direction; a second optical system 2 that irradiates a second side surface W2 of the workpiece W that is opposite the first side surface W1 with second inspection light polarized in the same direction as the first inspection light; and a polarization selection mechanism 3 that is configured to allow at least some of the polarization components of the first inspection light and second inspection light that have been reflected or scattered by the workpiece W and have undergone a change in polarization to enter the imaging mechanism 4, while preventing light polarized in the predetermined direction from entering the imaging mechanism 4. Note that in the first embodiment, the first optical system 1 and the second optical system 2 are arranged symmetrically with respect to a reference plane RP that includes the central axis of the workpiece W.

The first optical system 1 is shown in the left half of Figure 1. The first optical system 1 includes a first illumination optical path L11 extending from the first light source 11 to the first side surface W1 of the workpiece W, and a first detection optical path L12 extending from the first side surface W1 to the imaging mechanism 4. The first illumination optical path L11 is an optical path that extends linearly in the left-right direction in Figure 1. The first detection optical path L12 is an optical path that extends in a zigzag pattern and is reflected multiple times. The first illumination optical path L11 and the first detection optical path L12 overlap between the workpiece W and the first beam splitter 13, which will be described later.

Specifically, the first optical system 1 includes a first light source 11, a first polarization control element 12, a first beam splitter 13, a first mirror 14, and a first reflecting surface 15 of the common mirror CM. The first light source 11, the first polarization control element 12, and the first beam splitter 13 are arranged in a straight line in the left-right direction in FIG. 1, forming the first illumination light path L11. The first beam splitter 13, the first mirror 14, and the first reflecting surface 15 of the common mirror CM are arranged in a crank shape, forming the first detection light path L12.

The first light source 11 emits randomly polarized light (natural light) at a predetermined wavelength as the first inspection light, and is composed of, for example, an LED.

The first polarization control element 12 is a polarizer that transmits only light polarized in a predetermined direction from the first inspection light emitted from the first light source 11, converting the first inspection light into a linearly polarized state. Note that the first polarization control element 12 is not limited to a polarizer and may be a polarization conversion element, etc. Use of a polarization conversion element makes it possible to extract the first inspection light emitted from the first light source 11 as polarized light in a predetermined direction more efficiently than when a polarizer is used. In the first embodiment, the first inspection light changes from a randomly polarized state to a P-polarized state by passing through the first polarization control element 12.

The first beam splitter 13 is, for example, cube-shaped, and the orientation of its transmission-reflection surface 13S is set so that the first inspection light in a P-polarized state that has passed through the first polarization control element 12 is transmitted to the first side surface of the workpiece W, and the first inspection light that has been reflected or scattered by the first side surface W1 of the workpiece W is reflected to the first mirror 14. Note that the first beam splitter 13 is not limited to being cube-shaped, and may also be plate-shaped.

The first mirror 14 has a reflecting surface oriented so that it bends the direction of travel of light reflected by the first beam splitter 13 at a right angle and reflects it toward the common mirror CM. The light reflected by the first mirror 14 is then bent by a further 90 degrees by the first reflecting surface 15 of the common mirror CM and reflected toward the imaging mechanism 4.

Here, the width of the first inspection light traveling through the first illumination optical path L11 is set larger than the vertical and horizontal widths of the workpiece W. Therefore, light of the first inspection light near the optical axis is illuminated onto the first side surface W1 of the workpiece W, but light outside of that is not illuminated onto the workpiece W and instead enters the second beam splitter 23 of the second optical system 2, which will be described later. If the workpiece W is a tablet, its surface is a scattering surface, so the polarization state of the illuminated first inspection light is not preserved. Therefore, the first inspection light reflected or scattered by the first side surface W1 of the workpiece W changes from P polarization to random polarization. On the other hand, the first inspection light that is not illuminated onto the workpiece W and enters the second optical system 2 remains P polarization as it travels through the second detection optical path L22 of the second optical system 2 and reaches the polarization selection mechanism 3.

The second optical system 2 is the optical system shown in the right half of Figure 1. The second optical system 2 includes a second illumination optical path L21 extending from the second light source 21 to the second side surface W2 of the workpiece W, and a second detection optical path L22 extending from the second side surface W2 to the imaging mechanism 4. The second illumination optical path L21 is an optical path that extends linearly in the left-right direction in Figure 1. The second detection optical path L22 is an optical path that extends in a zigzag pattern and is reflected multiple times. The second illumination optical path L21 and the second detection optical path L22 overlap between the workpiece W and the second beam splitter 23, which will be described later.

Specifically, the second optical system 2 includes a second light source 21, a second polarization control element 22, a second beam splitter 23, a second mirror 24, and a second reflecting surface 25 of the common mirror CM. The arrangement of these optical elements is symmetrical to the arrangement of the optical elements of the first optical system 1 described above, so further explanation will be omitted.

The second light source 21 is of the same type and model as the first light source 11 and is composed of, for example, an LED. That is, the second light source 21 emits randomly polarized light at the same predetermined wavelength as the first light source 11 as the second inspection light.

The second polarization control element 22 is a polarizer that transmits only light polarized in a predetermined direction from the second inspection light emitted from the second light source 21, converting the second inspection light into a linearly polarized state. Note that the second polarization control element 22 is not limited to a polarizer and may be a polarization conversion element, etc. In the first embodiment, the second inspection light changes from a randomly polarized state to a P-polarized state by passing through the second polarization control element 22. In other words, after passing through each polarization control element, the first inspection light and second inspection light are irradiated onto the workpiece W with the same wavelength and the same polarization state.

The second beam splitter 23 is, for example, cube-shaped, and the orientation of its transmission/reflection surface 23S is set so that the second inspection light in a P-polarized state that has passed through the second polarization control element 22 is transmitted toward the second side surface of the workpiece W, and the second inspection light that has been reflected or scattered by the second side surface portion W2 of the workpiece W is reflected toward the second mirror 24. Note that the second beam splitter 23 is not limited to being cube-shaped, and may also be plate-shaped.

The second mirror 24 has a reflecting surface oriented so that it bends the direction of travel of the light reflected by the second beam splitter 23 at a right angle and reflects it toward the common mirror CM. The light reflected by the second mirror 24 is then bent by a further 90 degrees by the second reflecting surface 25 of the common mirror CM and reflected toward the imaging mechanism 4.

Here, the width of the second inspection light traveling through the second illumination optical path L21 is set larger than the vertical and horizontal widths of the workpiece W. Therefore, light of the second inspection light near the optical axis is illuminated onto the second side surface W2 of the workpiece W, but light outside of that is not illuminated onto the workpiece W and instead enters the first beam splitter 13 of the first optical system 1 described above. Like the first inspection light, the second inspection light reflected or scattered by the second side surface W2 of the workpiece W also changes from P polarization to random polarization. On the other hand, the second inspection light that is not illuminated onto the workpiece W and enters the first optical system 1 remains P polarization as it travels through the first detection optical path L12 of the first optical system 1 and reaches the polarization selection mechanism 3.

The polarization selection mechanism 3 is provided on the first detection light path L12 and the second detection light path L22 between the common mirror CM and the imaging mechanism 4. This polarization selection mechanism 3 is configured to transmit at least a portion of the light reflected or scattered by the first side surface W1 or the second side surface W2 of the workpiece W, while preventing the components of the first inspection light and the second inspection light that are not irradiated onto the workpiece W from entering the imaging mechanism 4. More specifically, the polarization selection mechanism 3 is a polarizer configured to transmit S-polarized light and block P-polarized light. Therefore, the first inspection light and second inspection light reflected or scattered by the workpiece W that reach the polarization selection mechanism 3 are in a random polarization state, and only the S-polarized light enters the imaging mechanism 4. On the other hand, the first inspection light and second inspection light that are not irradiated onto the workpiece W travel only by reflection on the second detection light path L22 and the first detection light path L12, and therefore maintain their P-polarized state until they reach the polarization selection mechanism 3. As a result, the first and second inspection lights that are not irradiated onto the workpiece W are blocked by the polarization selection mechanism 3 and do not enter the imaging mechanism 4.

Finally, the imaging mechanism 4 will be described in detail. The imaging mechanism 4 includes an imaging element 43, a lens 41 that forms an object-side telecentric lens and an aperture 42 that images the first side surface W1 and the second side surface W2 of the workpiece W on the imaging element 43. As shown in FIG. 1, only the first inspection light reflected or scattered by the first side surface W1 of the workpiece W and the second inspection light reflected or scattered by the second side surface W2 of the workpiece W are simultaneously incident on the imaging mechanism 4. Therefore, the entire circumference of the side surfaces W1 and W2 of the workpiece W can be imaged simultaneously on the imaging element 43. Furthermore, because an object-side telecentric lens is used, the chief rays are not inclined at any point on the side surfaces W1 and W2 of the workpiece W, which are circularly curved surfaces, as shown in FIG. 2, and the chief rays are parallel to each other. On the other hand, when a typical lens, such as a macro lens, is used, the chief rays of the lens are inclined toward the outer edge. Therefore, when the workpiece W has a cylindrical shape, using an object-side telecentric lens allows a wider area of the workpiece W to be imaged than when using a macro lens.

With the inspection illumination device 100 and inspection system 200 of the first embodiment configured as described above, the first inspection light and the second inspection light can be simultaneously irradiated along the entire circumference of the side portions W1 and W2, and only the first inspection light and the second inspection light reflected or scattered by the first side portion W1 and the second side portion W2 of the workpiece W can be incident on the imaging mechanism 4 at one time. As a result, a captured image showing the entire circumference of the side portions W1 and W2 of the workpiece W can be obtained with just one imaging session. Therefore, compared to the conventional method of capturing images of the side portions W1 and W2 of the workpiece W in two separate sessions, each capturing half the circumference, the time required to capture the entire circumference of the side portions W1 and W2 can be reduced by approximately half.

Furthermore, the first inspection light and second inspection light, which become noise components that are not irradiated onto the workpiece W, do not enter the imaging mechanism 4, improving the S/N ratio of the signal light originating from the side portions W1 and W2 of the workpiece W. In this way, only the light originating from the side portions W1 and W2 of the workpiece W is reflected in the captured image, making it possible to detect, for example, minute shape differences around the entire periphery of the side portions W1 and W2 of the workpiece W, as well as minute defects, with high accuracy.

Furthermore, because the first optical system 1 and the second optical system 2 are bilaterally symmetrical and have the same configuration, light of the same wavelength and polarization state can be irradiated onto the first side surface W1 and the second side surface W2. This makes it possible to achieve substantially the same illumination conditions around the entire circumference of the side surfaces W1 and W2 of the workpiece W, preventing detection errors due to, for example, chromatic aberration in the imaging mechanism 4.

Next, an inspection illumination device 100 and an inspection system 200 according to a second embodiment of the present invention will be described with reference to Figure 3. Note that in each embodiment described below, components corresponding to those described in the first embodiment will be designated by the same reference numerals.

The inspection illumination device 100 of the second embodiment differs from the first embodiment in the arrangement and alignment of the optical elements in each optical system. In the first embodiment, the first light source 11 and the second light source 21 were configured to illuminate the first side surface W1 and the second side surface W2 directly from the side of the workpiece W so that the first illumination light path L11 and the second illumination light path L21 were linear. In contrast, in the second embodiment, the first light source 11 and the second light source 21 are provided on the imaging mechanism 4 side when viewed from the workpiece W, and the light emission direction is set to be parallel to the optical axis OA of the lens 41. In other words, the first illumination light path L11 and the second illumination light path L21 are configured to be approximately L-shaped, and the first detection light path L12 and the second detection light path L22 are configured to be zigzag-shaped, as in the first embodiment.

More specifically, each optical system is configured so that the inspection light travels in the following order: light source 11, 21, polarization control element 12, 22, beam splitter 13, 23, mirror 14, 24, side surface W1, W2 of workpiece W, mirror 14, 24, beam splitter 13, 23, reflective surface 15, 25 of common mirror CM, polarization selection mechanism 3, and imaging mechanism 4. In other words, rather than directly irradiating the side surface W1, W2 of workpiece W with the inspection light transmitted through beam splitters 13, 23 as in the first embodiment, the inspection light is first reflected by a mirror before being irradiated onto the side surface W1, W2 of workpiece W.

With the inspection illumination device 100 and inspection system 200 of the second embodiment, the light sources and imaging mechanism 4 can be arranged together, resulting in a more compact device configuration than the first embodiment. Furthermore, as with the first embodiment, the entire circumference of the side portions W1 and W2 of the workpiece W can be imaged at once, and the inspection light that is not irradiated onto the workpiece W is prevented from entering the imaging mechanism 4, thereby increasing the S/N ratio.

Next, the third embodiment of the inspection illumination device 100 and inspection system 200 will be described with reference to Figures 4 and 5.

The inspection illumination device 100 and inspection system 200 of the third embodiment differ from the first embodiment in that they do not include polarization control elements 12 and 22, do not include a polarizer immediately before the imaging mechanism 4, and the beam splitters 13 and 23 are polarizing beam splitters. As shown in FIG. 5 , in the third embodiment, the first beam splitter 13 and the second beam splitter 23 are polarizing beam splitters configured to transmit the P-polarized component and reflect the S-polarized component of light incident on the transmission-reflection surfaces 13S and 23S. The polarization state of light is maintained between the first side surface W1 and the transmission-reflection surface 13S of the first beam splitter 13 on the first detection optical path L11, and between the second side surface W2 and the transmission-reflection surface 23S of the second beam splitter 23 on the second detection optical path L22. Specifically, no optical elements such as polarizers are provided between the transmission/reflection surfaces 13S, 23S of each beam splitter and the side surfaces W1, W2 of the workpiece W, and the polarization state of the light is maintained. Below, it will be explained that in the third embodiment, light that is irradiated onto the workpiece W and reflected or scattered enters the imaging mechanism 4, while light that is not irradiated onto the workpiece W does not enter the imaging mechanism 4.

The first inspection light emitted from the first light source 11 has a random polarization state. At the transmission/reflection surface 13S of the first beam splitter 13, the P-polarized component is transmitted toward the workpiece W, and the S-polarized component is reflected toward the opposite side of the imaging mechanism 4.

Of the first inspection light that passes through the first beam splitter 13 and becomes P-polarized, the light that is irradiated onto the first side surface W1 of the workpiece W changes to a random polarization state due to reflection or scattering on the diffuse reflection surface of the workpiece W. The first inspection light that returns from the workpiece W to the first beam splitter 13 is transmitted by the transmission-reflection surface 13S to the first light source 11 side, while only the S-polarized component is reflected, and is then guided to the imaging mechanism 4 by the first mirror 14 and the first reflection surface 15.

On the other hand, of the first inspection light that passes through the first beam splitter 13 and becomes P-polarized, the light that is not irradiated onto the first side surface W1 of the workpiece W remains P-polarized and enters the transmission-reflection surface 23S of the second beam splitter 23. Here, the second beam splitter 23 has the same optical properties as the first beam splitter 13, and transmits the P-polarized component. Therefore, the first inspection light that is not irradiated onto the workpiece W can pass through the second beam splitter 23 and escape to the second light source 21, and does not enter the imaging mechanism 4 from the second optical system 2.

In the second optical system 2, as in the first optical system 1 described above, only the component of the second inspection light that is irradiated onto the workpiece W is incident on the imaging mechanism 4.

In this way, with the inspection illumination device 100 and inspection system 200 of the third embodiment, the polarization control elements 12, 22 and the polarizer that functions as the polarization selection mechanism 3 in the first embodiment are omitted, and only the inspection light irradiated onto the side portions W1, W2 of the workpiece W is incident on the imaging mechanism 4, making it possible to image the entire circumference of the side portions W1, W2 at once. Furthermore, by having the beam splitters 13, 23 perform the functions of two polarizers, the number of times the radiant flux is halved can be reduced by two, making it possible to increase the radiant flux incident on the imaging mechanism 4 by four times compared to the first embodiment.

A modified example of the third embodiment will be described with reference to Figure 6. In this modified example, the polarization control elements 12, 22 and the polarizer provided as the polarization selection mechanism 3 in the inspection illumination device 100 and inspection system 200 of the second embodiment shown in Figure 3 are omitted, and the first beam splitter 13 and second beam splitter 23 are replaced with polarizing beam splitters that transmit P-polarized light components and reflect S-polarized light components. As is clear from the optical path diagram in Figure 6, in this modified example, the first beam splitter 13 and second beam splitter 23 still function as the polarization selection mechanism 3, allowing only the inspection light irradiated onto the side portions W1 and W2 of the workpiece W to enter the imaging mechanism 4.

Another variant of the third embodiment will be described with reference to Figure 7. In the variant shown in Figure 6, polarization control elements 12, 22 and polarization selection mechanism 3 are omitted by using polarizing beam splitters 13, 23. However, to enable more precise control of the polarization state, elements for controlling polarization other than polarizing beam splitters 13, 23 may be provided. Specifically, as shown in Figure 7, a first illumination-side polarizing element 17 that transmits P-polarized light may be provided between the first light source 11 and the first beam splitter 13, which transmits P-polarized light and reflects S-polarized light at its transmission-reflection surface 13S, and a first detection-side polarizing element 18 that transmits S-polarized light may be provided between the transmission-reflection surface 13S of the first beam splitter 13 and the imaging mechanism 4. Similarly, a second illumination-side polarizing element 27 that transmits P-polarized light may be provided between the second light source 21 and the second beam splitter 23, which transmits P-polarized light and reflects S-polarized light at its transmission-reflection surface 23S, and a second detection-side polarizing element 28 that transmits S-polarized light may be provided between the transmission-reflection surface 23S of the second beam splitter 23 and the imaging mechanism 4. In this modified example, the first detection-side polarizing element 18 and the second detection-side polarizing element 28 may be integrated into a single polarizer, similar to the polarization selection mechanism 3, and provided between the common mirror CM and the imaging mechanism 4.

Next, the inspection illumination device 100 and inspection system 200 of the fourth embodiment will be described with reference to Figure 8. In the fourth embodiment, the wavelengths of the first inspection light and the second inspection light are made different, so that only the light irradiated onto the side portions W1 and W2 of the workpiece W enters the imaging mechanism 4.

That is, the first optical system 1 includes a first illumination optical path L11 through which first inspection light having a first wavelength reaches the first side surface W1 of the workpiece W, and a first detection optical path L12 from the first side surface W1 to the imaging mechanism 4. Furthermore, a first wavelength-selective filter 16 is provided on the first detection optical path L12, which transmits light of the first wavelength and blocks light of the second wavelength.

The second optical system 2 includes a second illumination optical path L21 through which second inspection light having a second wavelength different from the first wavelength reaches a second side surface W2 of the workpiece W, which is on the opposite side of the first side surface W1, and a second detection optical path L22 from the second side surface W2 to the imaging mechanism 4. Furthermore, a second wavelength selection filter 26 is further provided on the second detection optical path L22, which transmits light of the second wavelength and blocks light of the first wavelength.

In this embodiment, the first wavelength corresponds to blue, and the second wavelength corresponds to red.

Specifically, the first optical system 1 includes a first light source 11 that emits light of a first wavelength corresponding to blue, a first beam splitter 13, and a first mirror 14 and a first reflecting surface 15 that, together with the first beam splitter 13, form the first detection light path L12. In the fourth embodiment, a first wavelength-selective filter 16 that transmits blue light and blocks red light is provided between the first beam splitter 13 and the first mirror 14. Note that in the fourth embodiment, as in the first embodiment, the first light source 11 of the first optical system 1 is configured to emit light horizontally. However, as in the second embodiment, the first light source 11 may be configured to emit light in the same direction as the optical axis OA of the imaging mechanism 4, and the light reflected by the beam splitter or mirror may be incident on the workpiece W.

The second optical system 2 is configured to be plane-symmetrical to the first optical system 1 with respect to a reference plane RP including the central axis of the workpiece W. That is, the second optical system 2 includes a second light source 21 that emits light of a second wavelength corresponding to red, a second beam splitter 23, and a second mirror 24 and a second reflecting surface 25 that, together with the second beam splitter 23, form a second detection light path L22. In the fourth embodiment, a second wavelength-selective filter 26 that transmits red light and blocks blue light is provided between the second beam splitter 23 and the second mirror 24. Note that in the fourth embodiment, as in the first embodiment, the second light source 21 of the second optical system 2 is configured to emit light horizontally. However, as in the second embodiment, the second light source 21 may be configured to emit light in the same direction as the optical axis OA of the imaging mechanism 4, and the light reflected by the beam splitter or mirror may be incident on the workpiece W.

In the inspection illumination device 100 and inspection system 200 of the fourth embodiment configured in this manner, the first optical system 1 allows only the blue light reflected or scattered by the first side surface of the workpiece W to pass through the first detection optical path L12 and enter the imaging mechanism 4, while the red light emitted from the second light source 21 that is not irradiated onto the workpiece W is blocked by the first wavelength selection filter 16 and does not enter the imaging mechanism 4. Similarly, the second optical system 2 allows only the red light reflected or scattered by the second side surface of the workpiece W to pass through the second detection optical path L22 and enter the imaging mechanism 4, while the blue light emitted from the first light source 11 that is not irradiated onto the workpiece W is blocked by the second wavelength selection filter 26 and does not enter the imaging mechanism 4.

As a result, the entire circumference of the side portions W1 and W2 of the workpiece W can be imaged at once, and light that does not originate from the side portions W1 and W2 of the workpiece W can be blocked, improving the S/N ratio of the signal related to the side portions W1 and W2.

Other embodiments will be described below.

The polarizer provided as the polarization selection mechanism in the first and second embodiments is not limited to being provided between the common mirror and the imaging mechanism. The polarization selection mechanism may be provided anywhere between the transmission/reflection surface of the beam splitter and the imaging mechanism, and instead of a single polarizer, the polarization selection mechanism may be configured by providing individual polarizers for each of the first and second optical systems.

The relationship between P-polarized light and S-polarized light described in the first and second embodiments can be reversed and still hold true, so the characteristics of the polarization control element and polarizer can be selected accordingly. Furthermore, the polarization selection mechanism only needs to block the polarized light of the first and second inspection light when they enter the side of the workpiece, and transmit other polarized light components.

The workpieces targeted by this invention are not limited to tablets, but may be of various shapes and materials. For example, if the workpiece is not cylindrical, the flat or bottom surface is defined as the portion that intersects with the optical axis of the lens, and the surface perpendicular to the flat or bottom surface is defined as the side surface, and the orientation of each optical system can be set accordingly. Furthermore, the optical axis of the lens does not have to be perpendicular to the flat or bottom surface of the workpiece, but may intersect at an angle at a predetermined angle. In addition, the irradiation light path does not have to be perpendicular to the optical axis of the lens, but may intersect at an angle.

The imaging mechanism is not limited to one that captures images from the flat surface side of the workpiece, but may also capture images from the bottom surface side. Furthermore, the imaging mechanism may be configured to capture not only the side surface of the workpiece, but also the entire periphery of the side surface, as well as the flat surface or bottom surface simultaneously. In the first embodiment, for example, the individual reflecting mirrors and common mirror may be omitted, and the imaging mechanism may be configured so that light from the side surface and light from the flat surface simultaneously enter the imaging mechanism.

In the first to third embodiments, the first light source and the second light source are configured as separate light sources, but they may be combined into a single shared light source, for example. The shared light source may be split into two optical paths using a mirror or the like, and each may be incident on a polarization control element or a polarizing beam splitter, so that each has the same polarization state. Furthermore, the first light source and the second light source may have different wavelengths.

In the fourth embodiment, the wavelength of the inspection light emitted from each light source may be selected as appropriate. In other words, it is not limited to blue or red, and the wavelength selection filter may be selected so that only the desired light is incident on the imaging mechanism. Furthermore, in the fourth embodiment, the wavelength selection filter may be located anywhere between the transmission/reflection surface of the beam splitter and the imaging mechanism.

The first side surface and the second side surface are not limited to being defined by dividing the entire circumference of the workpiece side surface in half. For example, the first side surface irradiated with the first inspection light and the second side surface irradiated with the second inspection light may partially overlap, or there may be an area between the first side surface and the second side surface that is not irradiated with the inspection light.

In addition, various modifications of the embodiments and combinations of parts of each embodiment may be made as long as they do not contradict the spirit of the present invention.

1: First optical system 2: Second optical system 3: Polarization selection mechanism 4: Imaging mechanism 11: First light source 12: First polarization control element 13: First beam splitter 16: First wavelength selection filter 17: First illumination side polarization element 18: First detection side polarization element 21: Second light source 22: Second polarization control element 23: Second beam splitter 26: Second wavelength selection filter 27: Second illumination side polarization element 28: Second detection side polarization element 100: Inspection illumination device 200: Inspection system W: Work W1: First side surface portion W2: Second side surface portion

Claims (10)

An inspection lighting device that is applied to a workpiece and reflects or scatters irradiated light by changing the polarization state,
a first optical system including a first irradiation optical path through which a first inspection light reaches a first side surface of the workpiece, and a first detection optical path from the first side surface to an imaging mechanism, and configured so that the first inspection light is irradiated onto the first side surface while being polarized in a predetermined direction;
a second optical system including a second irradiation optical path through which the second inspection light reaches a second side surface of the workpiece opposite the first side surface, and a second detection optical path from the second side surface to the imaging mechanism, and configured so that the second inspection light is irradiated onto the second side surface while being polarized in the same direction as the first inspection light;
An inspection lighting device configured to cause at least some of the polarization components of the first inspection light and the second inspection light, which have been reflected or scattered by the work and have undergone a change in polarization, to be incident on the same imaging mechanism, while preventing light polarized in the specified direction from being incident on the imaging mechanism. The first optical system is
a first light source that emits a first inspection light;
a first polarization control element that polarizes the first inspection light emitted from the first light source in the predetermined direction;
a first beam splitter that is provided between the first polarization control element and the work, and transmits the first inspection light that has passed through the first polarization control element to the work side, and reflects the first inspection light that has been reflected or scattered by the work,
The second optical system is
a second light source that emits second inspection light;
a second polarization control element that polarizes the second inspection light emitted from the second light source in the predetermined direction;
a second beam splitter provided between the second polarization control element and the work, for transmitting the second inspection light that has passed through the second polarization control element to the work side, and for reflecting the second inspection light that has been reflected or scattered by the work,
2. The inspection illumination device according to claim 1, further comprising a polarization selection mechanism provided on the first detection optical path and the second detection optical path, configured to block light polarized in the predetermined direction and transmit at least a portion of light polarized in directions other than the predetermined direction. The inspection illumination device described in claim 2, wherein the polarization selection mechanism is a single polarizer provided in front of the imaging mechanism on the first detection optical path and the second detection optical path. The first optical system is
a first light source that emits a first inspection light;
a first beam splitter that is provided between the first light source and the work, transmits the first inspection light emitted from the first light source to the work side, and reflects the first inspection light reflected or scattered by the work;
The second optical system is
a second light source that emits second inspection light;
a second beam splitter that is provided between the second light source and the work, and transmits the second inspection light emitted from the second light source to the work side, and reflects the second inspection light reflected or scattered by the work,
2. The inspection illumination device according to claim 1, wherein the first beam splitter and the second beam splitter are polarizing beam splitters configured to transmit components of the incident light polarized in the predetermined direction and reflect components polarized in a direction perpendicular to the predetermined direction. The first optical system is
a first illumination-side polarizing element disposed between the first light source and the transmission-reflection surface of the first beam splitter to polarize the first inspection light in the predetermined direction;
The second optical system is
5. The inspection illumination device according to claim 4, further comprising a second illumination-side polarizing element disposed between the second light source and the transmission-reflection surface of the second beam splitter for polarizing the second inspection light in the predetermined direction. The first optical system is
a first detection-side polarizing element that transmits light polarized in a direction orthogonal to the predetermined direction, between the transmission-reflection surface of the first beam splitter and the imaging mechanism;
The second optical system is
6. An inspection illumination device according to claim 4, further comprising a second detection-side polarizing element between the transmission-reflection surface of the second beam splitter and the imaging mechanism, the second detection-side polarizing element transmitting light polarized in a direction perpendicular to the predetermined direction. An inspection lighting device according to any one of claims 1 to 6, wherein the second inspection light has the same wavelength as the first inspection light. a first optical system including a first irradiation optical path through which first inspection light having a first wavelength reaches a first side surface portion of the workpiece, and a first detection optical path from the first side surface portion to an imaging mechanism;
a second optical system including a second irradiation optical path through which second inspection light having a second wavelength different from the first wavelength reaches a second side surface of the workpiece opposite the first side surface, and a second detection optical path from the second side surface to the imaging mechanism;
a first wavelength selection filter provided on the first detection optical path, the first wavelength selection filter transmitting light of the first wavelength and blocking light of the second wavelength;
a second wavelength selection filter provided on the second detection optical path, the second wavelength selection filter transmitting light of the second wavelength and blocking light of the first wavelength,
An inspection illumination device configured to direct at least a portion of the first inspection light and the second inspection light reflected or scattered by the workpiece into the same imaging mechanism. The inspection illumination device according to any one of claims 1 to 8,
An inspection system comprising the imaging mechanism. The imaging mechanism
An imaging element;
The inspection system according to claim 9 , further comprising an object-side telecentric lens that forms an image of the first side surface portion and the second side surface portion of the workpiece on the imaging element.