JP2005241692A - Optical device, imaging apparatus and inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device by which a reflected image and a transmitted image are observed using a simple constitution, and to provide an imaging apparatus and an inspection device. <P>SOLUTION: The imaging apparatus for imaging an FPD 1, using light transmitted through the FPD 1, is equipped with a vertical illumination light source 11; an objective 14 guiding the light from the light source 11 to the front of the FPD 1; a filter 20 arranged between the light source 11 and the FPD 1 and having a light-shielding part for shielding the center part from light and a light-transmitting part provided around the light-shielding part; a retroreflection sheet 23 arranged on the back side of the FPD 1 and retroreflecting the light in the same direction as an incident direction; and a camera 15 receiving transmitted light retroreflected by the sheet 23 and transmitted through the FPD 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical apparatus, an imaging apparatus, and an inspection apparatus that perform observation, imaging, and the like of a transmitted image with light transmitted through a target object.

  In a conventional inspection apparatus for a liquid crystal display device, both an incident light source and a transmitted light source are used to separately capture an image by reflected light and an image by transmitted light. This inspection apparatus will be described with reference to FIG. FIG. 7 is a plan view showing a configuration of a conventional liquid crystal display device inspection apparatus. Reference numeral 101 denotes an FPD, 111 denotes an epi-illumination light source, 112 denotes an epi-illumination condenser lens, 113 denotes a half mirror, 114 denotes an imaging lens, 115 denotes a CCD camera, 121 denotes a transmission light source, and 122 denotes a transmission light condenser lens.

  In this inspection apparatus, an optical system for illuminating the FPD 101 of the object to be inspected with two illuminations of an incident light source 111 and a transmission light source 121 is provided. The FPD 101 is a liquid crystal panel, a color filter substrate, a TFT array substrate or the like used for a liquid crystal display device. The FPD 101 is placed on a transparent glass stage (not shown) and observed. A transmitted image and a reflected image of the FPD 101 are measured by the CCD camera 115 to inspect for defects and foreign matters.

  First, an incident light source optical system for capturing a reflected image will be described. The light emitted from the incident light source 111 passes through the incident light source condenser lens 112 and is condensed. The light beam that has passed through the epi-illumination light source condenser lens 112 is irradiated onto the half mirror 113 and branched into two light beams.

  One of them is reflected by the half mirror 113 in the direction of the FPD 101. This light passes through the imaging lens 114 and illuminates the FPD 101. The light reflected by the FPD 101 passes through the half mirror 113 and enters the CCD camera 115. A reflected image is picked up by this light.

  A transmission light source 121 for capturing a transmission image is provided on the back side of the FPD 101. The light emitted from the transmissive light source 121 passes through the transmissive light source condenser lens 122 and is condensed. Then, the FPD 101 is illuminated.

  The light that has passed through the FPD 101 further passes through the half mirror 113. This light enters the CCD camera 115. A transmission image is picked up by this light. With these two light sources, a transmission image and a reflection image of the FPD 101 are captured, and the FPD 101 is inspected for defects and foreign matter.

  In order to inspect the entire surface of the FPD 101, it is necessary to move the FPD 101 or the optical system. However, when the FPD 101 is moved, there is a demerit that the apparatus size increases. Furthermore, this demerit becomes conspicuous as the substrate size increases in recent years.

  Therefore, in order to inspect the entire surface of the FPD 101, the FPD 101 is fixed and the optical system is moved as shown in FIG. 8 (see, for example, Patent Document 1). However, the inspection apparatus configured as described above has the following problems. It is necessary to illuminate the light from the incident light source 111 and the light from the transmissive light source 121 at the same position. In this case, the incident optical system 110 including the CCD camera 115 and the transmission optical system 120 must be moved while tracking. In this case, the drive system becomes complicated, and it is difficult to reduce the number of parts and reduce the cost. The FPD 101 is mounted on a transparent glass stage that transmits light. However, the glass stage is susceptible to vibration and may affect the inspection. Further, when the FPD 101 is directly supported by a non-transparent object, light cannot be transmitted, so that the earthquake resistance cannot be improved.

  In particular, since the substrate size of the liquid crystal display device has been increased in recent years, it is necessary to widen the driving range. Therefore, there is a problem that the component parts are increased in size and weight. In addition, it is necessary to improve the accuracy of the drive system due to recent miniaturization of the wiring pattern. In the configuration as described above, there is a problem that the drive system becomes complicated in order to move the two optical systems with high accuracy.

  An inspection apparatus having another configuration will be described with reference to FIG. FIG. 9 is a perspective view showing a configuration of a conventional inspection apparatus. Since the same reference numerals as those in FIG. 8 indicate the same configuration, the description thereof is omitted. Here, 126 is a fluorescent lamp, and 127 is a diffusion plate. In this inspection apparatus, the transmission light source and the transmission optical system of the above-described inspection apparatus are different.

  In this inspection apparatus, a fluorescent lamp 126 is used as a transmissive light source. This fluorescent lamp 126 is provided on the back side of the FPD 101. The light from the fluorescent lamp 126 is diffused by the diffusion plate 127 to illuminate the entire surface of the FPD 101 from the back side. With this configuration, the entire surface of the FPD 101 can be illuminated. Therefore, it is not necessary to move the transmission optical system 120, and the entire surface of the FPD 101 can be observed by moving only the epi-optical system 110.

  However, in this configuration, the illumination efficiency is extremely low, and it is necessary to increase the number of fluorescent lamps 126 in order to obtain a sufficient amount of light for inspection. Therefore, there is a problem that it is difficult to save power. In particular, since the substrate size of the liquid crystal display device has been increased in recent years, this problem becomes prominent.

  Further, although the light is diffused by the diffusion plate 127, it is difficult to uniformly illuminate the entire FPD, and there is a problem that the inspection accuracy is deteriorated due to a difference in brightness in the plane. Furthermore, since the light from the fluorescent lamp 126 that has passed through the diffusion plate 127 is used, it is difficult to control the coherence of illumination, that is, the partial coherence factor. Therefore, there is a problem that it is difficult to control resolution and contrast.

An image measuring machine is also disclosed in which a flat light emitter is provided on a mounting table on which an observation work is placed, and the work is placed thereon. However, this image measuring machine requires a light emission excitation source and its optical system. Moreover, since the fluorescence from the light emitter is used, it may be difficult to keep the light quantity constant.
JP 2001-305074 A JP 2002-207004 A

As described above, the conventional optical apparatus has a problem that the apparatus becomes complicated and large when a transmission image and a reflection image are captured and observed.
The present invention has been made in view of such problems, and an object thereof is to provide an optical apparatus, an imaging apparatus, and an inspection apparatus that can observe and capture a transmission image with a simplified optical system. .

  An optical device according to a first aspect of the present invention is an optical device that performs an operation related to a target object using light transmitted through a target object (for example, FPD1 according to the present embodiment), and includes a light source (for example, The incident light source 11) according to the present embodiment, first optical means for guiding light from the light source to the front surface of the target object (for example, the objective lens 14 according to the present embodiment), and the light source A filter (for example, the filter 20 according to the present embodiment) disposed between the target object and having a light shielding part that shields a central part and a light transmitting part provided around the light shielding part, and the target A retroreflective member (for example, a retroreflective sheet according to the present embodiment) that is disposed on the back side of the object and retroreflects light in the same direction as the incident direction, and is retroreflected by the retroreflective member, and the object Second optical means for receiving light transmitted (e.g., a camera 15 according to this embodiment) and is intended and a. Thereby, it is possible to accurately observe and capture the transmission image with a simple configuration.

  An optical device according to a second aspect of the present invention is the above-described optical device, wherein the light shielding unit corresponds to a region that is a field of view on the target object. Thereby, a transmission image can be picked up and observed more accurately with a simple configuration.

  An optical device according to a third aspect of the present invention is characterized in that, in the above-described optical device, the target object is placed separately from the retroreflective member. Thereby, it is possible to prevent the reflected light and the transmitted light from overlapping, and it is possible to accurately observe and capture the transmitted image with a simple configuration.

  An optical device according to a fourth aspect of the present invention is characterized in that, in the above-described optical device, the filter is provided so as to be able to be taken in and out of the optical path. Thereby, a transmission image and a reflection image can be observed and imaged separately with a simple configuration.

  An optical device according to a fifth aspect of the present invention is the above optical device, wherein the polarizing device is placed on the back side of the target object and changes the polarization state of light incident on the target object from the retroreflective member. And the second optical means changes the amount of the reflected light or the transmitted light based on a difference in polarization state between the received transmitted light and the reflected light reflected by the front surface of the target object. It is. Thereby, it is possible to accurately observe and capture the transmission image and the reflection image with a simple configuration.

  In the optical device according to a sixth aspect of the present invention, in the above-described optical device, the polarizing means is a quarter-wave plate that shifts the phase between the biaxial polarization components of incident light by a quarter wavelength. It is a feature. Thereby, it is possible to accurately observe and capture the transmitted image and the reflected image with a simple configuration.

  An imaging apparatus according to a seventh aspect of the present invention is an imaging apparatus that captures a transmission image of the target object using light transmitted through the target object, and includes a light source and light from the light source of the target object. A first optical means that guides light to the front surface, a filter that is disposed between the light source and the target object and that has a light shielding portion that shields a central portion and a light transmitting portion provided around the light shielding portion; A retroreflective member that is disposed on the back side of the target object and retroreflects light in the same direction as the incident direction; and an imaging unit that receives the transmitted light that is retroreflected by the retroreflective member and transmitted through the target object. Is provided. Thereby, a transmission image can be accurately picked up with a simple configuration.

  An imaging device according to an eighth aspect of the present invention is the imaging device described above, wherein the light shielding unit corresponds to a region that is a visual field on the target object. Thereby, a transmission image can be more accurately picked up with a simple configuration.

  An imaging apparatus according to a ninth aspect of the present invention is the above-described imaging apparatus, wherein the polarization unit is placed on the back side of the target object and changes the polarization state of light incident on the target object from the retroreflective member. When the filter is provided so that it can be taken in and out of the optical path, and when the filter is arranged on the optical path, the transmitted light is received by the imaging means, and when the filter is arranged outside the optical path The reflected light is separated based on the difference in polarization state between the transmitted light and the reflected light reflected by the front surface of the target object, and the reflected light is received by the imaging means. Thereby, it is possible to capture a transmission image and a reflection image with a simple configuration.

  An inspection apparatus according to a tenth aspect of the present invention is provided in the above-described imaging apparatus. Thereby, it is possible to perform an inspection using a transmission image with a simple configuration.

  In the present invention, the optical means includes a detector such as a CCD camera in addition to optical components such as a lens, a mirror, a prism, and a filter. Further, in the following description, when one element receives light from another element, it includes the case of receiving light via other optical means in addition to receiving light directly.

  According to the present invention, an optical apparatus, an imaging apparatus, and an inspection apparatus that can observe and capture a transmission image with a simple configuration are provided.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description is omitted and simplified as appropriate. Further, those skilled in the art will be able to easily change, add, and convert each element of the following embodiments within the scope of the present invention. In addition, what attached | subjected the same code | symbol in each figure has shown the same element, and abbreviate | omits description suitably.

  An inspection apparatus using the observation optical apparatus according to the present invention will be described with reference to FIG. FIG. 1 shows an inspection apparatus which is an example of an optical apparatus according to the present invention. 1 is an FPD, 11 is an incident light source, 12 is a condenser lens, 13 is a beam splitter, 14 is an objective lens, 15 is a camera, 16 is a polarizing plate, 19 is a polarizing plate on the camera side, 20 is a filter, 23 is a retroreflective sheet, Reference numeral 24 denotes a quarter wavelength plate, 41 denotes a relay lens, and 42 denotes a tube lens.

  The inspection apparatus shown in FIG. 1 is for inspecting a defect of the FPD 1 that is an inspection object, for example. The FPD 1 is a liquid crystal panel, a color filter substrate, a TFT array substrate, or the like used for a liquid crystal display device, and is assumed to be placed on an observation stage (not shown). The FPD 1 is formed with a transmission region that transmits light and a reflection region that reflects light according to the position. For example, in a color filter substrate, R, G, and B colored layers are transmissive regions that transmit part of light, and a black matrix (BM) is a reflective region that reflects light.

  In the inspection apparatus illustrated in FIG. 1, a reflected image reflected by the surface of the FPD 1 and a transmitted image transmitted by the FPD 1 that are reflected by the surface of the FPD 1 can be separately captured by one incident light source. An optical system for separately capturing a reflected image and a transmitted image will be described. In the present embodiment, it is assumed that the reflected light is reflected by the surface of the FPD 1, the reflected light is transmitted through the FPD 1, reflected by the retroreflective sheet 23, and again transmitted through the FPD 1. The transmitted light and the reflected light are separated by the camera side polarizing plate 19 based on the polarization state. This will be described.

  An epi-illumination light source 11 is provided at a position facing the FPD 1. The epi-illumination light source 11 is a general lamp light source, and examples thereof include a halogen lamp and a xenon lamp. The light from the epi-illumination light source 11 passes through the polarizing plate 16, so that components other than a certain vibration direction are cut. When natural light (unpolarized light) or circularly polarized light is incident on the polarizing plate 16, the polarizing plate 16 can polarize the natural light into linearly polarized light. Therefore, the natural light (unpolarized light beam) radiated from the incident light source 11 is polarized by the polarizing plate 16 into linearly polarized light having a certain polarization angle (vibration direction). The linearly polarized light polarized by the polarizing plate 16 passes through the condenser lens 12 and is condensed so as to obtain a necessary amount of light.

  The light condensed by the condenser lens 12 passes through the field stop and enters the relay lens 41a. The light collected by the relay lens 41a passes through the illumination stop and enters the relay lens 41b. The light collected by the relay lens 41 b enters the beam splitter 13. The condenser lens 12 and the relay lenses 41a and 41b are one or a plurality of optical lenses, and refract incident light to be emitted. A filter 20 is provided between the beam splitter 13 and the relay lens 41 so that it can be inserted. Here, the filter 20 is disposed outside the optical path. The filter 20 will be described later. The field stop position is between the condenser lens 12 and the relay lens 41a, and the illumination stop position is between the relay lens 41a and the relay lens 41b.

  Part of the light incident on the beam splitter 13 passes through the beam splitter 13 as it is and exits in the direction of the FPD 1. A coaxial illumination system is configured by branching the light from the incident light source 11 by the beam splitter 13. This coaxial illumination system can illuminate the plane efficiently without shadows. In the inspection apparatus according to the present embodiment, a transmission image based on the transmitted light transmitted through the FPD 1 with light from one incident light source 11 and a reflected image based on the reflected light reflected on the surface of the FPD 1 can be separately captured. . The light that has passed through the beam splitter 13 enters the tube lens 42. The tube lens 42 is composed of a plurality of lenses, and collects and emits incident light. The light incident on the tube lens 42 from the beam splitter 13 is refracted so as to be condensed and emitted in the direction of the FPD 1. The light from the tube lens 42 is collected by the objective lens 14 arranged to face the FPD 1 and enters the FPD 1. That is, the objective lens 14 refracts the incident light so that it becomes an appropriate spot on the FPD 1 and emits it in the direction of the FPD 1. The FPD 1 is placed on, for example, a hollow stage so that incident light is transmitted.

  Of the light incident on the FPD 1, the reflected light reflected on the surface of the FPD 1 is incident on the objective lens 14 again. The light incident on the objective lens 14 is refracted and emitted, and passes through the objective pupil. Then, the light passes through the tube lens 42 and enters the beam splitter 13. The beam splitter 13 reflects part of the light incident from the FPD 1 in the direction of the camera 15. The light reflected to the camera side enters the camera side polarizing plate 19. The camera-side polarizing plate 19 cuts light other than the component having a certain vibration direction, and the incident light is polarized into linearly polarized light. Further, the camera-side polarizing plate 19 can be rotated and can transmit only light in an arbitrary vibration direction. Therefore, when natural light (unpolarized light) or circularly polarized light is incident, it can be polarized into linearly polarized light. Furthermore, the polarization angle of linearly polarized light can be adjusted by rotating the camera-side polarizing plate 19.

  On the other hand, of the light incident on the FPD 1, the light transmitted through the FPD 1 is incident on the quarter wavelength plate 24. This is because, for example, the FPD 1 is placed on a stage in which a hole is formed in a portion irradiated with light from the incident light source 11 and illuminated. The quarter wavelength plate 24 can shift the phase between the biaxial polarization components of incident light by a quarter wavelength. Therefore, the vibration direction of linearly polarized light can be rotated by 90 degrees by passing the light twice. The light transmitted through the quarter wavelength plate 24 enters the retroreflective sheet 23. The light incident on the retroreflective sheet 23 is retroreflected in almost the same direction as the incident direction, and passes through the quarter wavelength plate 24 again. Therefore, the light that has passed through the FPD 1 has passed through the quarter-wave plate 24 twice. The light that has passed through the quarter-wave plate 24 enters the FPD 1. Light incident on the FPD 1 passes through the FPD 1. The transmitted light that has passed through the FPD 1 enters the camera-side polarizing plate 19 into the camera 15 in the same manner as the reflected light.

  The inspection apparatus according to the present invention can separate the reflected light and transmitted light by the camera side polarizing plate 19. Light from the incident light source 11 is irradiated to the FPD 1 by the polarizing plate 16 as linearly polarized light. Here, for example, it is assumed that light from the incident light source 11 is polarized into P-polarized light by the polarizing plate 16.

  When P-polarized light is incident on the FPD 1, the reflected light reflected by the surface of the FPD 1 becomes the same P-polarized light. On the other hand, the transmitted light that has been reflected by the retroreflective sheet 23 and transmitted again through the FPD 1 passes through the quarter-wave plate 24 provided on the back side of the FPD 1 twice, so that the polarization angle is shifted by 90 degrees. , S-polarized light. The reflected light and the transmitted light incident on the camera-side polarizing plate 19 have a 90-degree polarization angle different from each other. By rotating the camera-side polarizing plate 19 and adjusting the angle, transmitted light or reflected light can be selectively transmitted. When capturing a reflected image, the camera-side polarizing plate 19 is rotated so that light having the same polarization angle as the linearly polarized reflected light reflected by the FPD 1 is transmitted, and the mounting angle is adjusted. As a result, transmitted light whose polarization angle is 90 degrees different from each polarization of the camera-side polarizing plate 19 is cut, and only reflected light is incident on the camera 15.

  on the other hand. When the transmission image is captured, the camera-side polarizing plate 19 is rotated 90 degrees from the state where the reflected image is captured. Then, the reflected light having a polarization angle different from the polarization direction of the camera side polarizing plate 19 is cut. Accordingly, only the transmitted light having the same polarization angle as the polarization direction of the camera side polarizing plate 19 is transmitted through the camera side polarizing plate 19. Thereby, only the transmitted light is incident on the camera 15. Therefore, only transmitted light can be separated, and only a transmitted image can be captured. When the reflected image is captured, the transmitted light is cut by the camera side polarizing plate 19, and when the transmitted image is captured, the reflected light is cut by the camera side polarizing plate 19. Accordingly, only one of the reflected light and the transmitted light can be selectively transmitted and can be incident on the camera 15. Thereby, either the transmitted light or the reflected light is detected by the camera 15, and the transmitted image and the reflected image can be captured separately.

  That is, when the reflected image is captured, the transmitted light that is transmitted through the FPD 1 and reflected by the retroreflective sheet 23 and transmitted through the FPD 1 again is cut by the camera-side polarizing plate 19. Therefore, only the reflected light can be separated, and only the reflected image can be taken. On the other hand, when a transmission image is captured, the reflected light reflected by the surface of the FPD 1 is cut by the camera side polarizing plate 19. Therefore, only transmitted light can be separated, and only a transmitted image can be captured. In this way, by placing the quarter wavelength plate 24 on the back side of the FPD 1, the transmitted light and the reflected light become linearly polarized light orthogonal to each other, so that the camera-side polarizing plate 19 depends on the polarization angle. Each can be separated by rotating.

  Furthermore, in this embodiment, in order to capture a transmission image more accurately, the filter 20 is disposed between the relay lens 41b and the beam splitter 13 so as to be insertable. This will be described below.

  The light reflected on the surface of the FPD 1 may rotate due to dust adhering to the FPD 1 or the edge of the pattern provided on the FPD 1 (for example, the boundary between the colored layer and the BM). That is, when light is irradiated to the part where the dust on the FPD 1 adheres or the boundary between the colored layer and the BM, the polarization state changes when passing through the FPD 1. In this case, for example, the reflected light reflected by the surface of the FPD 1 does not become completely P-polarized light but enters the camera-side polarizing plate 19. As a result, the reflected light and the transmitted light do not become linearly polarized light having an orthogonal polarization angle, and the other light is incident on the camera 15 when one of the images is captured. Thereby, for example, a reflection image may be captured although a transmission image is supposed to be captured. In the present embodiment, in order to prevent this, a transmission image is picked up with the filter 20 inserted in the optical path as shown in FIG.

  A configuration of the filter 20 for accurately capturing a transmission image will be described with reference to FIG. FIG. 3 is a diagram showing the configuration of the filter 20. The filter 20 is provided with a circular light shielding portion 21 at the center, and an opening 22 is provided around it. The light incident on the light shielding part 21 is shielded and the light incident on the opening part 22 is transmitted as it is. Further, the periphery of the opening 22 is shielded from light. The light shielding portion 21 is inserted so that the center of the light shielding portion 21 overlaps the optical axis. The filter 20 is inserted perpendicular to the optical axis of the inspection apparatus. By disposing the filter 20 on the optical path, the optical axis and the surrounding light are shielded, and the ring-shaped light enters the FPD 1. The FPD 1 is illuminated with light transmitted through the opening 22 around the light shielding portion 21. Therefore, the FPD 1 is illuminated in a ring shape. The filter 20 can be formed, for example, by patterning a light shielding film on a transparent glass substrate by a photolithography process. Alternatively, the opening 22 may be mechanically provided. In this case, the light shielding part 21 is fixed by a bridge or the like.

  The light shielding portion 21 is formed with a size corresponding to the visual field in the FPD 1. That is, a part corresponding to the light shielding unit 21 is imaged by the camera 15. At the time of transmission image capturing, the portion of the visual field is not illuminated, and only the periphery thereof is illuminated in a ring shape by the light from the opening 22. FIG. 4 shows the configuration of the FPD 1 illuminated in the ring shape. FIG. 4 is a cross-sectional view showing a configuration of the FPD 1 illuminated in a ring shape. In FIG. 4, the quarter wavelength plate 24 is omitted. By disposing the filter 20 in alignment with the optical axis, the FPD 1 can have a non-illuminating portion 28 and an illuminating portion 27. The central non-illuminated portion 28 is at a position corresponding to the visual field, and this portion is imaged by the camera 15. A ring-shaped illumination unit 27 is disposed around the non-illumination unit 28 corresponding to the visual field. The non-illuminating unit 28 corresponds to the light shielding unit 21, and the illuminating unit 27 corresponds to the opening 22.

  Since the light shielding part 21 is provided so that the non-illuminating part 28 becomes the field of view, the size of the light shielding part 21 projected onto the FPD 1 is, for example, about 100 μm to 1 mm. The surrounding opening 22 is, for example, made to have a width of 1/10 to 1/3 of the size of the light shielding part 21. When the magnification of the objective lens 14 is high, the field of view is small, and when the magnification is low, the field of view is large. The actual dimensions of the light shielding portion 21 and the opening 22 in the filter 20 are determined based on the magnification of the lens and the like.

  In the light incident on the FPD 1 from the objective lens 14, the field of view becomes the non-illumination unit 28, and the outside of the field of view becomes the illumination unit 27. That is, the non-illuminating unit 28 is imaged by the camera 15. Therefore, the reflected light reflected by the surface of the FPD 1 in the illumination unit 27 does not contribute to the imaging with the camera 15. In the illumination unit 27, the light that has passed through the opening 22 of the filter 20 and entered the illumination unit 27 passes through the FPD 1 and enters the retroreflective sheet 23.

  FIG. 4 schematically shows a light beam collected by the objective lens 14 and incident on a point of the non-illumination unit 27 in the FPD 1 with an arrow. The light beam incident on the objective lens 14 is collected at one point in the non-illuminating portion 27 of the FPD 1. Here, most of the light incident on the retroreflective sheet 23 is reflected in the same direction as the incident direction, but a part of the light is reflected in a direction different from the incident direction as shown in FIG. An arrow in the vicinity of the optical axis in the objective lens 14 indicates light reflected in a direction different from the incident direction. That is, in the vicinity of the optical axis of the objective lens 14, the light incident in the direction of the arrow is reflected by the retroreflective sheet 23 in a direction different from the incident direction. This will be described later. In the present invention, the retroreflective sheet 23 illuminates the field of view using light reflected in a direction different from the incident direction. The light incident on the illumination unit 27 illuminates the non-illumination unit 28 that is the field of view from the back side of the FPD 1.

  A part of the light reflected by the retroreflective sheet 23 in the direction different from the incident direction is reflected in the direction of the visual field portion that is the non-illuminated portion 28. For example, a 10 mm gap is provided between the retroreflective sheet 23 and the FPD 1. Thereby, the light reflected in the direction of the visual field portion by the retroreflective sheet 23 enters the visual field portion. The light transmitted through this visual field portion is detected by the camera 15 as described above. Therefore, the visual field portion that is the non-illuminating portion 28 can be illuminated with the transmitted light. In addition, since there is no light incident directly from the incident light source 11 in the field of view, the reflected light is not detected by the camera 15. Thereby, only the transmitted light can be incident on the camera 15. By providing the filter 20 in this way, a transmission image can be accurately captured.

  Next, a phenomenon in which the retroreflective sheet 23 is reflected in a direction different from the incident direction will be described with reference to FIG. Fig.5 (a) is an expanded sectional view which shows typically the structure of a bead type retroreflection sheet. FIG. 5B is an enlarged cross-sectional view schematically showing the configuration of a prism type retroreflective sheet. First, the principle of retroreflection on the bead type retroreflection sheet 23 will be described with reference to FIG.

  FIG. 5A shows an example of the retroreflective sheet 23 using the glass beads 31. Further, in FIG. 5A, the retroreflected light 51 accurately retroreflected by the glass beads and the light 52 reflected in a direction different from the incident direction are indicated by arrows.

  A large number of glass beads 31 are scattered on the retroreflective sheet 23. For example, minute spherical glass beads 31 having a diameter of several tens of μm are provided on the reflective layer 32. The glass beads 31 refract incident light due to a difference in refractive index. The reflective layer 32 is a hemispherical recess corresponding to the glass bead 31. The surface of the reflective layer 32 is, for example, a reflective surface that reflects light by Al deposition or the like. Glass beads 31 are provided in this recess. A large number of such glass beads 31 and reflective layers 32 are provided on a sheet serving as a substrate. Furthermore, a surface film may be provided thereon. With the configuration described above, light incident from the direction of the arrow is refracted by the glass beads 31 and reflected by the reflective layer 32. The light reflected by the reflective layer 32 is refracted by the glass beads 31 and reflected in the direction of the arrow. That is, it is reflected in the same direction as the incident direction, like retroreflected light 51 that is accurately retroreflected in FIG. In this way, the light incident on the retroreflective sheet 23 is retroreflected in the same direction as the incident direction.

  However, for example, the retroreflected light may not be accurately reflected due to a shift in the shape of the glass beads 31 or the reflective layer 32. That is, when the glass beads and the reflection layer 32 are not perfectly spherical, the incident direction and the reflection direction do not exactly match. In this case, the incident direction is different from the reflecting direction, and the incident light is reflected in a direction different from the incident direction, as indicated by the light 52 in FIG. The light reflected in a direction different from the incident direction is reflected at a position different from the incident position on the FPD 1. Such deviation between the incident direction and the reflection direction is due to errors in the production of glass beads and reflective layers, errors during glass bead attachment, dust adhering to the surface, surface film, etc. Various factors such as deterioration can be considered. Therefore, it is practically difficult for the retroreflective sheet 23 to completely retroreflect all the light, and a part of the light is reflected in a direction different from the incident direction. The field of view corresponding to the light shielding unit 21 is illuminated using light reflected in a direction different from the incident direction.

  In addition, spherical lenses generally have spherical aberration. Therefore, spherical aberration also exists in the glass beads 31 used for the bead type retroreflective sheet 23. Therefore, the reflected light reflected on the surface of the retroreflective sheet 23 is not necessarily reflected in the same direction as the incident light. The angle of the reflected light varies depending on the incident height h, which is the height from the optical axis (the central axis of the glass beads 31). Thereby, the light 52 reflected in a direction different from the incident light is generated. In particular, light with a high incident height h has large spherical aberration and is reflected in a direction different from the incident direction. The field of view corresponding to the light shielding unit 21 is illuminated using light reflected in a direction different from the incident direction.

  FIG. 5B shows an example of a prism type retroreflective sheet 23. The prism type retroreflective sheet 23 will be described. An adhesive 34 is provided on the substrate 35. A prism sheet provided with a large number of microprisms 33 is bonded onto the adhesive 34. As a result, the prism sheet is attached onto the substrate 35. The microprism 33 is formed of a transparent resin such as acrylic. As shown in FIG. 5B, the light incident on the microprism 33 refracts the incident light due to the difference in refractive index and reflects it in the same direction as the incident direction.

  In the microprism 33, the angle deviation of the slope is emphasized as shown below, and the angle deviation of the reflected light is caused. This will be described with reference to FIG. FIG. 5C is a diagram showing the traveling direction of light in the prism. The inclination between the normal 57 of the mirror surface 56 of the microprism 33 and the incident light 53 incident on the mirror surface 56 of the microprism 33 is defined as θ. The angle between the perpendicular of the incident light 53 and the mirror surface 56 is also θ. Furthermore, the angle between the normal 57 of the mirror surface 56 and the reflected light 54 reflected by the mirror surface 56 is also θ. The angle between the incident light 53 and the reflected light 54 is 2θ. The inclination θ of the mirror surface 56 is enlarged to 2θ by reflected light. Therefore, when the actual prism angle deviates from the design value and an error occurs in the mirror surface 56, the reflected light error is also doubled.

  The light incident on the inside of the microprism 33 is reflected by the two mirror surfaces as shown in FIG. That is, since the retroreflective sheet 23 has two reflecting surfaces, four times the specular error (error from the true angle) becomes the reflected light error.

  Here, it is assumed that a 10 mm gap is provided between the retroreflective sheet 23 and the FPD 1. For example, in the case of a 50 × objective lens, the field of view is about 400 μmφ. In this example, if there is an angle error of 200 μm (radius) / 10 mm (distance) = 20 mrad between the incident light and the reflected light, the light transmitted through the illumination unit 27 can illuminate the illumination unit. That is, in the light reflected by the retroreflective sheet 23, if there is an optical axis error of 20 mrad, the illumination unit 27 and the ambient light transmitted therethrough can illuminate the central part that is the non-illumination unit 28. Since the optical axis error of the reflected light is enhanced by four times the specular error due to the specular reflection of the two surfaces, if there is a specular error of 20 mrad / 2/2 = 5 mrad, the non-illuminated portion is caused by the light transmitted through the illumination unit 27. 28 can be illuminated. A minute error of about 5 mrad is an angle error generated in a general prism type retroreflective sheet 23. Further, d in FIG. 5B is also involved, and the reflected light is more diffused.

  The retroreflective sheet 23 shown in FIG. 5 is a typical example, and the retroreflective sheet that can be used in the present invention is not limited thereto.

  As described above, accurate retroreflection may not be achieved due to a deviation in the shape of the glass beads 31, the reflective layer 32, or the microprism 33, or spherical aberration. In other words, the incident direction and the reflection direction do not exactly match at locations where the glass beads 31 and the reflective layer 32 are not perfectly spherical or where the angle of the inclined surface of the microprism 33 is shifted. The light incident on such a location is reflected in a direction different from the incident direction because the incident direction and the reflecting direction are shifted. The light reflected in a direction different from the incident direction is reflected at a position different from the incident position on the FPD 1. Such misalignment between the incident direction and the reflection direction includes errors in manufacturing the glass beads 31, the reflective layer 32, or the microprism 33, aberrations, errors in attaching the glass beads or the microprism 33, and dust or foreign matters attached to the surface. Various factors such as a shift of the surface film and the deterioration of the retroreflective sheet with time can be considered. Therefore, it is practically difficult for the retroreflective sheet 23 to completely retroreflect all the light, and a part of the light is reflected in a direction different from the incident direction. The field of view corresponding to the light shielding unit 21 is illuminated using light reflected in a direction different from the incident direction.

  The non-illuminated part 28 that could not be directly illuminated as described above can be illuminated by the light reflected in a direction different from the incident direction. That is, as shown in FIG. 4, in the FPD 1, a part of the light incident on the illumination unit 27 changes in angle, and a part of the light is reflected toward the non-illumination unit 28. Therefore, the light reflected by the retroreflective sheet 23 enters the non-illuminating unit 28 and passes through the visual field portion of the FPD 1. In FIG. 4, only light near the optical axis is reflected in a direction different from the incident direction, but other light is also reflected in a direction different from the incident direction. A part of the light reflected in a direction different from the incident direction is incident on the non-illuminating unit 28 and is transmitted through the visual field portion. By detecting this light with the camera 15, a transmission image can be accurately taken. Furthermore, since the distance between the FPD 1 and the retroreflective sheet 23 is increased by installing the FPD 1 apart from the retroreflective sheet 23, even if there is little light reflected in a direction different from the incident direction, the FPD 1 is not efficiently The illumination unit 28 can be illuminated. In the present embodiment, for example, a 10 mm gap is provided between the retroreflective sheet 23 and the FPD 1.

  When a transmission image is captured, the filter 20 is inserted on the optical path as shown in FIG. By inserting the filter 20, the field of view becomes a non-illuminated part, so that the reflected light is not detected by the camera 15. Therefore, as shown in FIG. 2, the camera-side polarizing plate 19 disposed in front of the camera 15 may be removed from the optical path when a transmission image is captured. That is, the camera side polarizing plate 19 and the filter 20 are provided so as to be able to be taken in and out of the optical path, and when the transmission image is captured, the filter 20 is arranged on the optical path, and the camera side polarizing plate 19 is arranged outside the optical path. When capturing a reflected image, the filter 20 is disposed outside the optical path, and the camera-side polarizing plate 19 is disposed on the optical path. Then, the camera-side polarizing plate 19 is rotated so that the transmitted light is shielded. Thereby, a reflected image and a transmitted image can be captured separately. Furthermore, a transmission image can be taken more accurately.

  The filter 20 is arranged at the real image position, that is, the position of the primary image or the position of the field stop. Specifically, it is arranged at an image forming position between the relay lens 41b and the beam splitter 13 or an image forming position between the condenser lens 12 and the relay lens 41a. As a result, it is possible to prevent the light in the field of view from entering and to accurately capture the transmission image.

  The reflected or transmitted image captured by the camera 15 is output by a processing device connected to the camera 15. In a processing apparatus using a personal computer or the like, the presence or absence of a defect is determined by comparing the reference pattern and the imaging pattern. Since these processes can use normal processes, description thereof is omitted.

  In the above-described embodiment, the CCD camera is used as the image pickup means. However, an individual image pickup device such as a MOS or CMOS, a photodiode array, or the like may be used. Furthermore, an eyepiece can be provided instead of the imaging means, and the present invention can be applied to an observation apparatus and a microscope for observing an object to be observed with the naked eye. Even in such an observation apparatus and microscope, it is not necessary to provide a transmission-side illumination system, which leads to cost reduction. Of course, inspection, imaging, observation, and the like may be performed using objects other than the FPD 1 as target objects.

  The incident light source 11 may be a light source that can obtain a necessary amount of light, and examples thereof include a halogen lamp and a xenon lamp. In addition, a laser, LED, fluorescent lamp, light bulb, or the like may be used. Of course, the wavelength of light is not specified, and white light or a light source that emits light of a specific wavelength may be used. Moreover, it is not restricted to visible light, It can be used also with the light source which radiates | emits light other than visible light, such as infrared rays and an ultraviolet-ray, with a measuring instrument.

  In the inspection apparatus described above, the light from the incident light source 11 is polarized into linearly polarized light using the polarizing plate 16, but a polarizing element such as a polarizing beam splitter may be used. Furthermore, a polarized light source may be used as the incident light source 11. Of course, the present invention can be used for an optical apparatus having a configuration other than the illustrated configuration. For example, two imaging devices may be provided, and a transmission image and a reflection image may be captured by separate imaging devices. Furthermore, according to the present invention, a transmission image and a reflection image can be separately captured by one light source, and a transmission image can be captured more accurately. Further, by removing the camera-side polarizing plate 19, an image obtained by superimposing the reflected image and the transmitted image can be taken. Since a transparent glass stage is not necessary, the apparatus configuration can be simplified.

It is a figure which shows the structure of the test | inspection apparatus concerning this invention. It is a figure which shows the structure at the time of the transmission image imaging of the inspection apparatus concerning this invention. It is a figure which shows the structure of the filter used for the defect inspection apparatus concerning this invention. It is sectional drawing which shows the structure of FPD at the time of the transmission image imaging of the inspection apparatus concerning this invention. It is a figure which shows the structure of a retroreflection sheet, and the advancing direction of light. It is a top view which shows the structure of the conventional inspection apparatus. It is a perspective view which shows the mode of the movement of the optical system in the conventional inspection apparatus. It is a perspective view which shows the structure of the conventional inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 FPD, 11 Incident light source, 12 Condenser lens, 13 Half mirror 14 Objective lens, 15 Camera, 16 Polarizing plate, 19 Camera side polarizing plate 20 Filter, 21 Light-shielding part, 22 Opening part, 23 Retroreflective sheet,
24 1/4 wavelength plate, 27 illumination part, 28 non-illumination part,
31 Glass beads, 32 Reflective layer, 41 Relay lens, 42 Tube lens 101 FPD, 110 Epi-illumination optical system, 111 Epi-illumination light source 112 Condenser lens for epi-illumination light source, 113 Half mirror, 114 Imaging lens 115 CCD camera, 120 Transmission optical system, 121 transmitted light source,
122 Condenser lens for transmission light source, 126 Fluorescent lamp, 127 Diffuser

Claims (10)

An optical device that performs operations related to the target object using light transmitted through the target object,
A light source;
First optical means for guiding light from a light source to the front surface of the target object;
A filter that is disposed between the light source and the target object and includes a light-shielding part that shields a central part and a light-transmitting part provided around the light-shielding part;
A retroreflective member disposed on the back side of the target object and retroreflects light in the same direction as the incident direction;
An optical apparatus comprising: a second optical unit that receives the transmitted light that is retroreflected by the retroreflective member and transmitted through the target object.   The optical device according to claim 1, wherein the light shielding unit corresponds to a region to be a visual field on the target object.   The optical apparatus according to claim 1, wherein the target object is placed separately from the retroreflective member.   4. The optical apparatus according to claim 1, wherein the filter is provided so as to be able to be taken in and out of the optical path. A polarization unit mounted on the back side of the target object and changing a polarization state of light incident on the target object from the retroreflective member;
The said 2nd optical means changes the light quantity of the said reflected light or the said transmitted light based on the difference in the polarization state of the received transmitted light and the reflected light reflected by the front surface of the said target object. Optical device.   6. The optical apparatus according to claim 4, wherein the polarizing means is a quarter wavelength plate that shifts the phase between the biaxial polarization components of incident light by a quarter wavelength. An imaging device that captures a transmission image of the target object using light transmitted through the target object,
A light source;
First optical means for guiding light from a light source to the front surface of the target object;
A filter that is disposed between the light source and the target object and includes a light-shielding part that shields a central part and a light-transmitting part provided around the light-shielding part;
A retroreflective member disposed on the back side of the target object and retroreflects light in the same direction as the incident direction;
An imaging apparatus comprising: imaging means for receiving transmitted light that is retroreflected by the retroreflective member and transmitted through the target object.   The imaging apparatus according to claim 1, wherein the light shielding unit corresponds to a region that becomes a visual field on the target object. A polarization unit mounted on the back side of the target object and changing a polarization state of light incident on the target object from the retroreflective member;
The filter is provided so that it can be taken in and out of the optical path,
When the filter is disposed on the optical path, the imaging means receives the transmitted light,
When the filter is disposed outside the optical path, the reflected light is separated based on a difference in polarization state between the transmitted light and the reflected light reflected from the front surface of the target object, and the reflected light is imaged. The imaging device according to claim 7 or 8, wherein the imaging device receives light by means. The inspection apparatus provided with the imaging device in any one of Claims 7 thru | or 9.

Images