Visual inspection device

Abstract

To provide a visual inspection device with which it is possible to accurately evaluate workpiece abnormality on the basis of a high-definition captured image.SOLUTION: A control unit 50 causes a side face 5 of a chip 4 placed on an inspection table 40 to be imaged and a plurality of images I for evaluation to be generated, while changing the focus position of a side face imaging device 32 by a prescribed pitch at a time. The control unit 50 sets different evaluation regions EI1, EI2, EI3 to the image I for evaluation, and selects respective focused images IF1, IF2, IF3 of each evaluation region EI1, EI2, EI3 whose focus degree is highest from the plurality of images I for evaluation. The control unit 50 calculates a correction value for direction of the chip 4 relative to the side face imaging device 32 on the basis of a difference in focus position when each focused image IF1, IF2, IF3 is imaged, and causes an inspection table turning mechanism 41 to correct the direction of the chip 4.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an apparatus for visual inspection of a workpiece. [Background technology]

[0002] In the visual inspection process of optical elements such as laser diodes, it is important to evaluate for abnormalities based on images of the light-emitting surface captured in detail, because the condition of the light-emitting surface of the optical element affects the light irradiation characteristics.

[0003] The main methods of constructing the resonator of a laser diode are the edge-emitting type, in which the resonator is constructed parallel to the semiconductor substrate surface and light is extracted from the cleavage plane, and the surface-emitting type, in which the resonator is constructed perpendicular to the semiconductor substrate surface. Of these, the edge-emitting type laser diode has a light-emitting surface on the side when placed, so that in appearance inspection, it is required to precisely image the side surface, which is the light-emitting surface.

[0004] The visual inspection process for semiconductor devices is often carried out while the chips are being transported after separation. The separated chips are picked up from the dicing sheet using a collet or the like and placed on the inspection table. In this state, cameras installed around the inspection table sequentially capture images of the chips. Image processing technology is applied to the image data generated by the camera to evaluate the chips for abnormalities.

[0005] For example, Patent Document 1 discloses a visual inspection device that images the side surface of a chip element placed on a table. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2021-192030 A Summary of the Invention [Problem to be solved by the invention]

[0007] When imaging the side of a chip placed on an inspection table, the orientation of the chip relative to the camera lens is important. In order to obtain a fine image in which the entire side of the chip is in focus, it is desirable that the optical axis of the camera is perpendicular to the side of the chip. However, since the position and orientation of the chip placed on the inspection table are different each time, the side of the chip is likely to be tilted to the left or right relative to the camera lens. In order to correct this tilt, the chip is usually imaged by a camera separately provided above the chip, and a process is performed to detect the tilt of the side by applying edge recognition or the like to the obtained image. However, depending on damage to the side of the chip or the state of the solder, the edge of the side cannot be accurately recognized by imaging from above, and the tilt of the chip cannot be sufficiently corrected. Depending on the magnitude of this tilt, it is possible to focus only on a part of the left and right areas of the side of the chip, making it difficult to obtain a fine image.

[0008] For example, in a lens with a wide depth of field such as a telecentric lens, the above-mentioned problem is unlikely to occur even if the side of the chip is slightly tilted, but when a lens with a shallow depth of field is used in relation to other imaging conditions, the above-mentioned problem may occur even with a slight tilt of the chip. The invention described in Patent Document 1 does not perform accurate orientation adjustment for each chip element, so it is thought that the above-mentioned problem may occur depending on the lens used.

[0009] The present invention has been made in consideration of the above circumstances, and its object is to provide a visual inspection device that can accurately evaluate abnormalities in a workpiece based on fine captured images. [Means for solving the problem]

[0010] The visual inspection apparatus of the present invention comprises a support unit having a support surface that supports the bottom surface of a workpiece, a side imaging unit that images the side surface of the workpiece and generates an image for evaluation, an orientation adjustment unit that drives the support unit and changes the orientation of the workpiece relative to the side imaging unit, and a control unit that controls the side imaging unit and the orientation adjustment unit. The control unit executes a multifocal imaging process in which the side imaging unit images the side of the workpiece at a plurality of different focus positions to generate a plurality of the evaluation images; a focused image selection process in which the focus degrees of a first evaluation area and a second evaluation area, which are two different areas respectively set at corresponding positions in the plurality of evaluation images, are calculated, and a first focused image having the highest focus degree of the first evaluation area and a second focused image having the highest focus degree of the second evaluation area are selected from the plurality of evaluation images; and a correction process in which the correction value of the orientation of the workpiece relative to the side imaging unit is calculated based on the difference between a first focus position which is the focus position of the side imaging unit when the first focused image is captured and a second focus position which is the focus position of the side imaging unit when the second focused image is captured, and the orientation adjustment unit is caused to correct the orientation of the workpiece based on the correction value.

[0011] In the above-mentioned configuration, the correction value of the orientation of the workpiece is calculated based on the difference between the first focal position, which is the focal position of the side imaging unit when the first focused image with the highest focus level of the first evaluation area is captured among the multiple evaluation images captured at multiple different focus positions, and the second focal position, which is the focal position of the side imaging unit when the second focused image with the highest focus level of the second evaluation area is captured, so that the orientation of the workpiece with respect to the side imaging unit can be accurately corrected. This makes it possible to accurately evaluate abnormalities in the workpiece based on fine captured images captured with little tilt of the workpiece.

[0012] In the above, the expressions "bottom surface" and "side surface" are merely for convenience, and do not necessarily mean that the "bottom surface" is horizontal and the "side surface" is vertical. The orientation of the "bottom surface" or "side surface" of the workpiece may change depending on the orientation in which the support part is installed. In addition, in the above, the "degree of focus" is a value indicating the degree to which the image is in focus when captured, and does not limit the evaluation method. Effect of the Invention

[0013] According to the present invention, it is possible to accurately evaluate abnormalities in a workpiece based on fine captured images. [Brief description of the drawings]

[0014] [Figure 1] 1A and 1B are diagrams showing a mechanism for capturing an image of a chip 4 in a visual inspection apparatus 10 according to an embodiment of the present invention, where (A) is a front view and (B) is a plan view. In (B), the top surface imaging device 31 is omitted. [Diagram 2] FIG. 2 is a functional block diagram showing connections between the control unit 50 and each unit in the visual inspection apparatus 10. As shown in FIG. [Diagram 3] FIG. 3 is a flow chart showing the flow of the visual inspection of the chip 4. [Figure 4] FIG. 4 is a flowchart showing the flow of the multifocal imaging process executed during the visual inspection of the chip 4. [Diagram 5] FIG. 5 is a flowchart showing the flow of the focused image selection process executed during the visual inspection of the chip 4. [Figure 6] FIG. 6 is a flowchart showing the flow of the correction process executed during the visual inspection of the chip 4. [Figure 7] FIG. 7 is a flowchart showing the flow of a combined image generating process executed during the visual inspection of the chip 4. [Figure 8] FIG. 8 is an enlarged view of the periphery of the side surface 5 of the chip 4 in FIG. 1(B). [Figure 9]FIG. 9 is a diagram showing an evaluation image I generated by imaging the side surface 5 of the chip 4. As shown in FIG. [Figure 10] Figure 10 shows focused images IF1, IF2, and IF3 selected from multiple evaluation images I, where (A) is the first focused image IF1, (B) is the second focused image IF2, and (C) is the third focused image IF3. [Figure 11] Figure 11 shows region images IE1, IE2, and IE3 cut out from the focused regions EF1, EF2, and EF3 of each focused image IF1, IF2, and IF3, where (A) is the first region image IE1, (B) is the second region image IE2, and (C) is the third region image IE3. [Figure 12] FIG. 12 is a diagram showing a combined image IC generated from each of the area images IE1, IE2, and IE3. [Figure 13] FIG. 13 is a diagram showing focused images IF1 and IF2 selected from an evaluation image I in a modified example of the present invention, where (A) is the first focused image IF1 and (B) is the second focused image IF2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A first embodiment of the present invention will be described below. Note that the embodiment described below is merely one example of the present invention, and it goes without saying that the embodiment of the present invention can be modified as appropriate without departing from the gist of the present invention. In the following description, when the visual inspection device 10 is installed, the up-down direction 1 is defined along the vertical direction, and the front-rear direction 2 and the left-right direction 3 are defined along the horizontal direction. The up-down direction 1, the front-rear direction 2, and the left-right direction 3 are also perpendicular to each other.

[0016] [Overview and overall configuration of the visual inspection device 10] 1 and 2 captures an image of a chip 4 (corresponding to a "workpiece" in the claims) placed on an inspection table 20 (corresponding to a "support" in the claims), and evaluates the chip 4 for abnormalities based on the generated image. The chip 4 is an optical element, and is generally an edge-emitting laser diode chip.

[0017] The visual inspection device 10 includes an inspection table 20 (FIG. 1) on which the chip 4 is placed, an imaging unit 30 for imaging the chip 4, a driving unit 40 (FIG. 2) for adjusting the positional relationship between the chip 4 and the imaging unit 30 when imaging, and a control unit 50 (FIG. 2) for controlling each unit of the visual inspection device 10. However, the above is only the configuration necessary for solving the problem of the present invention, and the visual inspection device 10 may have various other components. For example, the visual inspection device 10 may include a collet mechanism for picking up and transporting the placed chip 4. Alternatively, the visual inspection device 10 may be integrated with a dicing device for dividing the wafer into chips 4 by a dicing process. However, in the following description, components unrelated to solving the problem of the present invention such as those exemplified here will be omitted. Each component constituting the visual inspection device 10 will be described in more detail below.

[0018] [Examination table 20] The inspection table 20 is a table on which the chip 4 is placed when the chip 4 is imaged, and supports the chip 4 from below. The inspection table 20 has a flat upper surface (corresponding to the "support surface" in the claims) on which the chip 4 is placed, and has a circular, approximately cylindrical shape when viewed from above. Although not shown in the figure, the inspection table 20 is supported from below by an inspection table rotation mechanism 41 (corresponding to the "orientation adjustment unit" in the claims in FIG. 2) of a drive unit 40 (FIG. 2) described later. This allows the inspection table 20 to be selectively rotated clockwise or counterclockwise in a rotation direction D1 (FIG. 1(B)) around a central axis CA (FIG. 1(A) corresponding to the "axis" in the claims).

[0019] [Imaging unit 30] The imaging unit 30 images the chip 4 and generates image data to be used for visual inspection. The imaging unit 30 includes a top imaging device 31 and a side imaging device 32 (corresponding to the "side imaging unit" in the claims). The top imaging device 31 and the side imaging device 32 are industrial cameras incorporating a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor as an imaging element.

[0020] The top surface imaging device 31 is provided above the inspection table 20. The lens of the top surface imaging device 31 faces downward, and during imaging, the lens faces the top surface of the chip 4 to image the top surface of the chip 4 from above.

[0021] The side imaging device 32 images the side surface 5 that forms the light emitting surface of the chip 4. The side imaging device 32 is located on the front side in the front-rear direction 2 with respect to the inspection table 20, and is disposed at a position where the side surface 5 of the chip 4 can be imaged from the lateral direction. The lens of the side imaging device 32 is directed toward the chip side (rear side in the front-rear direction 2), and more precisely, the lens is oriented such that the optical axis OA (FIG. 1) of the side imaging device 32 is aligned along the upper surface of the inspection table 20.

[0022] The top imaging device 31 and the side imaging device 32 are each supported by a camera driving mechanism 43 (FIG. 2) of a driving unit 40 (FIG. 2) described later. This allows the top imaging device 31 and the side imaging device 32 to move along the up-down direction 1, the front-back direction 2, and the left-right direction 3. In addition, the top imaging device 31 and the side imaging device 32 are each electrically connected to a control unit 50 (FIG. 2) described later, and the imaging operation thereof is controlled by the control unit 50.

[0023] [Drive unit 40] The driving unit 40 (FIG. 2) is composed of an examination table rotating mechanism 41 that supports the examination table 20 from below, and a camera driving mechanism 43 that supports the top imaging device 31 and the side imaging device 32. The examination table rotating mechanism 41 is equipped with a motor 42 that can selectively rotate in a forward or reverse direction under the control of the control unit 50. The rotational driving force of the motor 42 is transmitted to the examination table 20 via a drive transmission mechanism (not shown) that is composed of a gear, a pulley, a belt, or the like. As a result, the examination table 20 rotates along the rotational direction D1. For example, the examination table 20 rotates clockwise when receiving the forward rotational driving force of the motor 42, and rotates counterclockwise when receiving the reverse rotational driving force of the motor 42.

[0024] The camera driving mechanism 43 integrally supports the top imaging device 31 and the side imaging device 32. The camera driving mechanism 43 includes a plurality of actuators 44, 45, 46 that operate under the control of the control unit 50. The top imaging device 31 and the side imaging device 32 can selectively move along the up-down direction 1, the front-rear direction 2, and the left-right direction 3 by receiving the driving force of the actuators 44, 45, 46. For example, the top imaging device 31 and the side imaging device 32 move along the up-down direction 1 by receiving the driving force of the actuator 44, the top imaging device 31 and the side imaging device 32 move along the front-rear direction 2 by receiving the driving force of the actuator 45, and the top imaging device 31 and the side imaging device 32 move along the left-right direction 3 by receiving the driving force of the actuator 46. At this time, the movements in each direction may be performed simultaneously. In this embodiment, the top surface imaging device 31 and the side surface imaging device 32 are supported integrally and move together, but a mechanism for moving the top surface imaging device 31 and a mechanism for moving the side surface imaging device 32 may be provided separately, and the top surface imaging device 31 and the side surface imaging device 32 may be configured to move differently.

[0025] Although not shown in the figure, the driving unit 40 may include a rotary encoder that detects the amount of rotation of the examination table 20, a linear encoder that detects the amount of movement of the top imaging device 31 or the side imaging device 32, etc. The control unit 50 refers to signals from these encoders, thereby making it possible to control the amount of rotation of the driving unit 40 and the amount of movement of the top imaging device 31 and the side imaging device 32 with higher accuracy.

[0026] [Control unit 50] The control unit 50 (FIG. 2) is a computer that controls the overall operation of the visual inspection apparatus 10. The control unit 50 includes, as a minimum configuration, a CPU (Central Processing Unit) 51, a main memory 52, an EEPROM (Electrically Erasable Programmable Read-Only Memory) 53 as an auxiliary storage device, and an internal bus 54 for data transmission between them. The control unit 50 also includes an input / output interface and a network interface, but these will not be described here. The EEPROM 53 stores various programs for controlling the operation of the visual inspection apparatus 10. These programs are loaded into the main memory 52 through the internal bus 54 and executed by the CPU 51. Control signals generated as a result are transmitted to each part of the visual inspection apparatus 10 through an external bus 55, respectively, to control the overall operation of the visual inspection apparatus 10.

[0027] The EEPROM 53 stores a driver program for controlling the operation of the drive unit 40 and the imaging unit 30. The EEPROM 53 also stores an image processing program for processing image data generated by the imaging unit 30, and an evaluation program for evaluating abnormalities in the chip 4 based on the image data. The EEPROM 53 also stores programs for executing multi-focal imaging processing, focused image selection processing, correction processing, and combined image generation processing, which will be described later, as well as a program for loading these various programs as subroutines to execute the entire sequence related to the appearance inspection of the chip 4.

[0028] [Details of visual inspection of chip 4] The following describes in detail the visual inspection of the chip 4. Note that the operation of each part of the visual inspection apparatus 10 described below is controlled by the control unit 50 executing various programs stored in the EEPROM 53.

[0029] In the appearance inspection process, first, the chip 4 is placed on the inspection table 20. When appearance inspection is performed during the manufacturing process of the chip 4, the chip 4 that has completed a pre-process such as a dicing process is transported by a transport mechanism such as a collet mechanism, and is placed on the inspection table 20 during the transport process. At this time, it is desirable to place the chip 4 on the upper surface of the inspection table 20 at a position close to the central axis CA.

[0030] FIG. 3 is a flowchart showing the flow of the process of the appearance inspection executed by the control unit 50. The control unit 50 adjusts the positional relationship between the top surface imaging device 31 and the side surface imaging device 32 and the chip 4 in order to image the chip 4 (step S10). First, the control unit 50 refers to the image generated by the top surface imaging device 31 and moves the top surface imaging device 31 in the front-rear direction 2 and the left-right direction 3 so that the top surface imaging device 31 is located at a position where it can image the entire top surface of the chip 4. In this state, the control unit 50 detects the side surface 5 of the chip 4 to be inspected from the image generated by the top surface imaging device 31 by an image processing algorithm such as edge recognition. The control unit 50 rotates the inspection table 20 and adjusts the orientation of the chip 4 so that the side surface of the chip 4 faces the side surface imaging device 32. Next, the control unit 50 refers to the image generated by the side surface imaging device 32 and moves the side surface imaging device 32 in the up-down direction 1 until the optical axis OA of the side surface imaging device 32 passes through the side surface 5. This series of operations may be executed once, but all or part of the operations may be executed repeatedly to adjust the positional relationship between the top imaging device 31 and the side imaging device 32 and the chip 4 with higher accuracy.

[0031] After adjusting the positional relationship between the top surface imaging device 31 and the side surface imaging device 32 and the chip 4, the top surface of the chip 4 is imaged by the top surface imaging device 31 (step S20). The control unit 50 causes the top surface imaging device 31 to adjust the focus so that the focus is on the top surface of the chip 4, and to image the top surface of the chip 4. The captured image generated by the top surface imaging device 31 is transmitted to the control unit 50 via the external bus 55 and stored in the EEPROM 53.

[0032] Next, the control unit 50 executes a multifocal imaging process for imaging the side surface 5 of the chip 4 (step S30). The multifocal imaging process is a process for imaging the side surface 5 of the chip 4 multiple times while changing the focal position of the side surface imaging device 32 by a specified pitch. This focal position is the position of the imaging target surface at which the camera is focused, and is specified by the distance from the lens along the optical axis of the lens.

[0033] 8 shows an example of focus positions when the side image capturing device 32 captures an image of the side surface 5 of the chip 4 by the multifocal imaging process. Here, a total of 10 focus positions P1 to P10 are used. Each of the focus positions P1 to P10 forms a plane perpendicular to the optical axis OA of the side image capturing device 32. Adjacent focus positions are spaced apart by a predetermined pitch, and the focus positions P1 to P10 are set so that the side surface 5 of the chip 4 is located between any of the focus positions P1 to P10.

[0034] For example, the side surface 5 of the chip 4 shown by the solid line in Fig. 8 is inclined with respect to the planes formed by the focal positions P1 to P10. The left end of the side surface 5 of the chip 4 is located closest to the focal position P5, and the right end is located closest to the focal position P8. This means that when the side surface 5 is imaged at the focal position P5, an image best focused on the left end of the side surface 5 is obtained, and when the side surface 5 is imaged at the focal position P8, an image best focused on the right end of the side surface 5 is obtained.

[0035] 8 is parallel to the planes formed by the focal positions P1 to P10, and is located closest to the focal position P6. This means that when the side surface 5 is imaged at the focal position P6, an image in which the entire side surface 5 is most in focus is obtained.

[0036] A flow chart showing the multi-focal imaging process is shown in Fig. 4. The control unit 50 changes the internal parameters of the side image capturing device 32, and sets it so that imaging is performed at the focal position P1 (step S31). In this state, the control unit 50 causes the side image capturing device 32 to capture an image of the side surface 5 of the chip 4 (step S32). The evaluation image I (Fig. 9) generated by the side image capturing device 32 is transmitted to the control unit 50 via the external bus 55 and stored in the EEPROM 53.

[0037] While imaging at all of the focus positions P1 to P10 has not been completed (step S33: NO), the control unit 50 changes the focus position of the side image capturing device 32 by one pitch at a time (step S34) and similarly causes the side image capturing device 32 to capture images of the side surface 5 of the chip 4 at each of the changed focus positions (step S32). When imaging at all of the focus positions P1 to P10 has been completed (step S33: YES), the control unit 50 ends the multifocal imaging process.

[0038] Next, the control unit 50 executes a focused image selection process to select a first focused image, a second focused image, and a third focused image from the evaluation images I (step S40). A flowchart showing the multifocal imaging process is shown in FIG. 5. In the EEPROM 53, a plurality of evaluation images I generated by the side image capturing device 32 by capturing images at each of the focus positions P1 to P10 in the multifocal imaging process are stored. The control unit 50 applies an image processing algorithm such as edge recognition to one of the evaluation images I to detect the four edges of the top, bottom, left, and right of the side surface 5 of the chip 4. Then, a first evaluation area EI1 (FIG. 9) and a second evaluation area EI2 (FIG. 9) are set around the detected left and right edges. Here, the area set around the left edge is the first evaluation area EI1, and the area set around the right edge is the second evaluation area EI2. The control unit 50 also sets a third evaluation area EI3 (FIG. 9) around either the top or bottom edge that has been detected, near the center between the left and right (step S41). Note that in this embodiment, the description will be given assuming that the third evaluation area EI3 is set around the top edge of the side surface 5 of the chip 4.

[0039] The control unit 50 calculates the degree of focus of each of the first evaluation area EI1, the second evaluation area EI2, and the third evaluation area EI3 of the evaluation image I. The degree of focus can be calculated by any method. For example, the contrast value of each evaluation area EI1, EI2, and EI3 may be the degree of focus, or the magnitude of the high-frequency component in the spatial frequency may be the degree of focus. In addition, the control unit 50 sets the first evaluation area EI1, the second evaluation area EI2, and the third evaluation area EI3 of the same size and coordinate position as the evaluation areas EI1, EI2, and EI3 set in the evaluation image I for all other evaluation images I, and calculates the degree of focus for each of them (step S42).

[0040] The control unit 50 compares the focus degree of the first evaluation area EI1 among all the evaluation images I, and selects the evaluation image I with the highest focus degree of the first evaluation area EI1 as the first focused image IF1 (FIG. 10(A)). Similarly, the control unit 50 compares the focus degree of the second evaluation area EI2 among all the evaluation images I, and selects the evaluation image I with the highest focus degree of the second evaluation area EI2 as the second focused image IF2 (FIG. 10(B)). Similarly, the control unit 50 compares the focus degree of the third evaluation area EI3 among all the evaluation images I, and selects the evaluation image I with the highest focus degree of the third evaluation area EI3 as the third focused image IF3 (FIG. 10(C)) (step S43).

[0041] Next, the control unit 50 determines the degree of inclination of the chip 4 with respect to the side image capturing device 32 based on information on which of the focus positions P1 to P10 the evaluation images I captured at are selected as the first focused image IF1, the second focused image, and the third focused image IF3 (step S50). In order to obtain an ideal captured image in which the entire side surface 5 of the chip 4 in the left-right direction 2 is in focus, it is desirable that the side surface 5 of the chip 4 is perpendicular to the optical axis OA of the side image capturing device 32, as shown by the dashed line in FIG. 8. In this state, the same evaluation image I is selected as the first focused image IF1, the second focused image IF2, and the third focused image IF3. For example, in the state shown by the dashed line in FIG. 8, the side surface 5 is closest to the focus position P6, so that the evaluation images I captured at the focus position P6 are selected as the first focused image IF1, the second focused image IF2, and the third focused image IF3.

[0042] On the other hand, as shown by the solid line in FIG. 8, when the side surface 5 of the chip 4 is tilted from the above-mentioned ideal state, different evaluation images I are selected as the first focused image IF1, the second focused image IF2, and the third focused image IF3. For example, in the state shown by the solid line in FIG. 8, the evaluation image I captured at the focus position P5 is selected as the first focused image IF1, and the evaluation image I captured at the focus position P8 is selected as the second focused image IF2. This is because the left end of the side surface 5 in which the first evaluation area EI1 is set is closest to the focus position P5, and the right end of the side surface 5 in which the second evaluation area EI2 is set is closest to the focus position P8. In addition, since the center of the side surface 5 in which the third evaluation area EI3 is set is located between the focus positions P6 and P7, the evaluation image I captured at the focus positions P6 or P7 is selected as the third focused image IF3.

[0043] That is, the greater the left / right inclination of the chip 4 from the ideal state in which the side surface 5 of the chip 4 is perpendicular to the optical axis OA of the side imaging device 32, the greater the difference in focus position when each of the focused images IF1, IF2, and IF3 is captured. Hereinafter, the focus position when the first focused image IF1 is captured will be referred to as the first focus position, the focus position when the second focused image IF2 is captured will be referred to as the second focus position, and the focus position when the third focused image IF3 is captured will be referred to as the third focus position.

[0044] The control unit 50 judges whether the tilt of the tip 4 is within the allowable range based on the difference (how many pitches) between the focus positions. The user can set an appropriate value for this allowable range in advance and store it in the EEPROM 53. For example, the setting may be made so as to allow only the case where the first to third focus positions are the same, that is, the same evaluation image I is selected as the first focused image IF1, the second focused image IF2, and the third focused image IF3. Alternatively, in a situation where the pitch between adjacent focus positions is set small, the setting may be made so as to allow a difference of up to a predetermined number of pitches between the first to third focus positions. Here, the allowable value of the difference between the first focus position and the second focus position corresponds to the "threshold value" in the claims.

[0045] If the inclination of the chip 4 is not within the acceptable range (step S50: NO) and the correction of the orientation of the chip 4 has not yet been performed the specified maximum number of times (step S60: NO), the control unit 50 executes a correction process to correct the orientation of the chip 4 (step S70).

[0046] A flow chart showing the correction process is shown in FIG. 6. The control unit 50 acquires various information necessary for correcting the orientation of the chip 4 (inspection table 20) in addition to the difference between the first to third focal positions (step S71). Examples of this information include, for example, the dimension of the chip 4 in the left-right direction 3 and the positional relationship between the central axis CA of the inspection table 20 and the chip 4. These pieces of information can be acquired from an image of the chip 4 already captured during the process. Alternatively, if the chip 4 to be used is known in advance, information specific to the chip 4 may be stored in the EEPROM 53 by the user in advance. The control unit 50 calculates a correction value for the orientation of the chip 4 (inspection table 20) based on these pieces of information (step S72). The correction value calculated here is information regarding how much the inspection table 20 is rotated in either the clockwise or counterclockwise direction in the rotation direction D1. However, it is not essential that these pieces of information are used to calculate the correction value, and only the difference between the first to third focal positions may be used to calculate the correction value for the orientation of the chip 4 (inspection table 20). The control unit 50 controls the examination table rotating mechanism 41 based on the calculated correction value to rotate the examination table 20 in a required direction by a required angle (step S73), and then ends the correction process.

[0047] After the correction process is performed, the control unit 50 performs the multifocal imaging process and the focused image selection process again (steps S30 and S40). That is, the control unit 50 causes the side image capturing device 32 to capture a plurality of evaluation images I again in the same manner as described above, and selects the first focused image IF1, the second focused image IF2, and the third focused image IF3 from among them again. Next, the control unit 50 determines the degree of inclination of the chip 4 with respect to the side image capturing device 32 from the difference between the first to third focus positions (step S50). If the inclination of the chip 4 is not within the allowable range (step S50: NO) and the correction of the orientation of the chip 4 has not yet been performed the upper limit number of times (step S60: NO), the control unit 50 performs the correction process to correct the orientation of the chip 4 again (step S70), and thereafter, the control unit 50 repeatedly performs the processes from step S30 to step S70.

[0048] On the other hand, if it is determined in the processing of step S50 that the tilt of the chip 4 is within the allowable range (step S50: YES), the control unit 50 selects an evaluation image I to be used for evaluating the side of the chip 4 based on the first to third focus positions.

[0049] For example, when the first focused image IF1, the second focused image IF2, and the third focused image IF3 are the same image, as in the chip 4 shown by the dashed line in FIG. 8, the control unit 50 determines to use the focused image for evaluation of the side surface of the chip 4. On the other hand, when the first focused image IF1, the second focused image IF2, and the third focused image IF3 are different images, as in the chip 4 shown by the solid line in FIG. 8, the control unit 50 determines to use one of the three focused images IF1, IF2, and IF3 for evaluation of the side surface of the chip 4. In particular, it is desirable to use the third focused image IF3, which is an image with a high degree of focus near the center of the side surface 5, for evaluation of the side surface of the chip 4. For example, in the chip 4 shown by the solid line in FIG. 8, it is desirable to use the evaluation image I (third focused image IF3) captured at the focus position P6 or the focus position P7 for evaluation of the side surface of the chip 4.

[0050] The control unit 50 evaluates the side surface of the chip 4 for abnormalities based on the selected evaluation image I. At the same time, the control unit 50 evaluates the upper surface of the chip 4 for abnormalities based on the captured image of the upper surface of the chip 4 generated in step S20 (step S90). Examples of such abnormalities include foreign matter attached to the chip 4 and chipping of the chip 4. The control unit 50 evaluates the abnormalities of the chip 4 using an evaluation algorithm that uses, for example, a rule base or deep learning, and stores the evaluation result in the EEPROM 53. The evaluation result may be merely a determination of whether or not the chip 4 is acceptable as a product, or more detailed evaluation items may be created.

[0051] Furthermore, the control unit 50 may output the evaluation result of the abnormality of the chip 4 to the outside. For example, the control unit 50 may display the evaluation result on a display screen provided in the appearance inspection device 10, or may transmit the evaluation result to a computer connected to the appearance inspection device 10 via a communication network and display the evaluation result on a display screen of the computer. Alternatively, a configuration may be adopted in which chips 4 that are acceptable as products are automatically separated from chips 4 that are not acceptable as products. After completing the above processing, the control unit 50 ends the appearance inspection processing.

[0052] The process for when the inclination of the chip 4 is determined to be within the allowable range in any of the judgments in step S50 (step S50: YES) is as described above. On the other hand, the process for when the inclination of the chip 4 is never determined to be within the allowable range in multiple judgments in step S50 and the upper limit number of corrections to the orientation of the chip 4 is reached (step S60: YES) is described below. This situation can occur, for example, when the side surface 5 of the chip 4 is not flat, such as when there is a chip on the side surface 5.

[0053] If the correction of the orientation of the chip 4 has already reached the specified upper limit number of times (step S60: YES), the control unit 50 executes a combined image generation process (step S80) without further correcting the orientation of the chip 4. The combined image generation process is a process that uses only areas with high focus levels in each of the multiple evaluation images I to generate a combined image IC (FIG. 12) to be used in the evaluation of abnormalities (step S90).

[0054] A flowchart showing the combined image generation process is shown in FIG. 7. The control unit 50 sets a first focused area EF1 (FIG. 10(A)) around the first evaluation area EI1 in the first focused image IF1, sets a second focused area EF2 (FIG. 10(B)) around the second evaluation area EI2 in the second focused image IF2, and sets a third focused area EF3 (FIG. 10(C)) around the third evaluation area EI3 in the third focused image IF3 (step S81). The first focused area EF1 is an area that includes the first evaluation area EI1 as a part thereof, and is an area that covers about one third of the left side in the left-right direction 3 of the side surface 5 of the chip 4. The second focused area EF2 is an area that includes the second evaluation area EI2 as a part thereof, and is an area that covers about one third of the right side in the left-right direction 3 of the side surface 5 of the chip 4. The third focusing area EF3 is an area that includes the third evaluation area EI3 as a part thereof, and covers about one-third of the center of the side surface 5 of the chip 4 in the left-right direction 3. The first focusing area EF1, the second focusing area EF2, and the third focusing area EF3 are set so that their vertical sizes and vertical coordinate positions are the same. In addition, the rightmost area of ​​the first focusing area EF1 partially overlaps with the leftmost area of ​​the third focusing area EF3, and the leftmost area of ​​the second focusing area EF2 partially overlaps with the rightmost area of ​​the third focusing area EF3.

[0055] To set the first focusing area EF1, the second focusing area EF2, and the third focusing area EF3, the control unit 50 acquires the position and range of the side surface 5 of the chip 4 in each focused image IF1, IF2, IF3 by a predetermined image processing algorithm. Alternatively, if the size of the chip 4 is known in advance, the control unit 50 may set the first to third focusing areas EF1, EF2, EF3 as areas obtained by expanding the first to third evaluation areas EI1, EI2, EI3 in the vertical and horizontal directions by a specified number of pixels. The control unit 50 stores in the main memory 52 the image generated by cropping out the first focusing region EF1 of the first focusing image IF1 as a first region image IE1 (Figure 11(A)), stores in the main memory 52 the image generated by cropping out the second focusing region EF2 of the second focusing image IF2 as a second region image IE2 (Figure 11(B)), and stores in the main memory 52 the image generated by cropping out the third focusing region EF3 of the third focusing image IF3 as a third region image IE3 (Figure 11(C)) (step S82).

[0056] The control unit 50 horizontally connects the first region image IE1, the second region image IE2, and the third region image IE3 to generate a combined image IC (FIG. 12) (step S83). The relative positions of the three region images IE1, IE2, and IE3 at this time correspond to the relative positions of the first focused region EF1, the second focused region EF2, and the third focused region EF3 set in each evaluation image I. That is, the first region image IE1 is positioned at the left end, the second region image IE2 is positioned at the right end, and the third region image IE3 is positioned in the center. When the relative positions of the three region images IE1, IE2, and IE3 are determined in this manner, the right end region of the first region image IE1 partially overlaps with the left end region of the third region image IE3, and the left end region of the second region image IE2 partially overlaps with the right end region of the third region image IE3. The brightness value of the pixel in the overlapping region EO may be the brightness value of one of the two overlapping region images IE1, IE2, IE3. Alternatively, the average value of the brightness values ​​of the corresponding pixels in the two overlapping region images IE1, IE2, IE3 may be used. The control unit 50 stores the generated combined image IC in the EEPROM 53.

[0057] The control unit 50 evaluates the side surface of the chip 4 for abnormalities based on the generated combined image IC. At the same time, the control unit 50 evaluates the top surface of the chip 4 for abnormalities based on the captured image of the top surface of the chip 4 generated in step S20 (step S90). The subsequent processing is the same as described above, and will not be repeated.

[0058] [Effects of this embodiment] In the appearance inspection apparatus 10 according to this embodiment, a correction value for the orientation of the chip 4 (inspection table 20) is calculated based on the difference between the first to third focal positions (step S70), making it possible to accurately correct the orientation of the chip 4 (inspection table 20) with respect to the side imaging device 32. This makes it possible to accurately evaluate an abnormality in the chip 4 based on a fine evaluation image I captured with the chip 4 at a small tilt.

[0059] Furthermore, if the inclination of the chip 4 is not within the acceptable range (step S50: NO), correction of the orientation of the chip 4 (inspection table 20) is repeatedly performed, so that even if a single orientation correction does not bring the inclination of the chip 4 within the acceptable range, it is possible to prevent the evaluation image I captured in that state from being used to evaluate an abnormality in the chip 4.

[0060] Furthermore, when the correction of the orientation of the chip 4 reaches the regulated upper limit number of times (step S60: YES), the control unit 50 executes the combined image generation process without further correcting the orientation of the chip 4 (step S80), thereby preventing the correction of the orientation of the chip 4 (inspection table 20) from being executed endlessly. Even in this case, it is possible to accurately evaluate the abnormality of the chip 4 based on the combined image IC generated from the focus areas EF1, EF2, EF3 having high focusing degrees in each of the multiple evaluation images I.

[0061] Furthermore, since each evaluation area EI1, EI2, EI3 is set to include the edge of the side surface 5 of the chip 4, it is possible to accurately calculate the degree of focus even if the side surface 5 of the chip 4 is a featureless surface of uniform color.

[0062] [Modification of this embodiment] In the above-described embodiment, the adjacent focus positions P1 to P10 are spaced apart by a predetermined pitch, but the pitch may be different for each focus position. For example, the pitch may be set finer around the focus position where the side surface 5 of the chip 4 is likely to be located.

[0063] In addition, in the above-described embodiment, each evaluation area EI1, EI2, EI3 was set to include the edge of the side surface 5 of the chip 4, but if there is a characteristic portion on the side surface 5 of the chip 4 that enables accurate calculation of the focus degree, that characteristic portion may be set in each evaluation area EI1, EI2, EI3.

[0064] In the above-described embodiment, if the inclination of the chip 4 is not within the allowable range, the correction of the orientation of the chip 4 (inspection table 20) is repeatedly performed until the number of times of correction of the orientation of the chip 4 reaches a specified upper limit, but this correction may be performed only once. In other words, the control unit 50 may perform the correction of the orientation of the chip 4 (inspection table 20) only once, and if the inclination of the chip 4 is still not within the allowable range, the control unit 50 may perform the combined image generation process.

[0065] In addition, in the above-described embodiment, a combined image IC is generated from the focus areas EF1, EF2, and EF3 of each focused image IF1, IF2, and IF3 in the combined image generation process. However, the control unit 50 may evaluate abnormalities in the side surface 5 of the chip 4 by referring to the focus areas EF1, EF2, and EF3 of each focused image IF1, IF2, and IF3 without executing the combined image generation process.

[0066] In addition, in the above-described embodiment, the focal position of the side imaging device 32 is changed sequentially from focal position P1 to focal position P10, and the side surface 5 of the chip 4 is imaged at each focal position. However, the imaging order at each focal position may be different from this, and may be, for example, the reverse order.

[0067] In the above embodiment, an example in which only one side surface 5 of the chip 4 is evaluated has been shown, but the same process may be repeatedly performed for the other side surfaces 5.

[0068] In the above-described embodiment, three evaluation areas EI1, EI2, EI3 and focus areas EF1, EF2, EF3 are set in the horizontal direction on the evaluation image I, but the evaluation areas EI1, EI2, EI3 and focus areas EF1, EF2, EF3 may be fewer or more than this. For example, in a situation where the tolerance for tilt of the chip 4 is large in relation to the width (dimension in the left-right direction 3) of the side surface 5 of the chip 4 and the depth of field of the side image capturing device 32, only two evaluation areas and focus areas may be set on the left and right. Conversely, in a situation where the tolerance for tilt of the chip 4 is small, four or more evaluation areas and focus areas may be set.

[0069] For example, when only two evaluation areas and a focused area are set in the evaluation image I, as shown in FIG. 13, in the focused image selection process (step S40), the first evaluation area EI1 and the second evaluation area EI2 are set in the same manner as in the above-mentioned embodiment, but the third evaluation area is not set. Then, the first focused image IF1 (FIG. 13(A)) and the second focused image IF2 (FIG. 13(B)) in which the focus degree of each evaluation area EI1, EI2 is the highest are selected. The inclination of the chip 4 is determined (step S50) based on the difference between the first focus position and the second focus position. In the combined image generation process (step S80), the first focused area EF1 (FIG. 13(A)) and the second focused area EF2 (FIG. 13(B)) are set wider inward than those in the above-mentioned embodiment, and are partially overlapped around the center of the evaluation image I (step S81). The combined image is generated by connecting the first focused region EF1 of the first focused image IF1 and the second focused region EF2 of the second focused image IF2 side by side (step S82). [Explanation of symbols]

[0070] 4. Chip (work) 5. Side 10. Visual inspection equipment 20 Inspection table (support part) CA...Central axis line (axis line) 32 Side imaging device (side imaging section) 41 Examination table rotation mechanism (orientation adjustment unit) 50 Control section I...Evaluation image EI1: First evaluation area EI2: Second evaluation area IF1: First focused image IF2: Second focused image EF1...1st focusing area EF2...Second focusing area IC ···Combined Image P1~P10: Focus position

Claims

1. A support portion having a support surface that supports a bottom surface of the workpiece; A side image capturing unit that captures an image of a side surface of the workpiece and generates an evaluation image; an orientation adjustment unit that drives the support unit to change the orientation of the workpiece with respect to the side imaging unit; A control unit that controls the side imaging unit and the orientation adjustment unit, The control unit is A multi-focus imaging process in which the side image capturing unit captures images of the side surface of the workpiece at a plurality of different focus positions to generate a plurality of evaluation images; a focused image selection process for calculating the focus degrees of a first evaluation area and a second evaluation area, which are two different areas respectively set at corresponding positions in the plurality of evaluation images, and selecting, from the plurality of evaluation images, a first focused image having the highest focus degree of the first evaluation area and a second focused image having the highest focus degree of the second evaluation area; a correction process for calculating a correction value for the orientation of the workpiece relative to the side imaging unit based on the difference between a first focal position, which is the focal position of the side imaging unit when the first focused image is captured, and a second focal position, which is the focal position of the side imaging unit when the second focused image is captured, and causing the orientation adjustment unit to correct the orientation of the workpiece based on the correction value.

2. The visual inspection apparatus according to claim 1 , wherein the first evaluation area and the second evaluation area are spaced apart in a direction along the support surface.

3. The visual inspection device according to claim 1 , wherein the orientation adjustment unit is capable of rotating the support unit about an axis perpendicular to the indication surface.

4. 2. The visual inspection device according to claim 1, wherein in the multi-focus imaging process, the control unit causes the side image capturing unit to capture images of the side surface of the workpiece by changing a focal position of the side image capturing unit by a predetermined pitch.

5. The appearance inspection device of claim 1 , wherein in the focused image selection process, the control unit sets the first evaluation area or the second evaluation area based on the position or range of the side surface of the workpiece in the evaluation image.

6. The appearance inspection device of claim 5 , wherein in the focused image selection process, the control unit sets an area including an outer edge of the side surface of the work in the evaluation image as the first evaluation area or the second evaluation area.

7. The control unit selects the evaluation image to be used for evaluating the work based on the first focus position or the second focus position without performing the correction process, with the necessary condition that the same evaluation image has been selected as the first focus image and the second focus image in the focus image selection process, or that the difference between the first focus position and the second focus position is smaller than a threshold value.

8. The control unit executes the multifocal imaging process and the focused image selection process again after executing the correction process, and decides to use both a first focused area which is a peripheral area of ​​the first evaluation area in the first focused image and a second focused area which is a peripheral area of ​​the second evaluation area in the second focused image for evaluating the work, with the necessary condition that the difference between the first focus position of the first focused image selected in the focused image selection process again and the second focus position of the second focused image selected in the focused image selection process again being greater than a threshold value.

9. The visual inspection apparatus of claim 8, wherein the control unit generates a combined image representing a side of the workpiece based on the first focused area in the first focused image and the second focused area in the second focused image that have been determined to be used to evaluate the workpiece.

Images