JP2009002669A - Visual inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visual inspection device capable of quickening inspection. <P>SOLUTION: The correspondence of a luminous energy controlled variable to reference lightness is found as a light source characteristic in a light source characteristic measuring part 135 of an image processing part 13, and is stored as a light source characteristic data in a light source information storage part 136. In the inspection, the inspection is executed quickly without requiring labors and times for regulating luminous energy, by computing the luminous energy controlled variable, based on a lightness converted value when registering a correct answer pattern, and the light source characteristic data therein. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an appearance inspection apparatus, and is particularly suitable for application to defect inspection of integrated circuits and printed circuit patterns on a semiconductor wafer.

In an appearance inspection apparatus that picks up an image of an inspection object and determines a defect of the inspection object based on the image, maintaining an appropriate illumination condition for illuminating the inspection object is an important issue for improving the accuracy of the quality determination. . Therefore, conventionally, there has been proposed a method of automatically adjusting the amount of illumination light so that the inspection object is always illuminated under the illumination conditions suitable for the inspection, regardless of variations in the illumination characteristics.
For example, in Patent Document 1, the brightness of an image obtained by imaging an inspection target is obtained, and when the brightness is not at a predetermined brightness level (level optimal for inspection), a method of adjusting the amount of illumination light is used. Proposed. In this method, for an object having the same reflection characteristic as the inspection object, the reflection characteristic is obtained in advance by changing the amount of illumination light and imaging a plurality of times, and based on the reflection characteristic during actual measurement of the inspection object. The amount of illumination light necessary to obtain a predetermined brightness level is calculated.

Further, in Patent Document 2, the reflected light when the non-defective product to be inspected is adjusted in advance to an illumination light amount that can be imaged under appropriate conditions, and the standard reflection object different from the inspection object is illuminated with the illumination light amount. A method has been proposed in which the brightness is stored, and at the time of inspection, the inspection is executed after adjusting the illumination light quantity so that the brightness is stored by illuminating the standard reflector first.
JP 2001-66120 A JP 2004-184242 A

  However, the conventional method disclosed in Patent Document 1 requires that the inspection target is a homogeneous surface, and a defect to be determined can be detected locally in a test image such as a foreign object or a flaw on the surface. Although it is effective in the apparatus, it is not suitable for an inspection apparatus such as an IC chip that compares patterns and determines pass / fail based on the pattern difference. This is because, in such an inspection method, the illumination conditions should be the same when the correct pattern is imaged and when the inspection object is imaged. If the light intensity is adjusted according to each inspection object, the correct answer and the inspection object And the difference may increase. In addition, even if the object to be inspected is a homogeneous surface, if the surface state itself is the object to be inspected, for example, a composition having a reflectance different from that of the original surface layer, such as when an IC chip mask is defective. If the amount of light is adjusted for a defect whose layer is exposed on the surface, an abnormality in the reflectance cannot be detected. This is because, in the method of Patent Document 1, when the brightness does not reach a predetermined level at the time of inspection, it is caused by a change in the reflectance of the inspection object, or a change in illumination characteristics due to deterioration, illumination replacement, or the like. The cause is that it is not possible to determine whether the problem is caused. In addition, if there is something like a large stain on the inspection object, or there are many foreign objects or scratches, and the brightness cannot be detected correctly from the image to be inspected, incorrect adjustments will be made. there is a possibility.

On the other hand, in the method of Patent Document 2, since the adjustment amount of the illumination light is not affected by the state of the object at the time of inspection, the illumination conditions of the inspection object can be made the same as when the correct pattern is captured. However, in this method, in order to reproduce the illumination light quantity at the time of imaging a non-defective product, a procedure for adjusting the light quantity by illuminating the standard reflector before the inspection is necessary, which hinders the speeding up of the inspection. In particular, when an object with a complex pattern is divided into several fields of view, such as in the surface inspection of an IC chip, and the illumination light quantity differs in each divided field of view, In addition, it is necessary to make adjustments with standard reflectors, which is a problem when it is desired to perform inspection at high speed.
Therefore, an object of the present invention is to provide an appearance inspection apparatus capable of reproducing the same illumination conditions as those at the time of registering a correct pattern without performing a procedure for adjusting the amount of light by illuminating a standard reflector for each inspection object during imaging of the inspection object. Is to provide.

In order to solve the above-described problems, according to the appearance inspection apparatus according to claim 1, the quality of the inspection object is determined based on a comparison of images obtained by imaging the non-defective product and the inspection object under the illumination condition by the light source. In appearance inspection equipment,
The reference brightness that is the brightness of the reference surface when the reference surface that substitutes the light receiving surface to be inspected is illuminated by the light source, and the light amount control amount that is the operation amount for the light source for controlling the light amount of the light source A light source characteristic measurement unit that obtains the relationship as a light source characteristic;
A reference brightness acquisition unit for registration that acquires the reference brightness under illumination conditions during non-defective imaging as the reference brightness for registration;
A light amount control amount calculation unit for calculating the light amount control amount necessary to obtain the registration-time reference brightness on the reference surface based on the light source characteristics;
An illumination controller that controls the light amount of the light source at the time of imaging of the inspection object, according to a calculation value by the light amount control amount calculation unit;
It is characterized by providing.
Here, the reference brightness is the brightness of the light reflected at least on the reference plane until the light output from the light source is imaged. For example, the brightness of the reference plane may be measured. The illuminance of the captured image may be used.

According to the appearance inspection apparatus of the second aspect of the present invention, in the first aspect, the registration-time reference brightness acquisition unit sets the light amount control amount during the non-defective imaging to the reference brightness based on the light source characteristics. The reference brightness at the time of registration is obtained by conversion.
According to the appearance inspection apparatus of claim 3 of the present invention, in claim 1 or 2, comprising a light source characteristic storage unit that stores the light source characteristic measured by the light source characteristic measurement unit,
The light quantity control amount calculation unit performs the calculation based on the light source characteristic stored in the light source characteristic storage unit, so that the measurement for a plurality of inspection objects is performed for one measurement by the light source characteristic measurement unit. The operation is configured to be repeatable.

According to the appearance inspection apparatus according to claim 4 of the present invention, in any one of claims 1 to 3, the image pickup position of the inspection object is provided with a transport unit that relatively moves the reference plane instead of the inspection object. It is characterized by.
According to the visual inspection apparatus of the fifth aspect of the present invention, in any one of the first to fourth aspects, the light source characteristic measurement unit is a plurality of images obtained by imaging the reference plane by changing a light amount of the light source. The light source characteristic is obtained based on data.

According to the appearance inspection apparatus according to claim 6 of the present invention, in the appearance inspection apparatus for determining pass / fail of the inspection object based on comparison of images obtained by imaging the non-defective product and the inspection object under the illumination condition by the light source,
A light source characteristic measurement unit for obtaining a relationship between a reference brightness that is a brightness of a reference surface when the reference surface that is substituted for the light receiving surface to be inspected is illuminated by the light source and a light amount of the light source, as a light source characteristic;
A reference brightness acquisition unit for registration, which acquires the reference brightness under illumination conditions during non-defective imaging as a reference brightness for registration;
Based on the light source characteristics, a light amount calculation unit that calculates the light amount of the light source necessary for obtaining the reference brightness at the reference plane on the reference surface;
An illumination controller that controls the light amount of the light source at the time of imaging of the inspection object in accordance with a calculation value by the light amount control amount calculation unit;
It is characterized by providing.
In this way, the light source characteristics may be obtained from the light amount and the reference brightness.

  As described above, according to the present invention, the relationship between the light quantity control amount and the reference brightness is obtained in advance as the light source characteristic, and the light quantity is adjusted by illuminating the standard reflector for each inspection object when imaging the inspection object. Without performing the procedure, it is possible to reproduce the same illumination conditions as when capturing the correct pattern. For this reason, it is possible to speed up the inspection.

Hereinafter, an appearance inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. This appearance inspection apparatus can be used, for example, for detecting a defect in a pattern of a printed circuit board.
(1) Configuration FIG. 1 is a diagram showing a schematic configuration of an appearance inspection apparatus according to the present embodiment ((a) is a schematic configuration of the entire apparatus, and (b) is a schematic configuration).
In FIG. 1, the appearance inspection apparatus includes an imaging unit 11, a conveyance unit 12, an image processing unit 13, an overall control unit 14, a user interface unit 15, and a storage unit 16.
The imaging unit 11 has a function of imaging the surface of the inspection target 100. Specifically, the imaging unit 11 images the inspection object 100 and the like placed at the imaging position, generates an image signal, a light source 112 that illuminates the inspection object 100, and a light amount from the light amount control amount calculation unit 137. The illumination controller 113, the illumination optical system 114, and the objective lens 115 are configured to control the light amount of the light source 112 in accordance with an instruction value of a control amount (described later). FIG. 1 shows an example of vertical epi-illumination.

  The transport unit 12 has a function of moving the inspection object 100 and the brightness reference plane 123 to the imaging position. Specifically, an XY stage 121, a stage controller 122 that drives and controls the XY stage 121 in accordance with a conveyance instruction from the overall control unit 14, and a brightness reference plane 123 are configured. The brightness reference plane 123 corresponds to the reference plane of the present invention, and is arranged together with the inspection target 100 on the horizontal plane of the XY stage 121, and is imaged instead of the inspection target 100 by being conveyed in the horizontal direction. Placed in position. In addition, the brightness reference surface 123 is a surface having uniform characteristics with respect to light such as reflectance and transmittance in the present embodiment, and is the same height as the illumination light receiving surface (surface) of the inspection target 100 on the XY stage 121. Is formed.

The image processing unit 13 has a function of determining pass / fail of the surface to be inspected by image processing based on the image signal output from the image sensor 111.
Specifically, as illustrated in FIG. 1B, the image processing unit 13 includes an AD conversion unit 131 and a correct pattern image storage unit that stores image data obtained by imaging a non-defective product for comparison with an inspection target as a correct pattern. 132.
In addition, the image processing unit 13 compares the inspection image storage unit 133 that stores image data obtained by imaging the inspection target (hereinafter also referred to as an inspection image), the correct pattern and the inspection image, and whether there is a defect to be inspected. It is configured to include a determination unit 134 that determines whether or not. In the determination by the determination unit 134, a known method such as a feature extraction method or a pattern matching method can be used.

  Further, the image processing unit 13 obtains the light source characteristic measurement unit 135 that obtains the light source characteristic based on the image data obtained by capturing the brightness reference plane 123 a plurality of times by changing the light amount of the light source 112 and the light source characteristic measurement unit 135. And a light source information storage unit 136 for storing light source characteristics and brightness conversion values (described later). Further, the image processing unit 13 calculates a brightness conversion value based on the light amount control amount and the light source characteristics when the correct pattern image is adjusted to the optimum brightness, thereby registering reference brightness (described later). Is provided with a reference brightness acquisition unit 138 for registration. Furthermore, a light amount control amount calculation unit 137 that calculates a light amount control amount of the light source 112 and sets the light amount control amount in the illumination controller 113 is provided. The image processing unit 13 may be configured by a program executed by a processor, a set of hardware circuits, or a combination of software and hardware, for example.

  The overall control unit 14 controls each unit to execute the inspection operation according to the present embodiment. In addition, the user interface unit 15 has a function of accepting an instruction to start or end an inspection from the user, or notifying the user of an inspection status or an inspection result. For example, it can be configured by a personal computer interface such as a monitor, a mouse and a keyboard, a touch panel, a combination of a button and an LCD display (liquid crystal display), or the like. The storage unit 16 stores a procedure for executing the inspection operation by the overall control unit 14 and data necessary for each process. The overall control unit 14 can be configured by a computer, and stores a control program in the storage unit 16 and reads it at the time of execution to execute the inspection operation according to the present embodiment.

(2) Operation Next, the operation of the appearance inspection apparatus according to the present embodiment will be described.
FIG. 2 is a flowchart showing the operation of the appearance inspection apparatus.
When performing inspection with this apparatus, first, light source characteristic measurement processing is performed prior to inspection (step S001). Here, FIG. 3 shows a configuration necessary for the light source characteristic measurement process. In the light source characteristic measurement process, specifically, the brightness reference surface 123 is arranged at the focal position of the objective lens 115 by the transport unit 12. Next, after the light amount of the light source 112 is adjusted by the illumination controller 113, the brightness reference plane 123 placed under the illumination condition is imaged by the image sensor 111, and the image signal is converted to the AD conversion unit 131 of the imaging unit 11. To convert to image data. Subsequently, the light source characteristic measurement unit 135 calculates the brightness (reference brightness) of the brightness reference surface 123 from the image data, and stores the correspondence with the current light amount control amount set in the illumination controller 113.

The reference brightness can be obtained as, for example, the brightness (cd / m ² ) of the brightness reference surface 123, the illuminance (lx) of the image, and the like. The light amount control amount here means an operation amount with respect to the light source for controlling the light amount of the light source 112, and varies depending on the configuration of the light source 112. For example, when the light amount of the light source 112 changes according to the magnitude of voltage or current, the voltage value or current value can be used as the light amount control amount, and the output level (for example, the ratio of output to the maximum output) ) Etc. can also be used as the light quantity control amount.
Then, this operation is executed a plurality of times while changing the light amount control amount, and based on the obtained pairs of the reference brightness and the light amount control amount, the light source characteristic measurement unit 135 calculates the light source characteristic data, The information is stored in the light source information storage unit 136.

4 and 5 are graphs showing examples of light source characteristic data.
As shown in FIG. 4, the light source characteristic data may be a look-up table in which the light amount control amount is finely changed in a specific range and associated with the reference brightness. Further, as shown in FIG. 5, on the premise that only the region where the light source characteristic is linear is used, parameters for linear approximation (for example, the approximate expression in FIG. 5) are obtained from measurement data obtained by changing the light amount control amount several times. And may be used as light source characteristic data. If the light source 112 can model not only the linear portion but also the light source characteristic curve as a curve, the model parameter may be used as the light source characteristic.
After completion of the light source characteristic measurement processing, correct pattern registration processing is performed (steps S101 to S104). Here, FIG. 6 shows a configuration necessary for correct pattern registration processing.

  In the correct pattern registration process, first, in step S101, a non-defective product to be inspected is imaged and adjusted to an optimal amount of light for the inspection. Specifically, a non-defective product 100 (hereinafter referred to as a non-defective sample 100 ′), which has been determined to have no defects in advance, is placed on the XY stage 121 and conveyed to the focal position of the objective lens 115 of the imaging unit 11. This good product sample 100 ′ is picked up by the image sensor 111, the image signal is converted into image data by the AD conversion unit 131, and temporarily stored in the correct pattern image storage unit 132. Next, brightness is calculated from the captured correct pattern image, it is determined whether the brightness is optimal for the inspection, and if it is not optimal, a correction amount that is optimal is obtained, and the light amount control amount calculation unit 137 Thus, the light amount control amount corrected with the correction amount is set in the illumination controller 113. Here, the determination of whether or not the brightness is optimal for the inspection is performed, for example, by determining whether or not the maximum brightness in the image (the brightness of the brightest area in the image) is within an appropriate range. With the corrected light quantity control amount set, the non-defective product sample 100 'is imaged again, and the obtained image data is temporarily stored in the correct pattern image storage unit 132, so that the brightness is optimal for inspection. Determine. This procedure is repeated until the optimal amount of light for inspection is obtained.

Next, in step S <b> 102, the image captured with the optimum light amount is stored in the correct pattern image storage unit 132 as the final correct pattern image.
In step S103, the registration reference brightness acquisition unit 138 obtains a brightness conversion value based on the light amount control amount obtained when the optimum light amount is obtained in step S102 and the light source characteristic obtained in step S001. It is stored in the light source information storage unit 136 in association with the pattern image. The association is performed, for example, by adding a common identification number to the correct pattern image and its brightness converted value.

FIG. 7 is a graph illustrating a method for calculating the brightness conversion value.
FIG. 7 is a graph of the light source characteristics obtained in step S001, and the reference brightness L0 corresponding to the light quantity control amount I0 when the optimum light quantity is obtained in step S102 is the brightness conversion value obtained here. That is, the brightness conversion value is the reference brightness (registration reference brightness) when the brightness reference plane 123 is illuminated with a light amount when an image optimal for inspection is obtained.
In step S104, it is determined whether correct pattern image data and brightness conversion values have been acquired for all types of correct patterns to be stored. If there is an unacquired correct pattern (step S104: No), step S101 is performed. Returning to step S101, the operations in steps S101 to S104 are repeated until acquisition of all correct patterns is completed.

In the repetitive operations of steps S101 to S105, the light source characteristic data is calculated in advance in step S001. Therefore, in order to obtain the brightness conversion value when the optimum light amount is obtained in step S102, the illumination target is determined to be a non-defective product. It is not necessary to change the sample to the brightness reference plane 123 and illuminate the brightness reference plane 123 with the light amount control amount to acquire the brightness, and quickly convert the brightness from the light amount control amount and the light source characteristic data. A value can be obtained. Therefore, correct pattern registration can be performed quickly.
When the above process is completed, an actual inspection process is executed (steps S301 to S306). Here, FIG. 8 shows a configuration necessary for the inspection process.
In the inspection, first, in step S301, the light amount control amount calculation unit 137 calculates a light amount control amount that reproduces the correct pattern registration time based on the light source characteristics and brightness converted values stored in the light source information storage unit 136. .

FIG. 9 is a graph illustrating a method for calculating the light amount control amount.
FIG. 9 is a graph of the light source characteristics obtained in step S001. As shown in FIG. 9, the optimal light quantity control amount I for inspection is a brightness conversion value stored in the light source information storage unit 136, and is an inspection target. From the brightness conversion value L of the correct answer pattern image to be compared with 100, a back calculation is performed.
In the subsequent step S302, the calculated light amount control amount I is set in the illumination controller 113. In the subsequent step S303, the inspection object 100 is imaged with the optimum light amount control amount I. In the subsequent step S304, the image processing unit 13 The image data of the inspection object 100 is compared with the correct pattern image data, and the presence or absence of the defect of the inspection object 100 is determined.

  The above operation is repeated until it is determined that all the inspection objects 100 or all the portions of the inspection object 100 have been inspected (step S305: Yes). When the type of the inspection object 100 is changed or when the part of the inspection object 100 is changed (step S306: Yes), that is, when the type of the correct pattern image to be compared is changed, the process returns to step S301 for inspection. The optimal light amount control amount is calculated again, imaging is performed, and comparison determination is performed (steps S302 to S306). On the other hand, when there is no change in the type (step S306: No), the process proceeds to step S303, imaging is performed with the light amount as it is, and a comparison determination is made (steps S303 to S306).

  It should be noted that periodic maintenance of the apparatus and replacement of parts of the light source 112, and the configuration of the illumination optical system 114 and the light source 112 are changed, so that when correct patterns are registered (steps S101 to S104) and during inspection (steps). If the light source characteristics change in S301 to S306), the light source characteristics are updated as shown in step S201. The processing content is the same as in step S001, and the data in the light source information storage unit 136 is updated with the acquired light source characteristic data. Thereby, even if the light source characteristic changes, the illumination condition optimal for the inspection can be reproduced.

(3) Operational Effects and Others As described above, in the present embodiment, the brightness conversion value is stored for the correct pattern image so that the same brightness as the brightness conversion value can be obtained on the brightness reference plane 123 at the time of inspection. Adjust the light intensity control amount. For example, when trying to make the illumination conditions the same by simply making the light amount control amount the same at the time of registering the correct pattern and at the time of inspection, for example, the light source characteristics of the light source 112 may change due to deterioration over time, or the light source 112 and the illumination optical system If the configuration is changed, the same light amount cannot be obtained even if the light amount control amount is the same, so the illumination conditions cannot be made the same, and the light source characteristics of the light source 112 do not change at all. Defect detection accuracy is reduced. On the other hand, in the present embodiment, since the illumination conditions at the time of correct pattern registration and inspection are matched with the brightness on the brightness reference surface 123 as a reference, even when the light source characteristic changes, it is exactly the same as at the time of registration. Illumination conditions can be reproduced and inspection can be performed with high accuracy. Further, by using the brightness of the brightness reference surface 123 as a reference, the illumination conditions can be matched regardless of the difference in the reflection characteristics of the inspection object 100.

In addition, since the relationship between the light quantity control amount and the reference brightness is obtained in advance as a light source characteristic, and the light quantity control amount is calculated backward based on the light source characteristic and the reference brightness, the brightness reference plane 123 is set for each inspection object at the time of inspection. It is not necessary to adjust the amount of light by illuminating, and it is possible to speed up the inspection when inspecting a plurality of patterns.
The application of the present invention is not limited to the above embodiment.
For example, calculating the brightness conversion value based on the light source characteristics at the time of registration is not an essential configuration in the present invention, and illuminates the brightness reference plane 123 when an optimal light amount is obtained from the correct pattern image. The reference brightness at the time of registration may be acquired. However, by obtaining the brightness conversion value from the light source characteristics even at the time of registration, the procedure for obtaining the brightness by illuminating the brightness reference plane 123 can be omitted as described above, so that the inspection can be further speeded up.

  Also, the correspondence between the light quantity and the light quantity level (for example, the ratio of the output light quantity with respect to the maximum output light quantity) and the reference brightness is obtained as the light source characteristic, and it is necessary to obtain the brightness of the brightness conversion value based on the light source characteristic. The light amount may be calculated backward and the illumination controller may control the light amount of the light source 112 to be a calculated value. In this case, the illumination controller may be configured to further calculate a light amount control amount such as a voltage value or a current value from the calculated value to control the light amount of the light source 112, or to detect the light amount in the vicinity of the light source 112 for the purpose. It may be configured to control the amount of light.

It is a schematic block diagram of the external appearance inspection apparatus concerning this embodiment. It is a flowchart which shows operation | movement of an external appearance inspection apparatus. It is a figure which shows a structure required for a light source characteristic measurement process. It is a graph which shows an example of light source characteristic data. It is a graph which shows an example of light source characteristic data. It is a figure which shows a structure required for a correct pattern registration process. It is a graph explaining the calculation method of a brightness conversion value. It is a figure which shows a structure required for an inspection process. It is a graph explaining the calculation method of light quantity control amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Inspection object 11 Image pick-up part 111 Image sensor 112 Light source 113 Illumination controller 114 Illumination optical system 115 Objective lens 12 Conveyance part 121 XY stage 122 Stage controller 123 Brightness reference plane 13 Image processing part 131 AD conversion part 132 Correct pattern image preservation | save part 133 Inspection image storage unit 134 Determination unit 135 Light source characteristic measurement unit 136 Light source information storage unit 137 Light quantity control amount calculation unit 138 Registration reference brightness acquisition unit (calculation of brightness conversion value)
14 Overall control unit 15 User interface unit 16 Storage unit

Claims (6)

In the appearance inspection apparatus for determining the quality of the inspection object based on the comparison of the images obtained by imaging the non-defective product and the inspection object under the illumination condition by the light source,
The reference brightness that is the brightness of the reference surface when the reference surface that substitutes the light receiving surface to be inspected is illuminated by the light source, and the light amount control amount that is the operation amount for the light source for controlling the light amount of the light source A light source characteristic measurement unit that obtains the relationship as a light source characteristic;
A reference brightness acquisition unit for registration that acquires the reference brightness under illumination conditions during non-defective imaging as the reference brightness for registration;
A light amount control amount calculation unit for calculating the light amount control amount necessary to obtain the registration-time reference brightness on the reference surface based on the light source characteristics;
An illumination controller that controls the light amount of the light source at the time of imaging of the inspection object, according to a calculation value by the light amount control amount calculation unit;
An appearance inspection apparatus comprising:   The registration-time reference brightness acquisition unit acquires the registration-time reference brightness by converting a light amount control amount at the time of imaging the good product into the reference brightness based on the light source characteristics. Item 1. An appearance inspection apparatus according to Item 1. A light source characteristic storage unit for storing the light source characteristic measured by the light source characteristic measurement unit;
The light quantity control amount calculation unit performs the calculation based on the light source characteristic stored in the light source characteristic storage unit, so that the measurement for a plurality of inspection objects is performed for one measurement by the light source characteristic measurement unit. The appearance inspection apparatus according to claim 1 or 2, wherein the calculation is configured to be repeatable.   The appearance inspection apparatus according to claim 1, further comprising a conveyance unit that relatively moves the reference plane instead of the inspection object at an imaging position of the inspection object.   The said light source characteristic measurement part calculates | requires the said light source characteristic based on the image data of several sheets which changed the light quantity of the said light source, and imaged the said reference plane. Visual inspection equipment. In the appearance inspection apparatus for determining the quality of the inspection object based on the comparison of the images obtained by imaging the non-defective product and the inspection object under the illumination condition by the light source,
A light source characteristic measurement unit for obtaining a relationship between a reference brightness that is a brightness of a reference surface when the reference surface that is substituted for the light receiving surface to be inspected is illuminated by the light source and a light amount of the light source, as a light source characteristic;
A reference brightness acquisition unit for registration that acquires the reference brightness under illumination conditions during non-defective imaging as the reference brightness for registration;
Based on the light source characteristics, a light amount calculation unit that calculates the light amount of the light source necessary for obtaining the reference brightness at the reference plane on the reference surface;
An illumination controller that controls the light amount of the light source at the time of imaging of the inspection object, according to a calculation value by the light amount control amount calculation unit;
An appearance inspection apparatus comprising:

Images