JPH09210656A - Inspection device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To perform a defect inspection of a pattern having a pattern drawn on a circular surface to be inspected at high speed and with stable detection accuracy, and to perform a defect inspection process at a low cost. To get In an inspection device for inspecting a defect on a circular inspection surface provided with a predetermined pattern, an imaging optical system for forming an image of the pattern on the inspection surface and a light from the inspection surface are provided. Light detecting means for one-dimensionally detecting, rotating means for relatively rotating the image of the surface to be inspected and the light detecting means within the image plane, and the image of the surface to be inspected relative to the light detecting means. By comparing the image obtained by the image acquisition unit that forms an image of the surface to be inspected based on the signal obtained from the light detection unit when rotated, with the image information stored in advance, An inspection apparatus having defect detection means for detecting a defect on a surface to be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for inspecting defects on a surface to be inspected of a disc-shaped inspected object, and in particular, a gear or washer having a pattern on the surface and characters or a pattern drawn on the surface. CDs, records, coins, semiconductor wafers with patterns on the surface, lids of bottles and cans, etc. scratches, stains, pattern shifts on the surface with patterns and patterns drawn on the surface with disk-shaped objects, The present invention relates to an apparatus for inspecting a defect such as displacement of a hole provided at the center.

[0002]

2. Description of the Related Art Today, a defect inspecting apparatus for inspecting a disc-shaped inspected object for defects on a surface to be inspected, particularly a CD or record having a gear or washer having a pattern on the surface and characters or a pattern drawn on the surface. , Coins, semiconductor wafers with patterns drawn on the surface, bottles, can lids, etc. When inspecting for defects such as the displacement of the hole position, for example, in the inspection process of the manufacturing line, the inspection is performed mainly by the visual inspection of the inspector.

[0003]

The above-described visual inspection has a skilled technique. In addition, a large amount of inspected objects must be inspected for a long time, which causes the inspector to overlook defects or mistakes due to fatigue, and accurate inspection has not been performed. Further, even if a plurality of people are replaced at regular intervals, there is a cost due to personnel costs.

In recent years, due to the development of computer technology, an inspection apparatus using an image processing technology as shown in FIG. 9 can be considered. This is because the surface to be inspected of the disk-shaped objects to be inspected 92 arranged on the carrying device 91 is imaged by an imaging device (for example, a CCD camera) 93, image processing is performed by the image processing device 94, and the control unit 95 is controlled. Output an image signal. In the case of an inspection apparatus using image processing, it is necessary to distinguish a pattern and a defect on a surface to be inspected for inspection. Therefore, it is a general method that an image of a non-defective product is previously captured in the control unit and the difference between the image of the actually inspected product and that of the non-defective product is compared and inspected.

However, when the inspection object is a disk-shaped object and the pattern is drawn on the surface, the pattern does not always face a certain direction when the image is captured. For this reason, it is conceivable to inspect the inspection object before it is rotationally displaced, that is, to incorporate the inspection device inside the manufacturing apparatus for manufacturing the inspection object. However, it is often impossible to incorporate the inspection device due to the restriction of the internal space of the manufacturing device. Further, a method of transporting the inspection object without rotation deviation is conceivable, but the mechanism of the transportation device becomes complicated, resulting in an increase in cost. Furthermore, there is a method of removing the rotation of the pattern on a computer, but a dedicated circuit is required for high-speed processing, which lowers the throughput of inspection, and changes in processing contents depending on the cost of equipment and the type of inspection object. There's a problem.

[0006] Further, the difference in the illumination direction due to the rotational displacement also causes erroneous detection of a defect in a defect inspection by image processing.
In particular, when a complicated pattern is engraved on a surface such as a coin or a coin, a different illumination direction results in a completely different appearance. Circular illumination is also conceivable, but shadows of patterns required for image processing are erased, resulting in a decrease in contrast.

In view of the above-mentioned problems, the present invention is capable of effecting the defect inspection of an inspected object in which a pattern (pattern) is drawn on a circular inspected surface due to the rotation of the inspected surface. It is an object of the present invention to provide an inspection apparatus which can obtain a high-speed and stable detection accuracy without any problem, has a simple configuration, and can perform a defect inspection process at a low cost.

[0008]

According to a first aspect of the present invention, in an inspection apparatus for inspecting a defect on a circular inspection surface provided with a predetermined pattern, an image of the pattern on the inspection surface is predetermined. Imaging optical system (131,
133), a light detecting means (134) for one-dimensionally detecting the light from the surface to be inspected in the image plane, and an image of the surface to be inspected and the light detecting means are relatively rotated in the image plane. Rotating means (132), an image acquiring means (14) for forming an image based on a signal obtained from the light detecting means when the image of the surface to be inspected is relatively rotated with respect to the light detecting means, and the image acquiring means. The defect inspection apparatus is characterized by having a defect detection means (18) for detecting a defect on a surface to be detected by comparing the image obtained in (1) with image information stored in advance.

Since the light detecting means one-dimensionally detects the image of the surface to be inspected, the information of the surface to be inspected obtained at one time is one-dimensional. However, the image of the surface to be inspected and the light detecting means are one-dimensional. The image acquisition means accumulates one-dimensional information by relatively rotating and
As a result, information on the entire surface to be inspected is obtained. By comparing the image obtained in this way with the previously stored image, defects on the circular inspection surface can be easily inspected regardless of the rotational position of the inspection surface during inspection. can do.

According to a second aspect of the present invention, the above-mentioned defect detecting means has a memory in which an image obtained by the image acquiring means of the surface to be inspected in which a predetermined pattern is provided and which has no defect is stored. It is characterized in that the defect is inspected by comparing the image obtained at the time of the defect inspection with the image stored in the memory. This is to compare an image of a non-defective non-defective inspected surface with an image of the inspected surface to be actually inspected, so that the defect inspection can be accurately performed.

According to a third aspect of the present invention, in addition to illuminating the surface to be inspected, the direction of illumination to the surface to be inspected is changed by the relative rotation of the image of the surface to be inspected by the rotating means and the light detecting means. It is characterized by having an illuminating device for changing. As a result, the illumination from the fixed direction is realized with respect to the image of the surface to be inspected which is relatively rotated. According to a fourth aspect of the present invention, the illumination device includes a first polarization optical element, and the surface to be inspected is irradiated with illumination light through the first polarization optical element,
The image forming optical system is characterized by having a second polarization optical element and forming an image of the surface to be inspected on the image formation surface via the second polarization optical element. By arranging these polarization optical elements in the illumination device and the imaging optical system, it is possible to acquire an image and perform defect inspection without being affected by extra light such as flare light or diffused reflection light.

According to a fifth aspect of the present invention, the above-mentioned image acquisition means is based on rotation detection means for detecting a relative rotation amount between the image of the surface to be inspected and the light detection means, and a detection signal from the rotation detection means. It is characterized in that it has adjusting means for adjusting the time for accumulating the signal from the light detecting means. That is, the light from the surface to be inspected is accumulated until the image on the surface to be inspected and the light detecting means are relatively rotated by a predetermined amount. This makes it possible to always obtain an optimum image for the inspection process regardless of the type of object to be inspected or the shape of the pattern on the surface to be inspected.

According to a sixth aspect of the present invention, the rotating means is an image rotator arranged in the optical path of the imaging optical system, and the illuminating device is a light source and the light from the light source is inspected via the image rotator. An illumination optical system for irradiating the surface, and the illumination optical system is arranged at or near the pupil position of the illumination optical system, and shields the light from the light source near the optical axis of the illumination optical system. A light-shielding member that allows only light in a partial area decentered from the optical axis to pass therethrough is provided.

At the pupil position (pupil surface) of the illumination optical system, the light passing through the partial area decentered from the optical axis of the illumination optical system is radiated onto the surface to be inspected. Lighting (oblique lighting) is achieved. Since the illumination light has passed through the rotating means, the illumination light is always illuminated from a certain direction with respect to the image of the surface to be inspected, which rotates relative to the light detecting means.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION
An example of a coin defect inspection device having a pattern carved on the surface will be described. FIG. 1 is a block diagram showing a schematic configuration of an inspection apparatus according to the first embodiment of the present invention. A coin 12, which is an object to be inspected, is conveyed by a conveying device (hereinafter, referred to as “conveyor”) 11 from a coin manufacturing device (not shown), and is arranged below the image pickup unit 13 of the inspection device. The signal from the imaging unit 13 is constantly output to the image processing unit 14. Here, the coin 12 is positioned by the positioning device 17 so that the optical axis of the imaging unit and the center position of the coin coincide with each other. When the positioning device 17 finishes positioning the coin 12, the positioning device 17 outputs a positioning completion signal to the main control system 15. Upon receiving this signal, the main control system 15 outputs a control signal for capturing an image to the image processing unit 14. Upon receiving this control signal, the image processing unit 14 immediately starts accumulating the image signal from the imaging unit and shifts to image processing. Image processing by the image processing unit 14 will be described later in detail. The image signal from the image processing unit 14 is input to the defect detection unit 18, and the defect detection unit 18 determines whether or not the coin 12 is a good product based on the result of the image processing.
That is, it is determined whether or not there is a result such as a scratch or stain on the surface to be inspected of the coin 12. This judgment result is the main control system 1
Sent to 5. When the inspected coin 12 is defective, the main control system 15 issues a discharge signal to the discharge device 16. Upon receiving the discharge signal, the discharge device 16 discharges the defective coin from the conveyor 11. The defect detection unit 18 can also output to the main control system 15 information on the types of defects present in the defective coin, in addition to the results of the good and defective coins. The main control system 15 uses these defect detection units 1
The information from 8 is stored in the memory. The operator reads out the information in the memory in the main control system 15 using a terminal (not shown), so that the statistical processing such as the defect rate and the type of the defect can be performed.

FIG. 2 is a perspective view showing the structure of the image pickup section 13. As described above, the positioning device 17 mechanically positions the coin 12 with the two positioning rods 17a.
When the positioning is completed, the positioning rod 17a is moved to the conveyor 11
Evacuate from above. The coin 12 is illuminated by the illumination device 136. The image of the coin 12 is the objective optical system 13.
1 through the image rotation optical system 132 and the condensing optical system 133
An image is formed on the dimension line CCD 134. Objective optical system 13
1 and the condensing optical system 133 form an imaging optical system. The center of the one-dimensional line CCD 134 is the objective optical system 13.
1, the image rotation optical system 132 and the condensing optical system 133 are arranged on the optical axis AX of the imaging optical system. Therefore, the center of the positioned coin 12 is imaged at the center of the one-dimensional line CCD. The image rotation optical system 132 is composed of three mirrors 132a, 132b and 132c as shown in FIG. The image rotation optical system 132 is not limited to such a configuration and may be, for example, an image rotator (prism).

The image rotation optical system 132 is rotated at a constant speed about the optical axis AX by a motor (not shown). Therefore, the mirrors 132a to 132c rotate together. As the image rotating optical system 132 rotates, the image of the coin 12 formed on the one-dimensional line CCD 134 also rotates. When the image rotation optical system 132 rotates a half turn (180 °), the coin 1 imaged on the one-dimensional line CCD 134.
The image of 2 rotates one round (360 °). Therefore, when the image rotation optical system 132 rotates once (360 °), the image of the coin 12 rotates twice (720 °). The rotation of the image rotation optical system 132 is detected by the rotary encoder 137. The rotary encoder 137 outputs to the electric circuit 138 a pulse signal whose number is proportional to the amount of rotation of the image rotation optical system. The electric circuit 138 holds the signal (charge) output from the one-dimensional line CCD 134 and transfers the image signal to the image processing unit 14 when the rotary encoder 137 counts a predetermined number of pulses. And
The signal from the one-dimensional line CCD 134 is held until the rotary encoder 137 counts a predetermined number of pulses again. The user can adjust the hold time of the signal (charge) by this electric circuit via the main control system. By adjusting this time interval, it is possible to change the image acquisition conditions according to the type of object to be inspected and the shape of the pattern on the surface to be inspected, and it is possible to always obtain the optimum image for the inspection process.

Further, a first polarizing plate is provided inside the illuminating device 136, the coin 12 is irradiated with the illumination light through the first polarizing plate, and a second polarizing plate is also provided inside the condensing optical system 133. An image of the pattern may be formed on the one-dimensional line CCD via the second polarizing plate. With these polarizing plates, the pattern on the coin 12 can be imaged on the image plane with high contrast.

Further, as shown in FIG. 2, the illuminating device 136 has a rotating portion 139 provided at the tip of the objective optical system 131.
It is fixed to. Since the rotation unit 139 rotates at a constant speed around the optical axis AX by a motor (not shown) with respect to the objective optical system 131, the illumination device 136 also rotates around the optical axis AX. Rotation of image rotation optical system 132 and illumination device 136
Is controlled by the rotation control system 135.
The rotation control system 135 controls the illuminating device 136 to rotate twice as many times as the image rotating optical system 132 makes one rotation. By such rotation control, the coin 12 that rotates
Illumination from a certain direction is realized for the image of. This will be described with reference to FIG.

The left side of FIG. 4 shows the positional relationship among the inspection object (coin) 12, the mirror 132b, and the illuminating device 136 when the image pickup unit 13 is viewed from above, in a time series manner. Coin 12 imaged on CCD
The relationship between the image of FIG. As shown on the left side of FIG. 4, while the mirror 132b makes 1/8 and 1/4 turns, the illumination device 136 makes 1/4 and 1/2 turns. Mirror 132
When b makes a quarter turn, the image on the one-dimensional line CCD becomes 1 /
Rotate two laps. Here, looking at the relationship between the one-dimensional line CCD, the coin image, and the illumination direction of the illumination device, the coin image rotates with respect to the one-dimensional line CCD that is positionally fixed, With respect to the illumination direction of the device, the image is illuminated from one predetermined direction with respect to the one-dimensional line CCD. That is, as shown in FIG. 5, the positionally fixed one-dimensional line CCD 134 and the illumination device 136 are fixed.
Against, the coin 12 (or the image of the coin 12)
Is the same as rotating the (actually coin 1
2 is not rotated, but the image of the coin is rotated by the image rotation optical system). As a result, the one-dimensional line CC
The influence of the illumination direction of the illumination device on the image obtained by D can be reduced. Specifically, it is possible to improve the image processing accuracy by eliminating the influence of the unevenness of the shadow of the pattern (pattern) caused by the difference of the illumination direction and the unevenness of the illumination. In particular, when a coin has reliefs, grooves, holes, etc. on its surface, a stable image with high contrast can be obtained by casting a shadow.

Although the number of lighting devices is one in this embodiment, a plurality of lighting devices may be used. When the inspection object 101 is, for example, a washer used for a joint portion of a hydraulic hose, a flaw 100 extending in a radial direction as shown in FIG. In such a case, it is effective to illuminate from a direction perpendicular to the radial direction (tangential direction of the circumference) as shown in FIG. 10, and according to the present invention, illumination from this direction is possible over the entire circumference.

Here, in the present embodiment, the rotation control system 135 controls the rotation of the image rotation optical system 132 and the illumination device 136. However, when the image rotation optical system 132 makes one rotation, the illumination device 136 is rotated. Alternatively, the respective members may be mechanically linked and interlocked so as to rotate twice. Next, processing of an image obtained by the one-dimensional line CCD will be described. In this embodiment, as shown in FIG. 5, it is assumed that a coin having a letter "A" on its surface is inspected for defects. FIG. 6A shows a one-dimensional line CC when the image rotation optical system is rotated by 180 °.
It is an image obtained by D. At this time, the image of the coin 12 is rotated once around the one-dimensional line CCD. As can be seen from this figure, since the image of the disc-shaped test object is rotated and the images are acquired and arranged by the one-dimensional line CCD for each predetermined rotation amount, the image obtained by the image processing unit is rectangular, The pattern of "A" becomes a curved pattern. FIG. 6B is an image obtained when the image rotation optical system rotates 360 °, that is, when the image of the coin rotates twice around the one-dimensional line CCD 134.

In the present embodiment, the defect detection unit 18 stores a sample image of a good coin in advance.
Since this image is an image for one rotation, the image shown in FIG.
The image shown in (a) will be described below as a non-defective coin image 61 stored in advance in the defect detection unit 18. When actually obtaining an image of a coin to be inspected, since the coin has a rotation degree of 360 °, it is not possible to know where the captured image starts. Therefore, at the time of inspection, an image of two coins is obtained. The image shown in FIG. 6B will be described below as a coin image 62 acquired at the time of inspection. Since the image shown in FIG. 6 (b) has captured images of two coins, a portion corresponding to the sample image shown in FIG. 6 (a) always exists somewhere.

The defect detecting section 18 first compares the two images (the sample image and the inspection image) to determine where the sample image corresponds to the image captured during the inspection.
It is determined by the correlation of the images. FIG. 7A is a diagram when the correlation process is performed using the entire image. The defect detection unit 18 one-dimensionally scans the image 61 of the sample captured in advance from the upper side of the image 62 captured during inspection to obtain the correlation value, and the position with the highest value is the corresponding position. to decide. FIG. 7A shows a case where the correlation value becomes highest when the upper end of the image 62 acquired at the time of inspection and the upper end of the sample image 61 overlap.

Further, FIG. 7B is a diagram showing a case where the correlation processing is performed by using the characteristic part 63 of the sample image. The operator cuts out a characteristic portion 63 from the sample image captured in advance. Then, with respect to the image 62 obtained at the time of inspection, this cut-out partial image is one-dimensionally scanned in the direction of the arrow in the figure, and correlation processing is performed.
According to such correlation processing, the amount of calculation can be significantly reduced as compared with the above-described correlation processing performed on the entire screen.

When performing the partial correlation processing as described above,
The characteristic parts 63 may overlap at a plurality of locations. At this time, since there is a possibility of erroneous recognition, the defect detection unit 18 informs the operator that there are a plurality of candidates. Thus, the operator can change the position of the sample image and perform the correlation process again. Further, the user himself / herself may compare the sample image and the image of the inspection character and select an appropriate one from a plurality of candidates. Such processing can prevent erroneous recognition of the defect detection unit 18. Further, instead of the operator selecting from a plurality of candidate points, the defect detecting section 18 automatically expands the characteristic partial area and performs the partial correlation processing again (or repeatedly) to obtain a final accurate result. Correlation processing may be performed such that one location that overlaps with is searched.

In this way, the defect detecting section 18 obtains a portion of the image 62 acquired at the time of inspection, where the sample image 61 exactly overlaps. Next, the defect detecting unit 18 compares the sample image (image of good coin) with the image obtained at the time of inspection (image of coin of inspection product) at the position of the obtained image. As a comparison method, a difference value between two images is taken, and for example, if the difference value is a predetermined number or more in a pixel unit, it is determined that there is a defect, and an ejection signal is output to the ejection device. The determination of the presence / absence of a defect is not limited to the above, and various methods are conceivable depending on the inspection target and the item.

Now, in addition to the method of inspecting a defect by the correlation processing and the comparison processing between the sample image and the inspection image as described above, for example, the shape comparison method as disclosed in Japanese Patent Publication No. 4-52992. Alternatively, the defect inspection method may be used. Hereinafter, this inspection method will be briefly described. FIG. 8 is a diagram illustrating image processing by the shape comparison method. First, all the look-up table memories in the defect detection unit 18 are initialized to 0. Next, an image of a good coin is captured in advance, binarized, and scanned with a small window 81 as shown in FIG. This window 81 is composed of 4 × 4 elements. This one element may be one pixel or an element composed of a plurality of pixels. This depends on whether an area for storing the shape is made large (pattern recognition with a large field of view) or small (pattern recognition with a small field of view).

Next, the array of pixels in the window is converted into an address, and the address memory of the corresponding lookup table is changed from 0 to 1. This operation is performed in the direction of the arrow in FIG.
This is repeated while shifting the element, and the entire image is scanned. Then, the image is converted into a look-up table.
That is, the shapes of white (0) and black (1) in the 4 × 4 element shown in FIG. 8 are stored in the entire screen. The above steps are the learning steps.

Next, the inspection process will be described below. In the inspection process, a process of converting a shape to an address is similarly performed on the inspection object, and an operation of referring to a corresponding address is repeated. If 1 is written in the corresponding memory, it is good, and if 0, it is a defect. In FIG. 8, a window consisting of 4 × 4 elements, that is, a 16-bit address is used, but the present invention is not limited to this. In addition, by combining several pixels in the window into one element and changing the size of the entire window,
Defects of different sizes and qualities can be detected. Further, by performing inspection with a plurality of element sizes at the same time, it becomes possible to accurately detect defects.

According to the defect inspection by the shape comparison method as described above, the image captured at the time of inspection is not the two coins as shown in FIG. 6B, but the one coin as shown in FIG. 6A. Image is enough. Therefore, there is an advantage that the inspection processing speed is significantly increased. Further, even if the center of the coin is not accurately aligned with the optical axis AX, the distortion of the image due to the positional deviation can be absorbed during the image processing, so that the accuracy of the positioning device is not so required. End

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a diagram showing a schematic configuration of the inspection device according to the second embodiment. Members having the same functions as those in the first embodiment are designated by the same reference numerals, and the description of the members will be omitted. In the present embodiment, the illumination device 136 is not provided independently of the image rotation optical system 132, but the illumination light is applied to the image rotation optical system, and at the same time, the surface to be inspected is irradiated via the image rotation optical system. different.

Illumination light emitted from the light source 111 is reflected by a half mirror 117 via a lens 112, a turret plate 113 holding a plurality of diaphragms, a lens 114, a field diaphragm 115, and a lens 116, and a Pechan prism (Pechan prism). ) 118. With the half mirror 117, the optical axis of the illumination optical system including the lenses 112, 114 and 116, the turret plate 113, the field stop 115, and the half mirror 117 coincides with the optical axis of the objective optical system 131. With such a configuration, the illumination optical system (112-
Illumination according to 117) is coaxial epi-illumination and Koehler illumination. In this embodiment, the Pecan prism 118 is used as the image rotation optical system 132 of the first embodiment.
By rotating the Pecan prism 118, the image of the coin 12 is rotated with respect to the one-dimensional line CCD 134, as in the first embodiment.

The turret plate 113 is arranged at the pupil position (pupil surface) of the illumination optical system. This position corresponds to the objective lens 1
It is a position conjugate with the pupil plane of 31. As shown in FIG. 12, the turret plate 113 is provided with an opening 120 for allowing all the light from the light source reaching the pupil plane to pass therethrough, an annular opening 121, and a position decentered from the optical axis, each of which is arranged with respect to the optical axis. A first modified diaphragm 122 having four openings arranged at positions rotated by 90 ° and a second modified diaphragm 123 having two openings symmetrically arranged with respect to the optical axis are provided. By rotating the motor 119 shown in FIG. 11, the four diaphragms can be selectively arranged in the optical path of the illumination optical system and the centers of the respective diaphragms can be positioned on the optical axis.

A ring-shaped aperture 121, the first deformable diaphragm 12
2. By using the second deformable diaphragm 123, since the illumination light illuminates the coin 12 in a partial area decentered from the center of the optical axis, the coin is illuminated from an oblique direction. Such deformation diaphragms 121, 122, 12
By arranging 3 in the illumination optical system, the pattern of the coin 12 can be clearly imaged. Further, since this illumination is applied to the coin 12 via the Pecan prism 118, the coin 1 with respect to the one-dimensional line CCD 134 is
Since the illumination direction of the illumination light on the coin 12 changes with the rotation of the image of No. 2, the same effect as that of the first embodiment described above with reference to FIG. 4 can be obtained with a simple configuration.

These diaphragms 120, 121, 122, 1
23 is a pattern on the surface of the coin 12, the type of the coin 12,
Furthermore, it is possible to switch appropriately according to the type of the inspected object other than the coin. Further, the shape of the diaphragm is not limited to that shown in FIG. 11, and may be, for example, a diaphragm in which one circular opening is provided in a portion decentered from the optical axis, and the shape of the opening is not limited to the circular shape. Further, a diaphragm having a mechanism for changing the size of the diaphragm or a mechanism for changing the position of the diaphragm in the pupil plane may be used.

A polarization beam splitter may be used instead of the half mirror shown in FIG. The illumination light from the illumination optical system is converted into linearly polarized light by the polarization beam splitter, and the coin 12 is irradiated with the light. Since the illumination light reflected by the metal mirror surface of the coin 12 is reflected as it is, it is reflected by the polarization beam splitter and is reflected by the one-dimensional line CCD 134.
Does not reach. However, since the reflected light from the edge of the coin pattern or the foreign matter is scattered and the polarization is disturbed, a part of the light is transmitted through the polarization beam splitter and the one-dimensional line CC
Reach D134.

A λ / 4 plate may be arranged between the polarization beam splitter and the objective optical system. With such a configuration, the illumination light that has passed through the polarization beam splitter and the λ / 4 plate becomes circularly polarized light and is applied to the coin 12. When the illumination light is right-handed circularly polarized light, it is left-handed circularly polarized light by being reflected by the metal mirror surface of the surface to be inspected, becomes linearly polarized light at the λ / 4 plate, passes through the polarization beam splitter, and passes through the one-dimensional line CCD 13.
Reaches four. In this case, the loss of the light amount is 1/2 only at the first reflection, and the loss of the light amount can be smaller than that in the case of only the half mirror or the polarization beam splitter.

[0039]

EFFECTS OF THE INVENTION According to the present invention, a surface-like defect to be inspected of a disk-shaped object, particularly a gear or washer having a pattern on the surface, a CD or a record or a coin having characters or a pattern drawn on the surface, a pattern on the surface Depicted semiconductor wafers, bottles, cans, and other disc-shaped objects that have patterns or patterns drawn on the surface.Scratches, stains, misalignment of patterns, misalignment of the holes in the center, etc. The defect can be inspected stably, accurately, at high speed, and inexpensively with a simple structure without being affected by the rotation of the pattern due to the rotation of the inspection object.

According to the second aspect of the present invention, the image of the inspected surface of a non-defective non-defective product is compared with the image of the actually inspected surface, so that the defect inspection can be performed accurately. According to the present invention as set forth in claim 3, illumination from a fixed direction is realized with respect to the image of the surface to be inspected, which is relatively rotated, is not affected by illumination unevenness of illumination light, and does not erase necessary shadows of the pattern. A stable image with high contrast can be obtained.

According to the fourth aspect of the present invention, by disposing the polarization optical element in the illumination device and the imaging optical system, an image can be obtained without being affected by extra light such as flare light or irregular reflection light. , Defect inspection can be performed. In the fifth aspect of the present invention, the image acquisition condition can be changed according to the type of the object to be inspected and the shape of the pattern on the surface to be inspected, and an image optimal for the inspection process can be always obtained.

According to the sixth aspect of the present invention, the illumination light is always illuminated from a fixed direction with respect to the image of the surface to be inspected, which is rotated relative to the light detection means, with a simple structure. It is possible to obtain a stable image with high contrast without being affected by the unevenness of illumination and without erasing the shadow required for the pattern.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of an inspection apparatus of the present invention.

FIG. 2 is a perspective view showing a configuration of an image pickup unit in the first embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of an image rotation optical system according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an illumination direction of an illumination device for an image of an object and a one-dimensional line CCD.

FIG. 5 is a diagram for explaining detection of an image of an object by a one-dimensional line CCD.

FIG. 6A is a diagram showing a sample image stored in the image processing unit, and FIG. 6B is an image of a surface to be inspected obtained at the time of inspection.

FIG. 7A and FIG. 7B are diagrams illustrating the correlation processing by the image processing unit.

FIG. 8 is a diagram showing another example of the image processing and the defect inspection processing by the image processing unit.

FIG. 9 is a diagram illustrating a general defect inspection apparatus using image processing.

FIG. 10 is a top view illustrating a modified example of the illumination direction.

FIG. 11 is a diagram showing a schematic configuration of an inspection device according to a second embodiment of the present invention.

FIG. 12 is a diagram illustrating a diaphragm provided on a turret plate 113.

[Explanation of symbols]

 11 ... Conveyor 13 ... Imaging part 14 ... Image processing part 15 ... Main control system 16 ... Ejection part 17 ... Positioning device 18 ... Defect detection part 134 ... One-dimensional Line CCD 136 ... Lighting device 137 ... Rotary encoder 138 ... Electric circuit

Front page continuation (72) Inventor Naoyuki Kawakami 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (6)

[Claims] 1. An inspection apparatus for inspecting a defect on a circular inspection surface provided with a predetermined pattern, wherein the imaging optics forms an image of the pattern on the inspection surface on a predetermined imaging surface. A system, a light detecting means for one-dimensionally detecting light from the surface to be inspected in the image plane, and an image of the surface to be inspected and the light detecting means in the image plane relatively to each other. Rotating means for rotating, an image acquiring means for forming an image based on a signal obtained from the light detecting means when the image of the surface to be inspected is rotated relative to the light detecting means, and the image acquiring means A defect inspection apparatus comprising: a defect detection unit that detects a defect on the surface to be detected by comparing the obtained image with image information stored in advance. 2. The defect detection means stores the image obtained by the image acquisition means of the surface to be inspected in which the predetermined pattern is provided and has no defect, and the image obtained at the time of defect inspection is stored as the image. An apparatus according to claim 1, characterized in that the defect is inspected by comparing it with the captured image. 3. An illumination device that illuminates the surface to be inspected and changes the illumination direction to the surface to be inspected in accordance with the relative rotation of the image of the surface to be inspected by the rotating means and the light detecting means. An apparatus according to claim 1 or 2, comprising: 4. The illumination device has a first polarization optical element, illuminates the surface to be inspected with illumination light through the first polarization optical element, and the imaging optical system includes a second polarization optical element. The apparatus according to claim 3, further comprising: an image of the surface to be inspected is formed on the image forming surface via the second polarization optical element. 5. The rotation detecting means for detecting a relative rotation amount between the image of the surface to be inspected and the light detecting means, and the surface to be inspected based on a detection signal from the rotation detecting means. 5. The apparatus according to claim 1, further comprising adjusting means for adjusting a time interval for detecting the image of. 6. The rotating means is an image rotator arranged in the optical path of the imaging optical system, and the illuminating device comprises a light source and the surface to be inspected from the light source via the image rotator. And an illumination optical system for irradiating the illumination optical system onto the illumination optical system, wherein the illumination optical system is arranged at a pupil position of the illumination optical system, or in the vicinity thereof, and emits light in the vicinity of the optical axis of the illumination optical system among light from the light source. The device according to claim 3 or 4, further comprising a light blocking member that blocks light and transmits only light in a partial region decentered from the optical axis.