Illumination device for inspection, illumination optical system, and inspection system

Abstract

To solve the problem that: object light returned from an inspection object irradiated with light consists of direct light and scattered light; the direct light cannot quantitatively capture change in light physical properties of the inspection object unless a solid angle element determined from a relative relationship between an irradiation solid angle and an observation solid angle is uniformly; and it is necessary to reduce both the irradiation solid angle and the observation solid angle in order to capture slight change in a surface shape, but the object light itself cannot be captured when an inspection surface is inclined.SOLUTION: In response to this, even when an irradiation solid angle and an observation solid angle are set to be small, object light can be captured up to a certain inclination of an inspection surface while detection sensitivity with respect to an inclination of an inspection target is kept constant. Specifically, a solid angle element is made constant, a plurality of annular solid angle regions are concentrically formed in an irradiation solid angle, the inclination is converted into light and dark information with same sensitivity even when the inspection target is a curved surface, minute unevenness can be detected without directional dependency up to the certain inclination of the inspection target, and minute change in light physical properties can be quantitatively imaged.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inspection lighting device, an illumination optical system, and an inspection system used for irradiating a test object with inspection light and inspecting the appearance, scratches, defects, etc. of the product.

Background Art

[0002] As an example of an inspection lighting device used for product appearance inspection, etc., there is coaxial illumination in which the imaging direction and the direction of illuminating the inspection object are made to coincide as shown in Patent Document 1. This coaxial illumination includes a light source that emits inspection light in a direction parallel to the inspection target surface of the inspection target, the inspection target, and a half mirror that is provided inclined between the inspection target and an imaging device provided above the inspection target, and is arranged such that the inspection light is reflected to the inspection target and the reflected light from the inspection target is transmitted to the imaging device side.

[0003] Coaxial illumination can make the irradiation direction of the irradiation light and the observation direction of the object light returned from the inspection object substantially coincide with respect to the inspection object, and can set the irradiation conditions and observation conditions substantially uniformly for each point of the inspection object, and has the effect of making it easy to capture changes in the optical properties of each point of the inspection object as changes in the object light radiated from each point of the inspection object. However, even so, in order to detect and capture changes in the optical properties due to minute defects in the inspection object, further improvements have been made according to Patent Documents 1, 2, 3, and 4 because it is necessary to set the irradiation conditions and observation conditions more uniformly at each point.

[0004] By the way, in recent years, there has been a demand to be able to detect feature points such as defects that are difficult to detect even when using the inspection lighting device as described above, based on the captured image. More specifically, the surface property of the product to be inspected is not only a completely matte surface that returns scattered light showing the same level of brightness regardless of the observation direction as object light, but also a feature point of the inspection target surface that returns direct light such as specular reflection light and specular transmission light with significantly different brightnesses depending on the irradiation direction of the inspection light and the observation direction of the object light, such as a glossy surface or a metal surface. In order to obtain the desired gradation information at such a feature point, it is difficult to precisely control the irradiation optical axis, the shape of the irradiation solid angle, etc. of the inspection light. Even if the inspection light can be irradiated, the observation direction of the object light changes depending on the position of the feature point on the inspection target, and as a result, the brightness difference changes greatly, and there are cases where it is difficult to discriminate the feature point.

[0005] More specifically, even if the reflection direction of the irradiated inspection light changes slightly due to minute defects or the like on the inspection target, if the change is within the observation solid angle of the imaging device, there will be no change in the brightness of the captured image regardless of the presence or absence of the defect. Or, if the irradiation solid angle of the inspection light is large and the inclination of its optical axis is different at each point of the inspection target, not only will a slight change in the reflection direction not be captured as a change in the amount of light within the observation solid angle of the imaging device, but also the change in the amount of light within the observation solid angle of the imaging device will vary at each point of the inspection target, and ultimately, such minute defects or the like cannot be accurately captured within the inspection target range as machine vision.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made in view of the above-described problems. Even if the characteristic points such as defects are extremely small or minute, and even if the change in reflection or scattering occurring at the characteristic points is slight, at each point in the imaging range of the inspection target, regardless of where the characteristic point is in the field of view, the light quantity within the observation solid angle of the imaging device can be changed by a certain amount. As a result, an inspection illumination device, an illumination optical system, and an inspection system capable of detecting the details of such minute characteristic points are provided.

[0008] Even if the characteristic points such as defects are extremely small or minute, and even if the change in reflection or scattering occurring at the characteristic points is slight, and also at each point in the imaging range of the inspection target, regardless of where the characteristic point is in the field of view, for example, the irradiation solid angle of the irradiation light with respect to each point of the inspection target and the observation solid angle formed by the imaging device that observes the object light returned from the inspection target are in the specular reflection direction with respect to each other. Due to the change in the optical properties such as the reflection direction at the characteristic point, a change in the radiant energy of the object light itself such as reflection or scattering returned from the object, reflecting the irradiation solid angle, or a change in the relative relationship between the solid angle of the object light and the observation solid angle occurs, and the light energy of the object light captured within the observation solid angle changes. As a result, the characteristic point can be detected as the luminance difference of the object light. However, the amount of change in the luminance of this object light is greatly influenced by the change amount of the relative relationship between the solid angle of the object light reflecting the irradiation solid angle and the observation solid angle that captures the object light, such as the respective magnitudes and the relative angle.

[0009] More specifically, when either the solid angle of the object light or the observation solid angle is completely included in the other, there is no luminance change due to the change in the relative relationship between the two solid angles. Or, when the solid angle of the object light and the observation solid angle do not have a part that includes each other, the brightness of the object light cannot be detected within the observation solid angle. Or, when the solid angle of the object light and the observation solid angle are large, the change in the brightness of the object light with respect to the change in the solid angle of the object light becomes relatively small, and there is a problem that it becomes difficult to detect the feature point.

[0010] In particular, when the inspection object is composed of a curved surface, depending on the position of the feature point on the curved surface, the magnitude of each of the solid angle of the object light reflecting the solid angle of the irradiation light and the observation solid angle for capturing the object light, and the relative relationship such as the relative angle change. Even for the same feature point, the amount of change in the brightness of the object light may increase or decrease. Furthermore, when the change in the inclination of the solid angle of the object light due to the feature point is small, it is necessary to set both the irradiation solid angle and the observation solid angle small so that the change in the inclination of the solid angle of the object light results in a larger change in brightness. However, in this case, if the surface of the inspection object is inclined by an angle greater than half of the sum of the plane half-angles of the irradiation solid angle and the observation solid angle, the object light caused by reflection cannot be captured within the observation solid angle, and the change in the solid angle of the object light due to the feature point within that surface cannot be detected either.

[0011] As described above, the present invention solves the problem that the amount of change in the relative relationship between the solid angle of the object light reflecting the irradiation solid angle and the observation solid angle of the imaging device causes a small change in the brightness of the object light due to the change in the light energy captured within the observation solid angle depending on the inclination of the surface of the inspection object, or that the change in brightness cannot be captured. As a result, an inspection lighting device, an illumination optical system, and an inspection system that can detect the details of such minute feature points are provided.

Means for Solving the Problem

[0012] The present invention makes the magnitude, shape, inclination, etc. of the irradiation solid angle of the inspection light emitted from the inspection lighting device and the illumination optical system uniform for each point of the inspection object, and arbitrarily divides and irradiates change elements other than the light propagation direction within the irradiation solid angle, such as different wavelengths, polarization planes, or light amounts, and moreover, by being able to adjust this, even if the defects, etc. in the inspection object are minute and the amount of change in reflection or scattering due to the defects, etc. is extremely small, within the observation solid angle formed by the imaging device, it can be captured as the change in the light amount for each region of different wavelength bands, polarization planes, or light amounts that are divided, and an image using this change as light and dark information can be obtained. It is made based on a novel idea of achieving this.

[0013] More specifically, the inspection lighting device and the illumination optical system of the present invention are an inspection lighting device and an illumination optical system that irradiate the inspection object with inspection light, and are applied to an inspection system including an observation optical system that captures the light reflected, transmitted, or scattered by the inspection object. In the inspection lighting device and the illumination optical system, a surface light source that emits inspection light, a lens provided between the surface light source and the inspection object for forming an irradiation solid angle with respect to the inspection object as the inspection light that irradiates the inspection object with the light radiated from the surface light source, and a first light shielding mask provided before and after the focus position of the lens with the focus position of the lens as the center, which shields and forms the irradiation solid angle of the inspection light irradiated to each point of the inspection object, and the first light shielding mask is provided with a plurality of annular solid angle regions that are concentrically arranged within the irradiation solid angle and have no adjacent portions to each other. The inspection lighting device and the illumination optical system can simultaneously form the same irradiation solid angle regardless of the distance from the inspection lighting device, the illumination optical system, and the lens to the inspection object and the position of each point of the inspection object, and the irradiation solid angle can be set to have the same relative angle simultaneously with respect to the observation solid angle for each point of the inspection object formed when the imaging device captures the light from the inspection object through the observation optical system.

[0014] Further, the inspection illumination device and the illumination optical system of the present invention may further include first filter means that, adjacent to the first light-shielding mask, divides the inspection light into arbitrary solid angle regions having partially different light attributes with light in different wavelength bands, different polarization planes, or light having different light amounts, or is set such that the light attributes change continuously. Further, the first light-shielding mask and the first filter means may be a third filter means unified as a means for forming a solid angle region and an irradiation solid angle, having at least any one of their functions.

[0015] Also, between the first light-shielding mask and the surface light source, near the position where the lens forms an image with respect to the inspection object, at least one of a second light-shielding mask and fourth filter means that transmits only light having a specific attribute is further provided. The irradiation region and irradiation pattern of the inspection light with respect to the inspection object may be arbitrarily generated by the second light-shielding mask or the fourth filter means. The second light-shielding mask and the fourth filter means that transmits only light having a specific attribute may be a fifth filter means having at least any one of the functions of the second light-shielding mask and the fourth filter means.

[0016] Further, the first light-shielding mask, the first filter means, and the third filter means may be disposed between the surface light source and the relay optical system (e.g., lenses arranged in tandem), and a relay image formed by the relay optical system may be used instead of the first light-shielding mask, the first filter means, and the third filter means. The relay image is a reduced image of the first light-shielding mask, the first filter means, and the third filter means. Note that the positions of the first light-shielding mask, the first filter means, and the third filter means may also be changeable along the illumination optical path (i.e., a configuration in which the relay image of the first light-shielding mask, the first filter means, and the third filter means can be disposed near the focal position of the lens). Also, the light-shielding mask may be a means for completely shielding light, may have a certain low transmittance, or may have a light attribute such that light does not pass through or has a transmittance lower than a certain level by the sixth filter means on the imaging device side. The first light-shielding mask, the first filter means, and the third filter means are of a transmissive type, but may be of a reflective type.

[0017] By the way, the brightness of each point of the inspection object is determined by the light energy captured within the observation solid angle formed at each point, and the amount of this light energy is determined by the light energy included in the included portion of the solid angle formed by the light reflected, transmitted, or scattered from each point, which is generated by the irradiation solid angle for each point, and the observation solid angle. When the light returned from each point is direct light such as specularly reflected light or directly transmitted light, the solid angle of the direct light is the same as the shape and size of the irradiation solid angle. When it is scattered light, the light energy determined by the spectral irradiance near each point is evenly radiated with respect to the entire observable solid angle.

[0018] When the light returned from each point of the inspection target is scattered light, the illuminance of each point is determined by the relative angle with the irradiation solid angle according to the inclination of the surface near each point of the inspection target. The radiant energy with respect to the total solid angle of the scattered light changes in proportion to the illuminance, and since this is captured by the observation solid angle and the brightness of each point changes, in order to detect a more minute inclination near each point of the inspection target, it is necessary to set the irradiation solid angle to be small so that the illuminance changes more greatly due to that minute inclination.

[0019] Also, when the light returned from each point of the inspection target is direct light, if the inclination of the solid angle of the direct light having the same shape as the irradiation solid angle changes due to the inclination of the surface near each point of the inspection target, and as a result, the inclusion relationship with the observation solid angle changes, the brightness of each point changes in conjunction with the inclination of the surface near each point. However, with respect to the sizes of the irradiation solid angle and the observation solid angle, if the inclination of the surface near each point is small, the amount of change in the brightness becomes small. Therefore, in order to detect a more minute inclination near each point of the inspection target, it is necessary to set the irradiation solid angle and the observation solid angle to be small so that the size of the included portion of the solid angle of the direct light and the solid angle of the observation light changes due to that minute inclination.

[0020] Here, even if the irradiation solid angle is made small, when the light returned from each point of the inspection target is scattered light, since the light radiated from each point of the inspection target is radiated evenly over the total solid angle, even if the surface near each point is greatly inclined, as long as it is within the range where the irradiation solid angle is formed, the change in illuminance can be detected as the brightness of the scattered light. However, when the light returned from each point of the inspection target is direct light, the solid angle of the direct light also becomes small, and the angular range within which the light energy can be captured by the observation solid angle becomes small. When the inclination of the surface near each point becomes larger than the range that can be captured by the observation solid angle, the light energy of the direct light cannot be captured, and the magnitude of the inclination of the surface near each point of the inspection target that can be observed is limited.

[0021] Therefore, in the case of such an inspection lighting device and an illumination optical system, even if the inclination of the surface near each point of the inspection target is minute, by appropriately setting the change in the inclusion relationship between the annular solid angle region and the observation solid angle, the minute inclination can be expressed as a change in the observation luminance of each point. Up to the angle determined by the outermost contour of the irradiation solid angle, even if the inclination of the surface near each point is large, the minute change in the inclination of the surface can be detected with the same detection sensitivity.

[0022] In other words, At each point of the inspection target, while maintaining the change in the relative relationship between the annular solid angle region formed within the irradiation solid angle and the observation solid angle, up to the range of inclination determined by the outermost contour of the irradiation solid angle, even if the inclination of the surface near each point of the inspection target is large, the minute change in the inclination from that inclination can be detected. Particularly when the inspection target is a curved surface, hitherto, when detecting a minute change in the inclination, the detection range has been limited, but now the detection range that can be imaged at one time can be made larger.

[0023] Furthermore, even when the intensity or direction of the reflected light, transmitted light, or scattered light slightly changes due to minute defects or the like in the inspection target, the irradiation solid angle shape and its angle of the inspection light irradiated to each point of the inspection target are appropriately set by the first light shielding mask or the first filter means so that a change occurs in the light quantity for each solid angle region having a different light attribute within the observation solid angle of the imaging device due to the changing portion. It can be appropriately set in accordance with the relative relationship with the size, shape, and angle of the observation solid angle of the imaging device and in accordance with the surface properties of the feature points on the object surface, making it easier to detect minute defects or the like, or conversely, making them undetectable.

[0024] In addition, it is possible to form irradiation solid angles in various modes, and by forming the solid angle regions having different light attributes inside the irradiation solid angle, it is possible to prevent the reflected light and transmitted light in the inspection object from entering the observation solid angle of the imaging device, so that only scattered light is imaged, or the reflected light and transmitted light are in an inclusion relationship with the observation solid angle, and the change in the propagation direction of the reflected light and transmitted light in the inspection object is observed as the brightness information of each point of the inspection object. Further, in the imaging device, the second filter means capable of selectively imaging the solid angle regions having different light attributes within the irradiation solid angle reflected by the solid angles of the reflected light and the transmitted light is provided, so that for each arbitrary solid angle region, the change occurring at the feature point of the inspection object can be captured, and the inspection light can be irradiated at an accurate irradiation solid angle corresponding to the minute light changes occurring at various inspection objects and various feature points to be detected.

[0025] The second filter means mentioned here may, for example, in the imaging device, selectively split the reflected light and transmitted light in the inspection object for each different light attribute and then image the amount of each light with an optical sensor, or may be provided with a filter that selectively transmits only light of different light attributes for each pixel of the optical sensor.

[0026] When irradiating the inspection target with inspection light having a substantially uniform irradiation solid angle according to the present invention, regarding the change in the solid angle of the reflected light or transmitted light that occurs when the reflection direction or transmission direction changes due to a defect or the like, even if it is very small, in order to be able to detect the change, with respect to the change in the solid angle, the change in the amount of light within the observation solid angle is maximized, and for other changes, it is minimized. By adjusting the relative relationship between the annular solid angle region formed concentrically within the irradiation solid angle of the inspection light and the observation solid angle of the imaging device with respect to its shape, angle, and size, it becomes possible to selectively capture only the change in the solid angle of the reflected light or transmitted light. Further, by setting arbitrary solid angle regions having different light attributes within the irradiation solid angle, it is possible to simultaneously observe the change in the amount of light for each of the solid angle regions, and it becomes possible to continuously supplement the change in light corresponding to the change in light at various characteristic points of the inspection target. Therefore, capturing such a slight change in light due to minute defects or the like was difficult with a conventional lighting device in which the shape, angle, and size of the irradiation solid angle of the inspection light differed for each point on the inspection target surface, but in the lighting device according to the present invention, it becomes possible to capture it.

[0027] In order to control the magnitude of the irradiation solid angle of the inspection light irradiated to each point of the inspection target to be substantially uniform and to be able to adjust the inclination distribution of the irradiation solid angle with respect to the optical axis center, the first light shielding mask, the first filter means, or the third filter means integrating the functions of both, or the relay image of the first light shielding mask, the first filter means, or the third filter means integrating the functions of both may be arranged at positions before and after centered on the focal position of the lens. Hereinafter, when described by representing the first light shielding mask, that is, by changing the opening of the first light shielding mask, the irradiation solid angle at each point of the inspection target can be set to a desired shape and magnitude. Further, if the first light shielding mask is arranged at the focal position of the lens, the optical axes of the irradiation solid angles of the inspection light all become parallel to the optical axis of the inspection light. If it is arranged on the lens side from the focal position of the lens, the irradiation solid angle of the inspection light can be inclined in the direction in which the inspection light spreads, and if it is arranged outside the focal position of the lens, the irradiation solid angle of the inspection light can be inclined in the direction in which the inspection light narrows. Thus, by the arrangement of the first light shielding mask and the change of its opening, various adjustments can be made for the irradiation solid angle of the inspection light that directly affects the solid angle of the reflected light, transmitted light, or scattered light from the inspection target, and the relative relationship between the inspection target and the observation solid angle of the imaging device that observes the reflected light, transmitted light, or scattered light from the inspection target can be made into a mode suitable for obtaining desired light and dark information. That is, in this way, even for an optical system in which the observation optical system used is not a telecentric optical system and the optical axis inclination of the observation solid angle changes at the outside of the field of view range and at the optical axis center, it is possible to set the irradiation solid angle and the observation solid angle for each point over the entire field of view to be in the regular reflection direction.

[0028] Furthermore, any of the solid angle regions having different light attributes set within the irradiation solid angle can be set as an arbitrary solid angle region within the irradiation solid angle uniformly set for the inspection object. Not only is the brightness of each point of the inspection object determined solely by the relative relationship between the irradiation solid angle and the observation solid angle, but even without separately re-setting the relative relationship regarding the shape, optical axis, etc. of the irradiation solid angle and the observation solid angle, it is possible to simultaneously observe, as a change in the relative relationship with respect to the observation solid angle, the even tinier changes in light for each of the solid angle regions at substantially the same conditions at all points within the visual field range of the inspection object.

[0029] In this way, in the inspection system comprising the illumination device for inspection according to the present invention and an imaging device that uses the illumination device for inspection and images the light reflected, transmitted, or scattered by the inspection object, it is possible to obtain the desired light and dark information for minute feature points because the light and dark at each point of the inspection object are determined by the amount of light traveling from each point of the inspection object to the imaging device, which is reflected light, transmitted light, or scattered light, and since the amount of light is determined by the inclusion relationship between the solid angle of the reflected light, transmitted light, or scattered light from each point of the inspection object and the observation solid angle of the imaging device. It has a function of adjusting the irradiation solid angle of the inspection light that directly affects the reflected light or transmitted light from each point of the inspection object to be substantially uniform, and furthermore, the inside of the irradiation solid angle is divided into arbitrary solid angle regions having different wavelength bands, polarization planes, or light amounts. Further, by forming a plurality of annular solid angle regions that are concentrically arranged within the irradiation solid angle and have no adjacent parts, even on a surface where the normal of the surface of the inspection object does not coincide with the observation optical axis, the imaging device can selectively observe the amount of light for each of the divided regions so that the change in the optical properties including the change in the propagation law of the object light returned from the inspection object is observed as the same uniform detection sensitivity as the detection sensitivity for a surface where the normal of the surface of the inspection object coincides with the observation optical axis.

[0030] In order for the light and dark information of the inspection object imaged by the imaging device to show a substantially uniform change over the entire imaging range, the inclusion relationship between the observation solid angle formed at each point of the inspection object by the imaging device and the solid angle of the reflected light, transmitted light, or scattered light from each point of the inspection object must be maintained substantially constant. This can be achieved by moving the first light-shielding mask, the first filter means, or even the relay image of the third filter means, or the first light-shielding mask and the first filter means, or even the relay image of the third filter means, to positions before and after centered on the focal position of the lens, so as to make the irradiation solid angle of the inspection light and the solid angle region formed within the irradiation solid angle have a substantially uniform shape and size, and adjusting its inclination angle to match the inclination of the observation solid angle at each point of the inspection object.

[0031] Also, in order to be able to arbitrarily generate the irradiation solid angle of the inspection light with respect to the inspection object and any of the solid angle regions formed within the irradiation solid angle while maintaining a substantially constant relative relationship with the observation solid angle for each point in the irradiation range, at least one of the first light-shielding mask, or the first filter means, or in addition to the third filter means, at least one of the second light-shielding mask or the fourth filter means, or at least one of the fifth filter means having at least any one of the functions of the second light-shielding mask or the fourth filter means should be provided and arranged in the vicinity of the position where the inspection object is imaged by the lens. By doing so, while maintaining the shape, size, and inclination of the irradiation solid angle of the inspection light and any of the solid angle regions formed within the irradiation solid angle substantially uniform, both the irradiation region of the inspection light with respect to the inspection object and the light attributes of the irradiation region, and the irradiation solid angle with respect to each point of the inspection object and the solid angle region having specific light attributes can be independently adjusted.

[0032] In order to easily inspect the three-dimensional shape and the like of the inspection object, in addition to the first light-shielding mask, the first filter means, or the third filter means, or its relay image, the second light-shielding mask and the fourth filter means having a predetermined mask pattern are used, and this pattern may be imaged on the inspection object. If it is such a thing, uniform light and dark information with uniform light and dark changes can be obtained by the imaging device in the substantially uniform irradiation solid angle and the solid angle region having a specific light attribute adjusted by the first light-shielding mask and the first filter means. If there is a problem with the shape of the inspection object, distortion occurs in the pattern obtained as light and dark information by the imaging device, so that a shape defect can be easily detected.

[0033] When the solid angle of the reflected light or transmitted light of each point of the inspection object and the observation solid angle formed by the imaging device at each point of the inspection object are made substantially coincident with respect to its shape, size, and inclination, even if there are minute feature points on the inspection object, a change occurs in the inclusion relationship between the solid angle of the reflected light or transmitted light and the observation solid angle, and a change in light and dark information for the minute feature points can be obtained. The change rate of the light and dark information due to this change in the inclusion relationship can be controlled by appropriately setting the solid angle of the reflected light or transmitted light and the size of the observation solid angle. However, as it is, only a certain amount of light and dark information depending on the sizes of the solid angles of both can be obtained. Therefore, when an arbitrary solid angle region having a different wavelength band, polarization plane, or light quantity is formed within the irradiation solid angle for each point of the inspection object, it is reflected as a solid angle region having a different wavelength band, polarization plane, or light quantity within the solid angle of the reflected light or the transmitted light of each point of the inspection object. If the change in the light and dark information for the feature points is made to change according to the inclusion relationship between the solid angle region reflected within the solid angle of the reflected light or the transmitted light and the observation solid angle, minute change amounts for each of the solid angle regions can be detected simultaneously.

[0034] As an example for achieving this, the observation axis and the observation solid angle of the imaging device are set in the specular reflection direction or the specular transmission direction with respect to the irradiation optical path of the irradiation solid angle formed by the inspection light on the inspection object. By substantially aligning the reflection / transmission optical path of the solid angle formed by the reflected light or transmitted light from each point of the inspection object with the observation optical path of the observation solid angle of the imaging device with respect to each point of the inspection object, i.e., the observation optical axis, it can be realized.

[0035] Also, as another example for achieving this, the inspection light from the surface light source is reflected, the direction of its irradiation optical path is changed and it is irradiated onto the inspection object. The reflected light from the inspection object is transmitted and the direction of the reflection optical path is not changed, and the imaging device can be used to image it as the observation optical path input to the observation optical system. Or, the inspection light is transmitted and its irradiation optical path direction is not changed and it is irradiated onto the inspection object. The reflected light from the inspection object is reflected and the direction of the reflection optical path is changed, and a beam splitter is provided to enable the imaging device to image it as the observation optical path input to the observation optical system. By appropriately adjusting the irradiation solid angle of the inspection light with respect to each point of the inspection object, the observation solid angle and the observation optical axis of the imaging device with respect to each point of the inspection object are made to substantially coincide with the optical axis of the solid angle of the reflected light emitted from each point, it can be realized. Note that this beam splitter should be installed between the inspection object and the first light-shielding mask, the first filter means, or the third filter means, or the relay optical system for forming its relay image, so as to function to separate the irradiation optical path and the observation optical path.

[0036] Furthermore, in the imaging device, by providing sixth filter means capable of selectively imaging the light in the solid angle region having different wavelength bands, polarization planes, or light amounts reflected within the solid angle of the reflected light or the transmitted light, the brightness changes generated by the inclusion relationship between each solid angle region and the observation solid angle can be detected simultaneously.

Advantages of the Invention

[0037] As described above, according to the inspection illumination device and the illumination optical system of the present invention, an annular solid angle region arranged concentrically within the irradiation solid angle of the inspection light irradiated to each point of the inspection target reflects the inclination near each point of the inspection target by means of bright and dark portions and the brightness of intermediate gradations, and while maintaining a constant sensitivity for detecting the inclination near each point of the inspection target, the size and shape of the solid angle regions having different wavelength bands, polarization planes, or light amounts formed within the irradiation solid angle can be freely adjusted. Therefore, the inclusion relationship between the solid angle of the reflected light, transmitted light, or scattered light from each point of the inspection target, and the solid angle regions having different wavelength bands, polarization planes, or light amounts reflected within the solid angle, and the observation solid angle formed at each point of the inspection target by the imaging device can be uniformly set, and even minute defects that were difficult to detect conventionally can be detected with the same detection sensitivity.

Brief Description of the Drawings

[0038]

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Embodiments for Carrying Out the Invention

[0039] The first embodiment of the present invention will be described with reference to FIG. 1. Note that the present invention is not limited to the content described in the following embodiments. In addition, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments may be combined as appropriate or selectively used as appropriate.

[0040] The inspection system 200 of the present invention irradiates the inspection target W with irradiation light by an irradiation optical path L1 by the inspection illumination device 100 and the illumination optical system 101, forms an irradiation solid angle IS at each point of the inspection target W, and the reflected / transmitted light L2 returned from the inspection target W is captured by the observation optical system K of the imaging device C, thereby capturing an image of the inspection target W and performing an inspection based on the image information. In FIG. 1, the observation optical system for capturing the transmitted light L2 of the inspection target W is denoted as K1, the imaging device is denoted as C1, the observation optical system for capturing the reflected light L2 of the inspection target W is denoted as K2, and the imaging device is denoted as C2. However, the imaging device for capturing the reflected light and the transmitted light may be either one of them or may be provided with both.

[0041] The inspection illumination device 100 and the illumination optical system 101 include a surface light source 1 that emits inspection light, a lens 2 provided between the surface light source 1 and the inspection target W, which forms an irradiation solid angle IS for the inspection target with the light radiated from the surface light source 1 as inspection light L1 irradiated onto the inspection target, and a first light shielding mask M1 provided before and after the focus position of the lens 2 with the focus position of the lens 2 as the center, which shields and forms the irradiation solid angle IS of the inspection light irradiated to each point of the inspection target. As shown in FIG. 10 described later, the first light shielding mask M1 is provided with a plurality of annular solid angle regions arranged concentrically within the irradiation solid angle IS and arranged concentrically so as not to have adjacent portions to each other. The inspection illumination device 100 and the illumination optical system 101 can form the same irradiation solid angle IS regardless of the distance from the inspection illumination device 100 and the illumination optical system 101 to the inspection target W and the position of each point of the inspection target W. The irradiation solid angle IS can be set to have the same relative angle with respect to the observation solid angle OS for each point of the inspection target W formed when the imaging device C images the reflected / transmitted light L2 from the inspection target W through the observation optical system K.

[0042] Further, the inspection illumination device 100 and the illumination optical system 101 may further include first filter means F1 adjacent to the first light shielding mask M1, which can divide the inspection light into arbitrary solid angle regions having partially different light attributes with light in different wavelength bands, different polarization planes, or different light amounts, or can be set so that the light attributes change continuously. Also, the first light shielding mask M1 and the first filter means F1 may be a third filter means F3 unified as means for forming a solid angle region and an irradiation solid angle, having at least one of their functions.

[0043] Also, between the first light-shielding mask M1 and the surface light source 1, and in the vicinity where the lens 2 forms an image with respect to the inspection target W, at least one of a second light-shielding mask M2 and a fourth filter means F4 that transmits only light having a specific attribute is further provided. By the second light-shielding mask M2 or the fourth filter means F4, the irradiation region and irradiation pattern of the inspection light with respect to the inspection target may be arbitrarily generated. Furthermore, the second light-shielding mask M2 and the fourth filter means F4 that transmits only light having a specific attribute may be a fifth filter means F5 having at least the functions of at least one of the second light-shielding mask M2 and the fourth filter means F4. In addition, in the description of FIG. 2 and FIGS. 3, 4, 5, 6, and 7, the description and illustration of the second light-shielding mask M2, the fourth filter means F4, and the fifth filter means F5 are omitted for the sake of simplicity. However, in any embodiment, the second light-shielding mask M2, the fourth filter means F4, and the fifth filter means F5 may be installed in the same manner as in FIG. 1.

[0044] Next, a second embodiment of the present invention will be described with reference to FIG. 2. The first light-shielding mask M1, the first filter means F1, and the third filter means F3 described in FIG. 1 may be arranged between the surface light source 1 and a relay optical system 106 (for example, lenses arranged in tandem), and a relay image RI formed by the relay optical system 106 may be used instead of the first light-shielding mask M1, the first filter means F1, and the third filter means F3. The relay image RI is a reduced image of the first light-shielding mask M1, the first filter means F1, and the third filter means F3. Note that the positions of the first light-shielding mask M1, the first filter means F1, and the third filter means F3 may also be changed along the illumination optical path L1 (that is, a configuration in which the relay image RI of the first light-shielding mask M1, the first filter means F1, and the third filter means F3 can be arranged near the focal position of the lens 2).

[0045] The inspection light irradiated onto each point of the inspection target W by the inspection illumination device 100 and the illumination optical system 101 has a constant shape regardless of the position on the inspection target W and the distance from the inspection illumination device 100 and the illumination optical system 101. By adjusting along the irradiation optical path L1 near the focal position of the lens 2 the first light-shielding mask M1, the first filter means F1, and the third filter means F3 that form the irradiation solid angle IS, or the relay image RI imaged by the relay optical system 106, the inclination of each irradiation solid angle IS with respect to the inspection target W can be made constant, or the inclination can be adjusted around the irradiation optical axis. Further, the irradiation solid angle formed in this way is formed by the shaped transmitted light radiated at an equal angle from the lens 2 by the lens 2, the first light-shielding mask M1 arranged near its focal position, the first filter means F1, and the third filter means F3, or the relay image RI imaged by the relay optical system 106, and is not necessarily formed by the imaging light that images the surface light source 1 on the inspection target W by the lens 2.

[0046] When the shape and size of the irradiation light IS are such that the object light returned from the inspection target W is direct light such as regular reflected light or regular transmitted light, it is maintained as the solid angle of the object light. The solid angle DS of this direct light has the same shape as the irradiation solid angle IS, and only the light energy contained within the solid angle DS of the direct light is supplemented within the observation solid angle OS formed at each point of the inspection target by the imaging device and imaged as the brightness of each point. Therefore, by keeping the solid angle elements, which are the relative relationships of these solid angles, uniform, changes in the optical physical properties of the inspection target are quantitatively reflected in the imaging image. The mechanism will be described later.

[0047] FIG. 3 shows the first embodiment described in FIG. 1, which reflects the inspection light emitted from the surface light source 1, changes the direction of its irradiation optical path L1, irradiates the inspection object W1, transmits the reflected light to be observed from the inspection object W1, and changes the direction of the reflection optical path L2 without changing it, so that it can be imaged by the imaging device as the observation optical path L3 input to the observation optical system K. Alternatively, the inspection light is transmitted without changing the direction of its irradiation optical path L1 and irradiates the inspection object W2, and the reflected light to be observed from the inspection object W2 is reflected to change the direction of the reflection optical path L2, so that it can be imaged by the imaging device as the observation optical path L3 input to the observation optical system K. A beam splitter 4 is provided, and the irradiation solid angle of the inspection light with respect to each point of the inspection object is appropriately adjusted so that the observation solid angle of the inspection object of the imaging device and the optical axes of the solid angles of the reflected light or the transmitted light emitted from each point thereof can be substantially aligned. This is the third embodiment of the present invention.

[0048] The beam splitter 4 described with reference to FIG. 3 should be installed between the inspection object W and the irradiation optical path L1 and the reflection optical path L2 to be observed, that is, the irradiation optical axis and the observation optical axis are made to coincide and coaxial, and the first light shielding mask M1 and the first filter means F1, or the third filter means F3, or the relay optical system 106 for forming its relay image RI, so as to function to separate the irradiation optical path L1 and the observation optical path L3. Adding the relay optical system 106 to the third embodiment is the fourth embodiment shown in FIG. 4. In the third embodiment, the beam splitter 4 is arranged between the lens 2 and the first light shielding mask M1 and the first filter means F1, or the third filter means F3, which is the fifth embodiment of the present invention shown in FIG. 5. In this fifth embodiment, adding the relay optical system 106 is the sixth and seventh embodiments of the present invention shown in FIGS. 6 and 7. The sixth embodiment is the case where the relay image RI is located on the side opposite to the inspection object of the beam splitter 4. The seventh embodiment is the case where the relay image RI is located on the inspection object side of the beam splitter 4, and both are effectively operative as embodiments of the present invention.

[0049] In the fifth, sixth, and seventh embodiments, the lens 2 or 3 is also used for the imaging device to capture the reflected light of the inspection target W according to its observation solid angle. Therefore, it is used to form the observation solid angle while forming the irradiation solid angle. When the lens 3 is included in the imaging device as part of the observation optical system, the irradiation optical system includes the part from the surface light source 1 to the beam splitter 4. Conversely, when the inspection illumination device includes the lens 2, the imaging device including the observation optical system also extends to the beam splitter.

[0050] Also, in the fifth, sixth, and seventh embodiments, since the lens 2 or the lens 3 is shared by the irradiation optical system and the observation optical system, on the observation optical system side, there is a problem that a part of the irradiation light irradiated from the irradiation optical system is reflected to the observation optical system side by the lens 2 or the lens 3. In a normal coaxial optical system, since uniform irradiation light is irradiated over the entire aperture, this reflection from the lens is relatively dim compared to the reflected light from the inspection target, and can be ignored if the reflection from the lens is uniform. However, in the present invention, the irradiation light including the pattern for forming the irradiation solid angle is irradiated by the first light shielding mask M1 and the first filter means F1, or the third filter means F3, or the relay optical system 106. Since this pattern can also be seen in the reflected stray light reflected from the lens 2 or the lens 3, it is necessary to shield only the reflected stray light from this lens.

[0051] Therefore, in the fifth, sixth, and seventh embodiments, for the reflected stray light generated by the reflection of the irradiation light by the lens, a first polarizing filter PL1 is installed on the non-inspection object side of the beam splitter 4 on the irradiation optical path L1, and a second polarizing filter PL2 is installed on the non-inspection object side of the beam splitter 4 on the observation optical path L3. In addition, a quarter-wave plate WS1 or WS2 is installed on the inspection object side of the lens 2 or the lens 3. The first polarizing filter PL1 and the second polarizing filter PL2 are set as cross-nicolars with their transmission axes orthogonal to each other to cut the reflected stray light from the lens. When the transmission axis of the quarter-wave plate WS1 or WS2 is inclined by 45 degrees with respect to the transmission axis of the first polarizing filter PL1, the irradiation light irradiated on the inspection object W becomes circularly polarized light. The reflected light from the inspection object that preserves and returns this polarization becomes linearly polarized light inclined by 90 degrees with respect to the transmission axis of the first polarizing filter PL1 after passing through the quarter-wave plate WS1 or WS2 again, and can pass through the second polarizing filter PL2 installed on the observation optical path. As a result, only the reflected stray light from the lens, which is linearly polarized light in the direction of the transmission axis of the first polarizing filter PL1, is cut, and the reflected light from the inspection object can be observed. Also, when the object light returned from the inspection object W is scattered light, even if the irradiation light is polarized light, it becomes non-polarized light, so it can still pass through the second polarizing filter PL2 installed on the observation optical path. Further, when the transmission axis of the quarter-wave plate WS1 or WS2 is installed in the same direction as the transmission axis of the first polarizing filter PL1 or inclined by 90 degrees, the irradiation light that has become linearly polarized light by the first polarizing filter PL1 is directly irradiated on the inspection object W. In this case, the reflected light from the inspection object W also remains the same linearly polarized light, so it is blocked by the second polarizing filter installed on the observation optical path, but the non-polarized scattered light component passes through. In this case, only the scattered light from the inspection object can be observed. Note that when only scattered light is to be observed, the quarter-wave plate may not be installed. Also, the first polarizing filter PL1, the second polarizing filter PL2, and the quarter-wave plate WS1 or WS2 are only shown in FIG. 5 and are omitted in FIGS. 6 and 7 for simplicity, but they may be installed in the same manner as in FIG. 5.

[0052] Here, the object light consists of direct light that preserves polarization at a certain ratio and non-polarized scattered light components. When observed through an analyzer that irradiates polarized light and transmits this polarization, compared to the component ratios of direct light and scattered light when irradiated with non-polarized light, the component ratios of the direct light that preserves and returns polarization and the scattered light that returns as non-polarized light increase according to the law of conservation of energy. In the bright field for observing direct light, the scattered light component often becomes noise, and reducing this component leads to an improvement in the S / N (signal-to-noise ratio) in converting changes in the optical properties of the inspection target W into light brightness information. Although the observed brightness itself is reduced by a polarization filter or the like, the fact that changes in the optical properties of the inspection target W can be detected with a higher S / N is more advantageous as the changes are smaller.

[0053] The irradiation solid angle IS, and the relative relationship between the solid angle DS of direct light such as specular reflection light and direct transmission light returned from the object directly reflecting this irradiation solid angle IS and the observation solid angle OS is referred to as the solid angle element. In the bright field for imaging the brightness of direct light, the brightness profile of the image changes due to this solid angle element. The brightness with respect to the inclination of the inspection target in the bright field depends on the plane half-angle θi of the irradiation solid angle IS and the plane half-angle θo of the observation solid angle OS. The maximum detectable inclination angle of the inspection target W is 1 / 2 of θi + θo. If, for example, an imaging device C that outputs an 8-bit brightness gradation is used during this inclination angle, 1 / 256 of 1 / 2 of θi + θo becomes the theoretical detection sensitivity with respect to the inclination of the inspection target W. For example, when θi and θo are each 1 degree, a 1x lens is used, and a photosensor with a square pixel of 3.45 μm per pixel is used, and visible light is irradiated under the imaging conditions of a normal camera with the inspection lighting according to the present invention, the theoretical detection resolution of the inclination of the inspection target W is 0.0039 degrees, and the theoretical resolution in the depth direction is 0.24 nm. This is an absurd value that already exceeds the Rayleigh diffraction limit. The horizontal resolution is at most 3.45 μm of the pixel size, and with observation using visible light of a normal camera, without using a microscope and with normal imaging, it has a resolution more than 1000 times that of a general microscope, indicating that this is already at the electron microscope level of resolution.

[0054] Therefore, when observing the inspection target W according to the present invention, since brightness accuracy about 1 / 1000 of normal observation is required, it is necessary to suppress stray light in the observation optical system as much as possible, and a mechanism for cutting stray light by combining the cross Nicol of the polarizing filter and a quarter-wave plate becomes essential.

[0055] Next, the relationship between the irradiation solid angle IS and the solid angle RS of the reflected light which is the solid angle DS of the object light returned from the inspection target W with the same solid angle as the irradiation solid angle will be described below with reference to FIGS. 8 and 9.

[0056] In the present invention, the first light shielding mask and the first filter means, or the third filter means form a plurality of annular solid angle regions arranged concentrically so as not to have adjacent portions, and moreover, the light attribute thereof can be arbitrarily changed, and at all positions in the entire visual field range of the inspection target W imaged by the imaging device C, irradiation light can be irradiated under the same conditions, and moreover, the irradiation optical axis and the irradiation solid angle can be set to a state suitable for the optical characteristics of the imaging device. FIG. 8(a) shows the respective irradiation solid angles IS and IS′ at different positions P and P′ of the inspection target W when the inspection target W is irradiated with a surface light source 1 which is a general conventional illumination, and it can be seen that the shape and the optical axis of the irradiation solid angle are different between the two. Further, FIG. 8(b) shows the state of the irradiation light according to the present invention, and the irradiation solid angle can be formed under the same conditions not only at different positions P and P′ of the inspection target W but also at all positions in the entire visual field range of the inspection target W. By doing so, particularly in the bright field illumination method for observing the direct light of the reflected light and the transmitted light returned from the inspection target W, a remarkable effect can be expected. Here, the reflected light refers to regular reflected light returned from a mirror surface or the like, and the transmitted light refers to regular transmitted light transmitted through a transparent object. Also, in the dark field illumination method for observing scattered light, many of them change depending on the light attribute and the irradiation solid angle irradiated with the scattered light, and it becomes possible to detect changes in the optical physical properties of a minute inspection target W which could not be realized by conventional illumination.

[0057] Fig. 9(a) focuses on point P on the inspection target W and considers the case where inspection light with an irradiation solid angle IS is irradiated on point P. When the plane including point P of the inspection target is partially inclined by φ, the imaging device C shows how the brightness of point P changes with respect to the observation solid angle OS formed by the imaging device C at point P, and how the relative relationship of each solid angle is when the solid angle RS1 of the reflected light from point P changes like the solid angle RS2.

[0058] In Fig. 9(a), the shapes and sizes of the solid angles RS1 and RS2 of the reflected light from point P are equal to the irradiation solid angle IS of the inspection light with respect to point P. Also, the inclination of the solid angle RS1 of the reflected light is inclined by the same amount as the inclination θ of the irradiation solid angle IS of the inspection light in a direction that is line-symmetric to the irradiation solid angle IS of the inspection light with respect to the normal line erected at point P. At this time, assuming that the observation solid angle OS formed by the imaging device C with respect to point P coincides with the solid angle RS1 of the reflected light and its size is extremely small compared to the solid angle RS1 of the reflected light, the brightness of point P captured by the imaging device C is limited by the size of the observation solid angle OS, and does not change even if the solid angle RS1 of the reflected light is inclined within the range where this inclusion relationship does not change. However, it is assumed that the light energy within the irradiation solid angle IS, and the solid angles RS1 and RS2 of the reflected light is uniformly distributed within those solid angles.

[0059] Next, consider the case where the plane containing the point P of the inspection target W is partially inclined by φ in FIGS. 9(a) and 9(b). The solid angle RS1 of the reflected light from the point P will be inclined by 2φ as shown by the dotted line RS2 in the figure. At this time, if there is no inclusion relationship between the solid angle RS2 of the reflected light from the point P and the observation solid angle OS formed by the imaging device C with respect to the point P, the brightness of the point P as seen from the imaging device C will be 0. However, if there is a partial inclusion relationship between the observation solid angle OS formed by the imaging device C with respect to the point P, the light included in the solid angle portion where the two overlap will be reflected as the brightness of the point P. That is, when the plane half-angle θi of the solid angle RS2 of the reflected light from the point P is larger than the angle obtained by subtracting the plane half-angle θo of the observation solid angle OS from the inclination angle 2φ of the reflected light, and is smaller than the angle obtained by adding the plane half-angle θo of the observation solid angle OS to the inclination angle 2φ of the reflected light, the brightness of the point P changes depending on the inclination angle 2φ of the reflected light. However, if the plane half-angle θi of the irradiation solid angle IS is larger than the angle obtained by adding the plane half-angle θo of the observation solid angle OS to the inclination angle 2φ of the reflected light generated by the partial inclination of the inspection target W, the brightness of the point P does not change. Also, if the plane half-angle θo of the observation solid angle OS is larger than the sum of the inclination angle 2φ of the reflected light and the plane half-angle θi of the solid angle RS of the reflected light, the brightness of the point P also does not change. Ultimately, this shows that the brightness of the point P is determined by the inclusion relationship between the solid angle RS of the reflected light from the point P and the observation solid angle OS with respect to the point P, and by setting the relative relationship regarding the shape, size, and inclination between the irradiation solid angle IS of the inspection light irradiated to the point P and the observation solid angle OS with respect to the point P, the change in the brightness of the point P can be controlled.

[0060] Here, the larger the sum θi + θo of the plane half-angles of the irradiation solid angle IS and the observation solid angle OS, or the larger the absolute value |θi - θo| of the difference between the plane half-angles of the irradiation solid angle IS and the observation solid angle OS, the smaller the sensitivity to changes in the inclination of the inspection target W, that is, the amount of change when supplementing the inclination angle as a change in the brightness of point P. That is, in order to detect a minute inclination of the inspection target W with high sensitivity, the smaller the sum of the plane half-angles θi + θo of the irradiation solid angle IS and the observation solid angle OS, or the smaller the absolute value |θi - θo| of the difference between the plane half-angles of the irradiation solid angle IS and the observation solid angle OS, the better. However, if this is done, in the portion where the inclination of the inspection target W becomes larger than 1 / 2 of the sum θi + θo of the plane half-angles of the irradiation solid angle IS and the observation solid angle OS, the object light returned from the inspection target W cannot be supplemented. Even if the sensitivity to the inclination of the inspection target W increases, the detection visual field range for the inspection target W becomes narrower.

[0061] Figure 9(b) is a cross-sectional view in a plane including the irradiation optical axis of the inspection light, the normal line of point P, and the reflected light axis from point P in (a), and the inclination of each element and its inclusion relationship can be grasped more quantitatively. However, in Figure 9(b), the case where the observation solid angle OS is larger than the irradiation solid angle IS, that is, the solid angle RS1 of the reflected light, is illustrated. When the inspection target W is inclined and the solid angle RS1 of the reflected light from point P becomes RS2 shown by the dotted line, in this figure, the inclusion relationship with the observation solid angle OS is lost, and the light energy within the observation solid angle OS becomes zero. Therefore, even if the light included in this observation solid angle OS is collected again at a point and imaged, point P can only be seen as completely dark. However, also in this case, by adjusting the relative relationship between the irradiation solid angle IS and the observation solid angle OS, an inclusion relationship between the solid angle RS of the reflected light and the observation solid angle OS is generated, and the brightness of point P changes according to the change in the size of the overlapping portion.

[0062] In Fig. 9(b), here, if the shape and size of the observation solid angle OS are the same as those of the irradiation solid angle IS and coincide with the inclination of the solid angle RS of the reflected light from point P, then if the inspection target W tilts even slightly from that state, at least the overlapping portion of the observation solid angle OS and the solid angle RS of the reflected light decreases, so the brightness of point P seen through the observation solid angle OS changes accordingly. Moreover, the smaller each solid angle is, the greater the change in the brightness of point P when the inspection target W tilts by the same angle, and conversely, the larger each solid angle is, the smaller the change in the brightness of point P when the inspection target W tilts by the same angle. Also, if the shape, size, inclination, etc. of the irradiation solid angle IS and the observation solid angle OS are appropriately set corresponding to the change in light generated at the desired feature points of the inspection target, it becomes possible to accurately detect the feature points that could not be stably detected until now. In the present invention, paying attention to this principle, as will be described later, the shape of the irradiation solid angle is made to include a plurality of concentric circular annular solid angle regions arranged so as not to have adjacent portions to each other, and the inclusion relationship between this annular solid angle region and the observation solid angle OS is kept the same even in the portion where the inclination of the inspection target W is relatively large, so that the sensitivity to the inclination can be maintained.

[0063] Next, with reference to Fig. 10, an embodiment of the first light-shielding mask M1, the first filter means F1, and the third filter means F3 will be described.

[0064] As shown in FIG. 10(a), for example, the first light-shielding mask M1 has light-shielding portions M11, M12, and M13 that substantially block light, forming non-adjacent annular openings T1, T2, and T3. In FIG. 10(a), the periphery is shown as the light-shielding portion M13 and the central portion as the opening, but conversely, the central portion may be the light-shielding portion. Also, the light-shielding portion may be a portion that blocks only light having a specific attribute. Further, as shown in FIG. 10(b), in the first filter means F1, patterns F11, F12, and F13 for forming solid angle regions with three different light attributes are set. Here, it is a radial pattern centered on the optical axis, but this may also be optimized to an arbitrary pattern depending on the feature point of interest of the inspection target. The third filter means F3 shown in FIG. 10(c) is an integration of the first light-shielding mask M1 and the first filter means F1. The non-adjacent annular solid angle regions T1, T2, and T3 shown in (a) are each divided into three portions F11, F12, and F13 with different light attributes. In this way, it becomes possible to determine in which direction the inspection target is tilted. Note that the three portions F11, F12, and F13 with different light attributes may have their light attributes changing continuously, or the light attributes may change for each annular transmission portion.

[0065] FIG. 11 shows the relationship between the reflected lights RS1 and RS2 and the observation solid angle OS formed at point P on the inspection target W when an irradiation solid angle having a plurality of concentric circular annular solid angle regions arranged so as not to have adjacent portions is formed at point P on the inspection target W. Case (a) shows the situation where the irradiation solid angle IS and the observation solid angle OS with respect to the inspection target W are in the specular reflection direction with respect to each other. The observation solid angle OS has an inclusion relationship with the bright portion at the center of the irradiation solid angle, and point P is observed brightly. However, in FIG. 11(b), when the inspection target W is tilted by φ, the solid angle RS2 of the reflected light that reflects while maintaining the solid angle IS of the irradiation light is tilted by 2φ with respect to the solid angle RS1 of the reflected light that was reflected in the specular reflection direction in (a). As a result, it also tilts by 2φ with respect to the optical axis of the observation solid angle OS. In the example shown in (b), the inclusion portion of the observation solid angle OS lies between the annular solid angle regions formed concentrically within the solid angle RS2 of the reflected light, and the brightness of point P becomes darker accordingly.

[0066] FIG. 12 shows the relationship between the solid angle RS of the reflected light returned from the inspection target W and the observation solid angle OS when the optical axis of the irradiation solid angle and the optical axis of the observation solid angle OS formed at point P by the imaging device C are made coaxial when an irradiation solid angle having a plurality of concentric circular annular solid angle regions arranged so as not to have adjacent portions is formed at point P on the inspection target W using the beam splitter. It shows how the brightness of point P changes with respect to the tilt of the inspection target W. In FIG. 12, the plane half-angle θi of the bright portion solid angle region at the center of the irradiation solid angle is set equal to the plane half-angle θo of the observation solid angle OS, and the width of the bright annular solid angle region arranged concentrically within the irradiation solid angle and the dark annular solid angle region between adjacent bright annular solid angle regions is set to twice the plane half-angle θo of the observation solid angle OS, that is, 2θo.

[0067] (a) of Fig. 12 shows a state where the normal of the surface near the point P to be inspected coincides with the irradiation optical axis and the observation optical axis. At this time, the brightness of point P is at its maximum value. When the inspection target W is tilted, the brightness of point P gradually darkens as shown in (b). When the tilt of the inspection target W reaches θo, as shown in (c), the observation solid angle OS overlaps with the dark annular solid angle region within the solid angle of the reflected light RS that holds and reflects the irradiation solid angle IS, and the brightness of point P reaches its minimum value. Further, as the inspection target W continues to tilt and its tilt reaches 2θo through (d), as shown in (e), the observation solid angle OS overlaps with the bright annular solid angle region within the solid angle of the reflected light RS that holds and reflects the irradiation solid angle IS, and the brightness of point P returns to its maximum value again. During this period, the change in the brightness of point P with respect to the tilt of the inspection target W is approximately linear, and it alternately repeats from the maximum value to the minimum value and from the minimum value to the maximum value every time the tilt of the inspection target W is an integer multiple of θo. After its tilt exceeds 1 / 2 of the sum θi + θo of the plane half-angle θi of the irradiation solid angle and the plane half-angle θo of the observation solid angle, the inclusion relationship between the irradiation solid angle IS and the observation solid angle OS disappears, so the brightness of point P remains at its minimum value.

[0068] The following will explain each element in detail.

[0069] The surface light source 1 may be one in which one or more chip-type LEDs are arranged, an organic EL, one in which a light guide plate is guided from a side light, or the like. Note that the position of the surface light source 1 may be changeable along the illumination optical axis L1, and through the first light shielding mask M1 and the first filter means F1, and the third filter means F3 disposed near the focal position of the lens 2 and before and after it, the lens 2 can form a uniform irradiation solid angle IS regardless of the distance from the inspection target W. However, the light forming this irradiation solid angle IS is composed of light emitted from each point of the surface light source, and which point the light is emitted from is determined by how far away from the lens 2 on the irradiation optical axis L1 and the distance, and how far away in which direction orthogonal to the irradiation optical axis from the irradiation optical axis and the distance and direction. Although it also changes depending on the distance between the surface light source 1 and the lens 2, for all irradiation solid angles IS, the light beam forming one irradiation solid angle is not necessarily light emitted from one point of the surface light source. If the light beam forming a certain irradiation solid angle is formed by the light beam emitted from one point of the surface light source 1, the position where the irradiation solid angle is formed is the position where the surface light source 1 is imaged by the lens 2. The irradiation solid angle used in the present invention is not only at the imaging position, but also if the surface light source includes light beams emitted from a plurality of points other than that, it can form a more uniform irradiation solid angle without reflecting the luminance unevenness of the surface light source.

[0070] Also, by configuring the portion on the irradiation optical path L1 from the surface light source 1 to the first light shielding mask M1 and the first filter means F1, or the third filter means F3 with a flat panel display such as a liquid crystal monitor device that combines a color liquid crystal or the like capable of dynamically changing the emission wavelength distribution, luminance distribution, and polarization state distribution of the irradiation surface and a white light source, it is possible to further correspond to various types of inspection targets. By doing so, it becomes possible to control the display in real time and form various irradiation solid angles, and it becomes possible to construct a lighting for inspection, an illumination optical system, and thus an inspection system with a higher degree of optimization freedom.

[0071] The relay optical system 116 is, for example, a refractive lens system that passes illumination light passing through the first light-shielding mask M1 and the first filter means F1, or the third filter means F3. It may be a single lens or may be composed of a plurality of lenses. In addition, as the lens, in addition to those with an uneven shape, a refractive index distribution type lens and the like are also included.

[0072] With respect to the lens 2, the first light-shielding mask M1 and the first filter means F1, or the third filter means F3 for forming an irradiation solid angle are optical elements that determine the numerical aperture of the irradiation optical system. Since the lens 2 is a substantially telecentric optical system on the inspection target W side, it is arranged near the focal position on the side opposite to the inspection target of the lens 2. However, in the case of the fifth, sixth, and seventh embodiments, in order to also function as the objective lens of the observation optical system, an aperture stop for forming an observation solid angle is installed near the focal position on the side opposite to the inspection target of the same lens 2 as the irradiation system. Therefore, if this focal position is on the side opposite to the inspection target of the beam splitter 4 that separates the irradiation optical path and the observation optical path, apart from the first light-shielding mask M1 and the first filter means F1, or the third filter means F3 for forming the irradiation solid angle that determines the numerical aperture of the irradiation system, i.e., the size, shape, pattern, etc. of the irradiation solid angle, an aperture stop can be installed. However, if the focal position of the lens 2 is on the inspection target side of the beam splitter, by using the relay optical system, an relay image for forming the irradiation solid angle is formed at the same position as the aperture stop that determines the size and shape of the observation solid angle, and within that range, it is possible to freely form the irradiation solid angle.

[0073] The irradiation solid angle IS formed by the first light-shielding mask M1 has the same planar half-angle of the solid angle region that is the central opening as the planar half-angle θo of the observation solid angle OS. For the inclination of the inspection target W, the reflected light RS having the same solid angle as the irradiation solid angle is inclined, and the inclusion portion between the observation solid angle OS and the central solid angle region of the reflected light RS always changes. Therefore, this is the condition with the highest detection sensitivity for inclination. Further, the smaller the planar half-angle θo of the observation solid angle, the higher the detection sensitivity. To maximize the brightness change of the observed luminance with respect to the inclination of the inspection target W, a solid angle region in the form of an annular light-shielding portion is provided concentrically outside the central opening. If the width of the light-shielding portion is set to twice the planar half-angle θo of the observation solid angle OS, when the inclination of the inspection target W reaches θo, regardless of the direction of the inclination, the observation solid angle OS completely enters the solid angle region that becomes the light-shielding portion, and the light energy captured by the observation solid angle becomes minimum, resulting in the maximum brightness change. Further, a solid angle region in the form of an annular opening is provided concentrically outside the light-shielding portion. If the width of the opening is set to twice the planar half-angle θo of the observation solid angle OS, when the inspection target W is inclined by θo further, the observation solid angle OS completely enters the solid angle region that becomes the opening, and the light energy captured by the observation solid angle becomes maximum, resulting in the maximum brightness change and the same brightness as when the observation solid angle OS coincides with the optical axis center of the solid angle RS of the reflected light. Thereafter, if the annular solid angle regions of the light-shielding portion and the opening are arranged concentrically with the same width, the brightness change is repeated with the same sensitivity with respect to the inclination of the inspection target W until the inclination of the inspection target W exceeds 1 / 2 of the sum θi + θo of the planar half-angle θi of the irradiation solid angle and the planar half-angle θo of the observation solid angle. When the inclination of the inspection target W exceeds 1 / 2 of the sum θi + θo of the planar half-angle θi of the irradiation solid angle and the planar half-angle θo of the observation solid angle, thereafter, even if the inspection target is inclined further, the observation solid angle OS cannot capture the light energy from the solid angle RS of the reflected light from the inspection target W, so the brightness becomes the lowest.Therefore, the widths of the dark portions, which are the light-shielding portions of the first light-shielding mask M1, and the bright portions, which are the non-light-shielded opening portions, are set to be twice the plane half-angle θo of the observation solid angle OS, and are formed as concentric circularly arranged annular openings and annular light-shielding portions at equal intervals. If the central portion is an opening having the same plane half-angle as the plane half-angle θo of the observation solid angle OS, then for the observation solid angle OS, the detection sensitivity for the inclination of the inspection target W can be set to be uniform and the most sensitive.

[0074] In the first light-shielding mask M1, the central portion may be a light-shielding portion having the same plane half-angle as the plane half-angle θo of the observation solid angle OS, the outer side thereof may be a concentric circularly arranged annular opening having a width of 2θo, and further the outer side thereof may be a concentric circularly arranged annular light-shielding portion having a width of 2θo. Subsequently, they may be alternately arranged up to the plane half-angle θi of the irradiation solid angle IS in the same manner. Furthermore, if the intervals between the light-shielding portions and the openings are made the same and their widths are changed, the region where the brightness changes due to the inclination can be changed, or the minimum brightness can be changed to a certain brightness. Furthermore, the degree of change in brightness due to the inclination of the inspection target W can also be changed. Moreover, the intervals between the light-shielding portions and the openings may be changed, and the inclusion relationship with the observation solid angle OS may be arbitrarily set within an arbitrary angular range as appropriate.

Explanation of Reference Numerals

[0075] 200: Inspection system 100: Illumination device for inspection C: Imaging device C1: Imaging device (used under different conditions in the same figure) C2: Imaging device (used under different conditions in the same figure) K: Observation optical system K1: Observation optical system (used under different conditions in the same figure) K2: Observation optical system (used under different conditions in the same figure) 1: Surface light source 11: Light-emitting surface 2: Lens 3: Lens (used under different conditions in the same figure) 4: Beam splitter L1: Irradiation optical path (irradiation optical axis) L2: Reflection / transmission / observation optical path (object optical path) L3: Observation optical path (observation optical axis) M1: First light-shielding mask M11: Light-shielding portion of the first light-shielding mask M12: Light-shielding portion of the first light-shielding mask M13: Light-shielding portion of the first light-shielding mask F1: First filter means F11: Portion that transmits light having a certain light attribute 1 of the first filter means F12: Portion that transmits light having a certain light attribute 2 of the first filter means F13: Portion that transmits light having a certain light attribute 3 of the first filter means F2: Second filter means (in the imaging device) F3: Third filter means M2: Second light-shielding mask F4: Fourth filter means F4: Fifth filter means 106: Relay optical system RI: Relay image R1: Relay image (used under different conditions in the same figure) R2: Relay image (used under different conditions in the same figure) W: Inspection object W1: Inspection object (used under different conditions in the same figure) W2: Inspection object (used under different conditions in the same figure) P: Certain point on the inspection object W P′: Another point on the inspection object W φ: Tilt angle of the inspection object IS: Irradiation solid angle IS′: Another irradiation solid angle θi: Planar half-angle of the irradiation solid angle OS: Observation solid angle θo: Planar half-angle of the observation solid angle RS: Solid angle of the reflected light RS1: Solid angle of the reflected light (used under different conditions in the same figure) RS2: Solid angle of the reflected light (used under different conditions in the same figure)

Claims

1. An inspection illumination device for irradiating an inspection object with inspection light and observing object light returned from the inspection object, comprising: a surface light source that emits the inspection light; a lens provided between the surface light source and the inspection object for forming an irradiation solid angle with respect to each point of the inspection object in the inspection light irradiated from the surface light source to the inspection object; and a first light-shielding mask arranged concentrically within the irradiation solid angle and forming a plurality of annular solid angle regions that do not have adjacent portions to each other, or a relay image of the first light-shielding mask, which is arranged between the surface light source and the lens, and can form the same irradiation solid angle simultaneously for each point of the inspection object regardless of the distance from the lens and the position of each point of the inspection object.

2. In Claim 1, a first filter means, or a third filter means integrating the functions of the first light-shielding mask and the first filter means, or a relay image of the first light-shielding mask and the first filter means, or a relay image of the third filter means, which is arranged between the surface light source and the lens and can further form a solid angle region having a specific light attribute within the irradiation solid angle.

3. In Claim 1 or 2, at least one of a second light-shielding mask and a fourth filter means, or a fifth filter means integrating the functions of the second light-shielding mask and the fourth filter means is further provided between the surface light source and the lens, and the irradiation region, irradiation shape, irradiation pattern, or light attribute of the inspection light with respect to the inspection object can be arbitrarily set.

4. In any one of Claims 1 to 3, in order to observe the object light returned from the inspection object, the irradiation solid angle can be set to have the same relative angle with respect to the observation solid angle formed at each point of the inspection object.

5. In any one of Claims 1 to 4, on the inspection object side of the lens, for the inspection object, the irradiation optical path and the reflection optical path of the reflected light returned from the inspection object and serving as the observation object are coaxial, and for the lens, a beam splitter that separates the irradiation optical path and the reflection optical path serving as the observation object is provided.

6. In any one of Claims 1 to 4, An inspection illumination device provided on the side of the lens to be re-inspected, which is coaxial with the irradiation optical path and the reflection optical path of the reflected light that is returned from the inspection target and becomes the observation target with respect to the inspection target, and includes a beam splitter that separates the irradiation optical path and the reflection optical path that becomes the observation target with respect to the first light shielding mask.

7. In claim 6, A first polarizing filter is installed on the irradiation optical path side input to the beam splitter, a second polarizing filter is installed on the reflection optical path side output from the beam splitter, and the inspection illumination device is set so that the transmission easy axes of the first polarizing filter and the second polarizing filter are perpendicular.

8. In claim 7, an inspection illumination device further including a quarter-wave plate on the inspection target side of the lens.

9. An inspection illumination device according to any one of claims 1 to 8, An imaging device that images light reflected, transmitted, or scattered in the inspection target, or an illumination optical system that irradiates the inspection target with inspection light incorporated in the observation optical system thereof.

10. Using the inspection illumination device according to any one of claims 1 to 8, An inspection system including an imaging device that images light reflected, transmitted, or scattered in the inspection target, wherein in the inspection light irradiated on the inspection target by the inspection illumination device, based on the shape, size, or inclination of the observation solid angle at each point of the inspection target of the imaging device, the shape, size, or inclination of the irradiation solid angle at each point of the inspection target is set, or the shape, size, or inclination of the irradiation solid angle and the observation solid angle are set to be substantially the same relatively.

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