JPH0458902B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is useful for detecting surface defects (eaves,
The present invention relates to a device for detecting irregularities (irregularities, rust, etc.), and more specifically, to a device that irradiates the surface of a material to be inspected with a light beam such as a laser and inspects for defects based on the state of the reflected light.

[Prior art]

BACKGROUND OF THE INVENTION Various devices have been developed and put into practical use to accurately and quickly inspect defects on the surface of a material to be inspected, such as a steel plate.

For example, Japanese Patent Application Laid-open No. 10793/1986 includes a light receiver that receives only specularly reflected light from the surface of the material to be inspected and a light receiver that receives only diffusely reflected light, and by comparing the light reception results of both, An apparatus for detecting defects on the surface of a material to be inspected has been proposed.

In addition, in Japanese Patent Publication No. 59-33855, the distribution state of the reflected and scattered light from the surface of the material to be inspected is detected by detecting the reflected and scattered light from the surface of the material to be inspected using multiple photodetectors, and from this result, the distribution state of the reflected and scattered light from the surface of the material to be inspected is detected. A method for detecting defects has been proposed.

Furthermore, JP-A No. 51-31281 discloses a method in which reflected light from the surface of a material to be inspected is received by a plurality of photodetectors, and the output of each photodetector is detected via a separate variable gain circuit. The gain of each variable gain circuit is set so that the light reflected from the normal material surface is blocked.In other words, an electric filter is configured with multiple variable gain circuits, and thereby A device has been proposed that detects only reflected light caused by defects.

Furthermore, Japanese Patent Application Laid-Open No. 58-77642 discloses that by providing a light receiver that receives reflected light so that the amount of reflected light from a specific defect matches the amount of reflected light from a normal part, reflections caused by defects other than the specific defect can be reduced. A method of detecting light has been proposed.

[Problem that the invention seeks to solve]

As described above, various inventions have been proposed for the purpose of detecting defects on the surface of a material to be inspected. Since the light receiver and the light receiver that receives diffusely reflected light are each fixed, it is possible to deal with changes in the quality of the inspected material or changes in its condition that are not defects, such as changes in surface roughness due to differences in processing and finishing methods. It is necessary to replace each receiver or change the installation position. Therefore, although it is effective when detecting defects based on a certain normal state, it is not possible to quickly respond when the defect detection criteria is changed.

In the second invention of Japanese Patent Publication No. 59-33855, it is possible to detect changes in normal reflected light caused by changes in the material of the inspected material or differences in processing/finishing methods as reflected light caused by defects. To deal with this situation, the material of the material to be inspected,
It is necessary to know in advance the distribution state of reflected and scattered light depending on the processing/finishing method, etc., and adjust the positions of the plurality of light receivers each time.

In the invention of the third Japanese Patent Publication No. 51-31281, by appropriately changing and setting the gain of each gain circuit,
Although it is possible to deal with changes in material, etc., it is still necessary to check in advance the gain that should be set in each gain circuit according to the material of the material to be inspected, and readjust it each time. When detecting defects based on a normal state other than the normal state being investigated, it is necessary to interrupt the inspection process and readjust each time.

In the fourth invention of JP-A-58-77642, the "specific defect" here refers to a certain state that is not substantially a defect, in other words, a specific state change within a range that can be considered as a normal state. However, a "specific defect" that is not a substantial defect will be detected as a defect, and a "specific defect" that is not a substantial defect will be detected as a defect. When changing to a "specific defect" that is not a defect, it is necessary to check in advance the mounting angle position of the light receiver, etc., and reset it each time.

In this way, with devices and methods for detecting defects on the surface of inspected materials that have already been proposed, when a specific processing or finishing is applied to a specific material, in other words, the standard normal state is fixed. It is considered to be effective in cases such as those described above. However, it is either impossible to follow and respond to changes in conditions within a range that can be considered normal due to changes in materials, processing/finishing methods, etc., or even if it is possible to respond to changes in the condition of the inspected material in advance. It is necessary to investigate various conditions within the range that can be considered normal for the various materials and processing/finishing methods for each, and if these are reset each time, work efficiency will decrease. There is a problem with doing so. Furthermore, in devices and methods that use a large number of photodetectors, signal processing circuits, etc., the burden of accurate adjustment and maintenance becomes large, and it must be said that there are many problems in terms of economic efficiency and workability. I don't get it.

The present invention has been made in view of the above circumstances, and is applicable not only to inspected materials that have undergone specific processing and finishing to specific materials, but also when the material of the inspected material changes or when processed.・Even if the finishing method changes, for example, in the case of rolled materials, the condition of the surface of the rolled material changes over time due to the wear condition of the rolling rolls, or if it adheres to the surface of the material to be inspected. It is possible to respond to changes in oil film thickness over time without interrupting inspection work.
Another object of the present invention is to provide an apparatus for detecting defects on the surface of a material to be inspected, which can accurately detect defects by two-dimensionally detecting reflected light from the surface of the material to be inspected.

[Means for solving problems]

In the present invention, the reflected light from the surface of the material to be inspected is received as a two-dimensional image by an accumulation-type two-dimensional light receiver, and the time average value is determined. does not occur,
In addition, the time average value obtained by the two-dimensional light receiver is compared with the filter pattern set on the variable optical filter at that time, and if the difference is within a predetermined range, it is assumed that no major defect has occurred. The two-dimensional image obtained by the two-dimensional light receiver is set as a filter pattern on a variable optical filter, and the reflected light from the surface of the inspection material is projected onto this variable optical filter, so that only the reflected light due to defects is passed. The system is configured to detect defects on the surface of the inspected material.

The present invention provides an apparatus for inspecting defects on the surface of a material to be inspected by comparing the state of the reflected light from the surface of the material to be inspected of the irradiated light beam with the state of the reflected light from the normal surface of the material. , a light splitter that splits the reflected light of the light beam from the surface of the material to be inspected into two; and a storage type two-dimensional light receiver that receives and accumulates one of the reflected lights split by the light splitter as a two-dimensional image. a variable optical filter onto which the other reflected light split by the light splitter is projected; a photodetector that detects the light transmitted through the variable optical filter; and a photodetector based on the detection result of the photodetector. a defect determiner that determines defects on the surface of a material to be inspected; Compare the pattern of reflected light accumulated in the two-dimensional light receiver, and if the difference is within a predetermined range, the pattern of reflected light accumulated in the storage type two-dimensional light receiver is converted into a normal filter pattern. and a rewriting determination circuit that rewrites this as a filter pattern of the optical filter.

[Effect]

In the present invention, reflected light caused by a defect is detected based on the time average value of a pattern of a two-dimensional image of reflected light from the surface of a material to be inspected, which changes within a range that can be considered as a normal state over a predetermined period in the past. Therefore, even if the condition of the surface of the material to be inspected gradually changes due to changes in the surface of the rolled material due to wear of the rolling rolls or changes in the state of the oil film on the surface of the material to be inspected, it is not necessary to change the setting of the conditions or rework the material. Since the pattern of normal reflected light, which is the standard for defect detection, is automatically followed and changed without the need for adjustment, processing speed and inspection efficiency are improved, and economical efficiency, workability, and inspection accuracy are also improved. improves. Furthermore, even if there is a change in the quality of the material to be inspected or a change in the processing/finishing method, it is possible to reset the conditions by using the pattern of the two-dimensional image of the light reflected from the normal surface of the inspected material as a reference. It is possible to respond quickly without having to do so.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram of a signal processing system shown together with a schematic diagram of an optical system showing the configuration of a surface defect inspection apparatus according to the present invention.

In the figure, reference numeral 1 denotes an oscillator for a laser beam B as a light beam, and the laser beam B oscillated by this is given to a scanning optical system 2.

In this embodiment, the scanning optical system 2 is composed of a polygonal mirror 20, a reflecting mirror 21, etc.
The irradiation direction of the laser beam B is moved in a direction (main scanning direction) perpendicular to the moving direction (sub scanning direction) indicated by the white arrow. Therefore, laser beam B
is scanned in the main scanning direction by the scanning optical system 2, and is scanned in the sub-scanning direction by moving the inspected material 3 in the sub-scanning direction. In addition to the above-described configuration, the scanning optical system 2 may have a configuration using a vibrating mirror or the like.

The material to be inspected 3 is, for example, a rolled steel plate or the like, and the reflected light R of the laser beam B reflected from the surface thereof is incident on the light receiving optical system 4 .

The light receiving optical system 4 includes a condenser lens 40 that condenses the reflected light R of the laser beam B from the surface of the inspected material 3, and a condensing lens 40 that condenses the reflected light R of the laser beam B from the surface of the inspected material 3.
The reflected light R is then split into two directions using a half mirror or the like, one of which is directed onto the light receiving surface of the storage type two-dimensional light receiver 5, and the other onto the filter surface of the variable optical filter 8. It is composed of a light splitter 41 and the like, which respectively form an image on the light beam.

Specifically, the storage type two-dimensional light receiver 5 is, for example,
Consists of a combination of ITV camera and image memory,
ITV over a predetermined period of time preset as one period of the accumulation period signal SS as shown in FIG. 3a.
A two-dimensional image (specifically, its optical signal) received by the camera is stored in an image memory, and when a predetermined time has elapsed, a two-dimensional image pattern is output as the time average value. As shown in FIG. 2a, the accumulation type two-dimensional light receiver 5 having such a configuration receives a two-dimensional image of the reflected light R of the laser beam B, accumulates it for a predetermined period, and then calculates the time average value. is output to the read/write circuit 6.

The read/write circuit 6 is a storage type two-dimensional photodetector 5
The time average value output of the pattern of the reflected light R given by the storage type two-dimensional light receiver 5, that is, the electrical signal value of the two-dimensional image of the reflected light R from the surface of the inspected material 3 received by the storage type two-dimensional light receiver 5 over a predetermined period of time. This is shaped based on the average value to create a two-dimensional filter pattern as shown in FIG. 2e, for example. This newly created filter pattern is applied to the variable optical filter 8 stored in the read/write circuit 6 itself when the rewrite signal RRS is given from the rewrite determination circuit 7.
The filter pattern currently set for (previously,
A filter pattern created by the read/write circuit 6 and set in the variable optical filter 8,
The read/write circuit 6 itself still remembers it)
If the difference is within a predetermined range, it is applied to the variable optical filter 8 and the filter pattern is rewritten and reset to replace the previously set filter pattern. However, even if a new filter pattern is created after a predetermined period of time has elapsed, the rewrite determination circuit 7 will not send a rewrite signal.
If RRS is not given, and if the difference between the newly created filter pattern and the filter pattern set in the variable optical filter 8 at that point is greater than a predetermined range, the created filter pattern is variable. No rewriting or resetting of the optical filter 8 is performed.

As described above, the other of the reflected lights R of the light beam B split by the light splitter 41 is imaged on the variable optical filter 8 on its filter surface. This variable optical filter 8 is constructed by disposing a large number of liquid crystals or BSO (Bi ₁₂ SiO ₂₀ crystals) having an electro-photoelectric (Pockels) effect, and controlling each of them electrically and optically through transparent electrodes. It is configured such that a non-transparent or semi-transparent pattern of a desired shape, that is, a filter pattern, can be arbitrarily varied and set on the surface. As described above, the filter pattern to be set in the variable optical filter 8 is the filter pattern output from the storage type two-dimensional photodetector 5 when the rewrite signal RRS is given to the read/write circuit 6 from the rewrite determination circuit 7. The read/write circuit 6 shapes the time average value of the reflected light R to create a new filter pattern, compares this with the filter pattern currently set in the variable optical filter 8, and determines the difference within a predetermined range. If the value is within the range of 0 to 1, it is applied to the variable optical filter 8.

The condensing optical system 9 condenses the reflected light R after passing through the variable optical filter 8 and forms an image on the detection surface of the photodetector 10 .

The photodetector 10 detects the optical intensity of an optical image formed on its detection surface and converts it into an electrical signal. Therefore, the optical intensity converted into an electrical signal by this photodetector 10 is the reflected light R from the surface of the inspected material 3.
The optical intensity is obtained by subtracting the optical intensity of the portion corresponding to the filter pattern set in the variable optical filter 8 from the optical intensity of the variable optical filter 8.

The defect determiner 11 determines whether or not the electrical signal given from the photodetector 10 described above, in other words, the intensity of the light that has passed through the variable optical filter 8, is greater than or equal to a predetermined value. The presence or absence of a defect on the surface of the material 3 is determined, and if it is determined that a defect exists, a defect detection signal as shown in FIG. 3b is sent.
The ES is outputted to a predetermined display, storage device, etc. (not shown), and also outputted to the rewrite determination circuit 7.

The rewrite determination circuit 7 determines whether the filter pattern newly created by the read/write circuit 6 can be written into the variable optical filter 8 and reset. Specifically, the rewriting determination circuit 7 is configured as shown in FIG.
If defects occur frequently during one period of the accumulation period signal SS shown in FIG. The read/write circuit 6 determines that the light reception pattern of the reflected light R accumulated in the light receiver 5 is not a normal light reception pattern of the reflected light R.
The filter pattern is not reset to the variable optical filter 8, specifically, the rewrite signal RRS is not output, and if the defect occurrence is low during one cycle of the accumulation period, the defect determination device 11 If the output defect detection signal ES is less than the predetermined number of times,
The light reception pattern of the reflected light R accumulated in the storage type two-dimensional light receiver 5 during that period is compared with the filter pattern set for the variable optical filter 8 at that point in time, and the difference is within a predetermined range. If so, the light reception pattern of the reflected light R accumulated in the storage type two-dimensional light receiver 5 during that period is considered to be a normal light reception pattern of the reflected light R, and a rewrite signal RRS is given to the read/write circuit 6 to output the variable optical filter. 8 to reset the filter pattern.

Therefore, the filter pattern of the variable optical filter 8 is such that only when no defect is detected over one cycle of the accumulation period set as a predetermined period in the accumulation type two-dimensional light receiver 5, the reflected light during that period is determined. The average pattern of R is updated and set. That is, for example, in a case where the oil film thickness on the surface of the inspected material 3 gradually changes and the state of the reflected light R of the laser beam B gradually changes due to this, the filter set in the variable optical filter 8 Since the pattern also gradually changes as the thickness of the oil film on the surface of the inspected material 3 changes, it is not determined to be a defect. In addition, if the material of the inspected material 3 is changed and the pattern of the normal reflected light R changes greatly, for example, the two-dimensional pattern of the reflected light R of the inspected material 3 that is considered normal by visual inspection etc. The variable optical filter 8 uses the light reception pattern by the light receiver 5 as a normal pattern.
If set to , this filter pattern will be applied to the storage type two-dimensional photodetector 5 every time a predetermined period of time set as one cycle of the storage period has elapsed, unless defects occur frequently or large defects occur during that period. Since the pattern of the reflected light R is automatically reset to a normal pattern, there is no need to interrupt the inspection work each time to reset various conditions such as resetting the filter pattern, changing the position of the member, etc.

Next, the operation of the apparatus of the present invention configured as described above will be described below, according to the pattern of the reflected light R of the laser beam B shown in FIG. 2, a schematic diagram of the filter pattern, etc., and the timing chart shown in FIG. 3. explain.

The laser beam B oscillated and irradiated by the laser oscillator 1 is reflected by the mirror surface of the rotating polygonal mirror 20, further reflected by the reflecting mirror 21, and projected onto the surface of the inspected material 3. At this time, as the rotating polygonal mirror 20 rotates, the projection direction of the laser beam B moves in the main scanning direction perpendicular to the traveling direction of the inspected material 3, and as the inspected material 3 moves, the laser beam B moves in the sub-scanning direction. move in the direction.

Now, the reflected light R of the laser beam B from the surface of the inspected material 3 is condensed by the condenser lens 40, enters the light splitter 41, and is split into two.

One of the two-split reflected light R is imaged as a two-dimensional image on the light-receiving surface of the storage type two-dimensional light receiver 5,
The pattern is converted into an electrical signal and stored. By the way, when the surface of the inspected material 3 is normal with no defects and there is no oil film, the projected laser beam B is regularly reflected, so that the storage type two-dimensional light receiver 5 receives the reflected light R. The pattern is second
A pattern as shown in Figure a is shown. This light reception pattern is converted into an electrical signal and sent to a storage type two-dimensional light receiver 5.
Accumulated by

The storage type two-dimensional photodetector 5 time-averages the accumulation results of the electrical signals of the light reception pattern accumulated in the previous accumulation period in synchronization with the rise of the accumulation period signal SS as shown in FIG. 3a, which occurs at predetermined intervals. and outputs it to the read/write circuit 6.

When the read/write circuit 6 is given the output of the time average value of the light reception pattern from the storage type two-dimensional light receiver 5 as described above, it shapes this to create a filter pattern to be set in the variable optical filter 8. do. Specifically, a filter pattern as shown in FIG. 2e is created for the normal light reception pattern shown in FIG. 2a. That is, it blocks (or attenuates) the light rays in the portion where the amount of light received in the light receiving pattern of the light receiver 9 is above a predetermined amount, and passes the light rays in the portion where the amount of light received in the light receiving pattern of the light receiver 9 is less than the predetermined amount. By doing so, the read/write circuit 6 creates a filter pattern in which the cut-off portion is expanded by a certain width, taking into account the tolerance for fluctuations in the light receiving pattern within the accumulation period.

On the other hand, each time a new filter pattern as shown in FIG. 2e is provided to the variable optical filter 8 from the read/write circuit 6 as described above, this new filter pattern is set. Therefore, a pattern of reflected light R after passing through the variable optical filter 8, which is similar to the light reception pattern imaged on the storage type two-dimensional light receiver 5, enters the condensing optical system 9, and this is the light An image is formed on the detection surface of the detector 10.

The photodetector 10 receives light from the condensing optical system 9 and converts the amount of light received from an optical image formed on its detection surface into an electrical signal and outputs it to the defect determiner 11 .

The defect determiner 11 compares the level of the electrical signal given from the photodetector 10 with a predetermined level, and if the level is higher than the predetermined level, determines that a defect exists, and performs defect detection as shown in FIG. 3b. The signal ES is outputted to a display device or a storage device (not shown), and is also outputted to the rewrite determination circuit 7.

A case in which this defect detection signal ES is output will be specifically explained below. First, when reflected light R from a defect-free portion of the surface of the inspected material 3 enters the variable optical filter 8, the variable optical filter 8 receives a normal reflected light R as shown in FIG. 2e. Since the filter pattern is set, the amount of light passing through the variable optical filter 8 is very small or zero. For this reason, the defect determiner 1
1 does not output the defect detection signal ES.

However, defects on the surface of the inspected material 3, such as eaves,
The reflected light R pattern from the part where
As shown in FIG. b, a pattern is shown in which a component diffusely reflected by the eaves part is added to the normal pattern of reflected light R. Therefore, when the pattern of the reflected light R from this eaves part is projected onto the variable optical filter 8, which has a filter pattern corresponding to the normal reflected light R as shown in FIG. 2a, the pattern shown in FIG. As shown in FIG. 2, a pattern in which only the diffused reflection portion caused by the eaves has a relatively large amount of light is projected onto the light receiving surface of the photodetector 10, and its intensity is detected. In such a case, the defect determiner 11 assumes that the signal level provided from the photodetector 10 is higher than the predetermined comparison level set therein, and selects a high level as shown in FIG. 3b. Outputs defect detection signal ES.

On the other hand, the rewriting determination circuit 7 receives a defect detection signal from the defect determination device 11 in one cycle of each accumulation period.
The number of ES is counted, and if it has not reached a predetermined number or more at the end of each accumulation period, a rewrite signal is sent to the read/write circuit 6.
Output RRS.

If this rewrite signal RRS is not given, the read/write circuit 6 does not output the created new filter pattern to the variable optical filter 8, and therefore the variable optical filter 8 does not output the created new filter pattern to the variable optical filter 8. The filter pattern continues to be set. In addition, when the rewrite signal RRS is given from the rewrite determination circuit 7 to the read/write circuit 6, the read/write circuit 6 uses the filter pattern currently set in the variable optical filter 8 stored in itself and the current time. The newly created filter pattern is compared, and if the difference between the two is greater than a predetermined range, the new filter pattern created this time is not rewritten and set in the variable optical filter 8, and the difference between the two is determined to be within the predetermined range. Only when it is within the range, the newly created filter pattern is rewritten and reset to the variable optical filter 8.

Through such processing, a new filter pattern created including the pattern of reflected light R caused by a defect is not set on the variable optical filter 8, so that the variable optical filter 8 does not receive normal reflected light. This means that the R pattern is always set.

By the way, when the surface condition of the inspected material 3 gradually changes, for example when the inspected material 3 is a rolled steel plate, the inspected material 3 changes as the rolling rolls wear out.
A situation occurs in which the surface condition of a rolled steel sheet changes gradually. Alternatively, a situation may occur in which the surface of the material to be inspected 3 itself is normal, but the thickness of the oil film covering the surface varies. For example, Fig. 2c shows the pattern of the reflected light R when the thickness of the oil film on the surface of the inspected material 3 is relatively thick, but in such a case, the pattern of the reflected light R that should originally be circular. The outline of the image becomes slightly blurred. Therefore, when this pattern of reflected light R is projected onto the variable optical filter 8 having the filter pattern shown in FIG.
Although this is detected by the photodetector 10, the defect determiner 11 does not output the defect detection signal ES at this level of light intensity.

On the other hand, in the case described above, the storage type two-dimensional light receiver 5
A pattern of reflected light R with a slightly blurred outline as shown in FIG. Therefore, the average value output from the averaging unit 6 to the filter pattern generator 7 becomes a pattern having a slightly larger outline than the pattern of the reflected light R shown in FIG. 2a. However, with such a change in the amount of reflected light R, the defect detection signal ES is not outputted from the defect determination device 11, so the rewriting determination circuit 7 outputs the rewriting signal RRS. Therefore, in such a case, the read/write circuit 6 compares the filter pattern currently set in the variable optical filter 8 with the newly created filter pattern, and determines if the difference is greater than a predetermined range. If so, the filter pattern is not rewritten and reset, and the variable optical filter 8 is changed only when the difference is within a predetermined range.
Rewrite and reset the filter pattern to the newly created filter pattern. Therefore, when the filter pattern of the variable optical filter 8 is rewritten and reset, a new filter pattern having a slightly larger outline than the normal filter pattern shown in FIG. 2a is set on the variable optical filter 8. For this reason, the filter pattern set for the variable optical filter 8 is such that the reflected light R gradually changes due to changes in the oil film thickness even though the surface condition is normal.
Since it changes so as to follow the pattern of , it is not determined that there is a surface defect on the material to be inspected 3.

FIG. 2d shows a pattern of reflected light R from the surface of the inspected material 3, which has directionality on the surface. In such a material to be inspected 3, the pattern of the reflected light R takes on an elliptical shape according to the directionality of the surface of the material to be inspected 3. If the material, etc. of the inspected material 3 is changed and the pattern of the reflected light R from the surface of the inspected material 3 which is normal, that is, has no defects, changes significantly, the inspected material At the first time when the material of the inspection object 3 is changed, the pattern of the reflected light R from the normal surface of the inspection object 3 is read by the storage type two-dimensional light receiver 5, and this is used as a new filter pattern by the variable optical filter 8. You can set it to . This makes it possible to immediately perform inspection work without having to perform troublesome resetting and adjustment of various conditions, including resetting the filter pattern of the variable optical filter 8, or changing the position of each member. .

〔effect〕

As described above, in the present invention, the pattern of the reflected light of the laser beam, which is the standard for determining the presence or absence of defects, changes according to changes in the surface of the inspected material within a range that can be considered normal. There is no need to reset or adjust various conditions of the equipment in response to changes in the oil film on the material surface or changes in the surface condition of the material to be inspected due to wear of rolling rolls in the case of rolled steel plates. Alternatively, even if the processing/finishing method has been changed, it can be handled easily and quickly by simply setting the pattern of reflected light from the normal surface of the inspected material as the filter pattern of the variable optical filter. It is possible.
Therefore, according to the present invention, defects on the surface of a material to be inspected such as a rolled steel plate can be detected efficiently and economically with a relatively simple device configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the signal processing system shown together with a schematic diagram of the optical system of the device of the present invention, Fig. 2 is a schematic diagram of the reflected laser beam and filter pattern, and Fig. 3 is a schematic diagram of the reflected light of the laser beam and the filter pattern.
The figure is a timing chart of the signal processing system. B... Laser beam, R... Reflected light, 1... Laser beam oscillation device, 2... Scanning optical system, 3...
Material to be inspected, 4... Light-receiving optical system, 5... Storage type two-dimensional light receiver, 6... Read/write circuit, 7...
Rewriting determination circuit, 8... Variable optical filter, 9...
. . . Condensing optical system, 10 . . . Photodetector, 11 . . . Defect determiner.

Claims (1)

[Claims] 1. Inspecting defects on the surface of a material to be inspected by comparing the state of reflected light of the irradiated light beam from the surface of the material to be inspected and the state of the reflected light from a normal material surface. The apparatus comprises: a light splitter that splits the reflected light of the light beam from the surface of the material to be inspected into two; and an accumulation type that receives and accumulates one of the reflected lights split by the light splitter as a two-dimensional image. a two-dimensional light receiver; a variable optical filter onto which the other reflected light split by the light splitter is projected; a photodetector that detects the light transmitted through the variable optical filter; and detection of the photodetector. a defect determiner that determines a defect on the surface of a material to be inspected based on the results; Compare the pattern of reflected light accumulated in the storage type two-dimensional light receiver and if the difference is within a predetermined range, the pattern of reflected light accumulated in the storage type two-dimensional light receiver is normalized. 1. A surface defect inspection device comprising: a rewriting determination circuit for rewriting the filter pattern as a filter pattern of the optical filter.