JP2006084445A - Image acquisition device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire accurately an image of a prescribed domain on a moving object by using a light emitting diode. <P>SOLUTION: This image acquisition device 1 is equipped with a conveyor 2 for moving the object 9 continuously, and a head part 3 provided over the conveyor 2. The head part 3 has the LED 31 for emitting flash light, a microscope 32 guiding the flash light to the object 9 and entered by light from the object 9, and an imaging device 33 for converting an object 9 image formed with a prescribed magnification by the microscope 32 into an electric signal. In the image acquisition device 1, a current exceeding an allowable current at the continuous lighting time is inputted into the LED 31, and flash light is irradiated to the object 9 moved by the conveyor 2, and the image of an inspection domain on the object 9 is acquired. Hereby, the image of the inspection domain on the moving object 9 can be acquired accurately by using the LED 31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image acquisition device that acquires an image of a predetermined area on an object.

  Conventionally, a pattern on a substrate is inspected by acquiring an image of a predetermined inspection area on a semiconductor substrate or a glass substrate (hereinafter referred to as “substrate”). In recent years, there has been known an image acquisition device that acquires an image of an inspection region on a moving substrate using flash light from a strobe light source (see, for example, Patent Documents 1 and 2). In such an image acquisition apparatus, a xenon lamp is generally used as a strobe light source.

In Patent Document 3, in a digital camera using a plurality of light emitting diodes (LEDs) as a strobe light source, a desired lighting state can be obtained without burdening each LED by sequentially lighting the plurality of LEDs within a predetermined time. A technique for realizing the above is disclosed.
JP-A-10-123016 JP 11-326233 A JP 2001-215579 A

  By the way, it is known that the LED is easier to control and has a stable light intensity than the xenon lamp. When using an LED as a strobe light source instead of a xenon lamp in the image acquisition device described above, the amount of light required for imaging cannot be obtained with the flash light from the LED obtained by supplying the rated current, and the image is accurate. Can't get well.

  The present invention has been made in view of the above problems, and an object of the present invention is to accurately acquire an image of a predetermined area on a moving object using a light emitting diode.

  The invention according to claim 1 is an image acquisition device that acquires an image of a predetermined area on an object, and includes an imaging device, a moving mechanism that moves the object relative to the imaging device, A light-emitting diode that irradiates flash light toward an object when a current exceeding an allowable current at the time of lighting is input, and guides light from the object derived from the flash light to the imaging device. An optical system that forms an image of a predetermined area on the object, and a control unit that controls light emission of the light emitting diode and imaging by the imaging device.

  A second aspect of the present invention is the image acquisition device according to the first aspect, wherein a current input to the light emitting diode is five times or more of the allowable current.

  A third aspect of the present invention is the image acquisition device according to the first or second aspect, wherein the pulse width of the flash light is 1 millisecond or less.

  A fourth aspect of the present invention is the image acquisition device according to any one of the first to third aspects, wherein a cycle in which the light emitting diode emits the flash light is 1/300 seconds or less.

  A fifth aspect of the present invention is the image acquisition device according to any one of the first to fourth aspects, wherein the control unit changes a pulse width of the flash light.

  A sixth aspect of the present invention is the image acquisition device according to the fifth aspect, wherein the control unit determines the pulse width of the flash light based on a relative moving speed of an object with respect to the imaging device. change.

  A seventh aspect of the present invention is the image acquisition device according to the sixth aspect, wherein the control unit changes the amount of the flash light in accordance with an object.

  The invention according to an eighth aspect is the image acquisition device according to the fifth aspect, wherein the magnification of the optical system is variable, and the controller is configured to control the flash light based on the magnification of the optical system. The pulse width is changed.

  According to the first to eighth aspects of the present invention, it is possible to accurately acquire an image of a predetermined area on the object that moves relative to the imaging device using the light emitting diode.

  In the invention of claim 4, an image of a predetermined region can be acquired in a short cycle. In the invention of claim 5, the pulse width can be easily changed by using a light emitting diode.

  In the invention of claim 6, an image can be acquired at a desired resolution while matching the relative moving speed. In the invention of claim 8, an image can be acquired at a desired resolution while matching the imaging magnification. can do.

  FIG. 1 is a diagram showing a configuration of an image acquisition apparatus 1 according to an embodiment of the present invention. The image acquisition device 1 is for acquiring an image of a predetermined area on an object such as a printed matter such as a banknote, an industrial part such as a semiconductor chip, or various substrates such as a semiconductor substrate or a glass substrate, The acquired image is used for inspection and processing (for example, bonding of a semiconductor chip on a printed wiring board) for the object.

  The image acquisition device 1 is connected to each component of the conveyor 2 that continuously moves the object 9 in the Y direction in FIG. 1, the head unit 3 provided above the conveyor 2, and the image acquisition device 1. The control unit 4 is provided. The conveyor 2 has a plurality of shafts 21 each facing in the X direction arranged in the Y direction at predetermined intervals. A roller 22 is attached to each shaft 21, and an annular belt 23 (only a part of the belt 23 is shown in FIG. 1) is provided so as to contact the plurality of rollers 22. A part of the plurality of shafts 21 is connected to the motor 24 to rotate, and the object 9 placed on the belt 23 continuously moves in the (+ Y) direction according to the rotation speed of the motor 24. An encoder 25 is attached to the rotating shaft of the motor 24, and the output of the encoder 25 is output to the control unit 4.

  The head unit 3 includes a light emitting diode 31 that emits flash light (hereinafter referred to as “LED 31”), and the flash light from the LED 31 is folded back by a half mirror 321 included in a microscope 32 that is an optical system. Guided up. The reflected light of the flash light from the object 9 is captured by the microscope 32, and an image of the object 9 is formed on the imaging device 33. The imaging device 33 has a plurality of light receiving elements arranged two-dimensionally, and image data of the object 9 is output from the imaging device 33 to the control unit 4. The microscope 32 has a lens group (not shown), and the magnification of the microscope 32 is variable. At a predetermined magnification, the numerical aperture (NA) on the object 9 side of the microscope 32 is, for example, 0.2, and the numerical aperture on the imaging device 33 side is 0.02.

  Next, an operation in which the image acquisition device 1 acquires an image of a predetermined area on the object 9 will be described. In the following description, a plurality of areas to be inspected (hereinafter referred to as “inspection areas”) are periodically set on the object 9, and an image of each inspection area is acquired at a constant magnification. . The positions of the plurality of inspection areas on the object 9 are stored in advance by the control unit 4.

  When acquiring an image of the inspection area, first, the object 9 is placed on the (−Y) side on the driven conveyor 2 and starts moving continuously in the (+ Y) direction. Then, the output from the encoder 25 is output to the control unit 4 so that the moving speed of the object 9 relative to the head unit 3 is detected. In the present embodiment, for example, the object 9 moves continuously at a constant speed of 100 millimeters (mm) per second. A sensor 26 that detects the passage of the object 9 is attached to the (−Y) side of the head unit 3 on the transport path of the object 9, and the control unit 4 uses the output from the sensor 26 to detect the object 9. Is determined. Thereby, the control unit 4 obtains an accurate time when each inspection region on the object 9 reaches the imaging position of the head unit 3.

  Subsequently, the object 9 reaches below the head unit 3, and the (+ Y) side inspection area (hereinafter referred to as “first inspection area”) on the object 9 reaches the imaging position by the head unit 3. When approaching, the electronic shutter of the imaging device 33 is turned on (that is, charge accumulation at each light receiving element of the imaging device 33 is started). When the first inspection region on the object 9 reaches the imaging position of the head unit 3, flash light having a pulse width of 5 microseconds (μ seconds) is emitted from the LED 31 toward the object 9. In the present embodiment, the pulse width of the flash light is determined in advance.

  At this time, the intensity of the flash light depends on the current supplied to the LED 31, and the supplied current is, for example, 1 ampere (A) larger than the allowable current (for example, rated current) when the LED 31 is continuously lit. It is determined according to the pulse width so that the integrated light amount of the flash light applied to the first inspection region on the object 9 becomes a predetermined amount. Preferably, the current input to the LED 31 is at least five times the allowable current during continuous lighting. The reflected light from the object 9 of the flash light is guided to the imaging device 33 by the microscope 32, and an image of the first inspection region on the object 9 is formed on the imaging device 33 at a predetermined magnification. After the flash light irradiation, the electronic shutter of the imaging device 33 is turned off, and an image of the first inspection area is acquired. In the following description, the term “flash light” simply means high-intensity flash light that is emitted when a current determined in accordance with the pulse width (more than the allowable current) is supplied to the LED 31. To do.

  Here, as described above, the object 9 moves at 100 mm per second, and the object 9 moves by 0.5 μm (μm) while being irradiated with flash light. In an image, a blur of 0.5 μm occurs. In other words, the image acquisition device 1 can acquire an image having a length of one side (hereinafter referred to as “resolution”) of a square area on the object 9 corresponding to one pixel of 0.5 μm or more. Actually, depending on the magnification of the microscope 32, an image having a resolution of 0.5 μm or a coarser resolution is acquired. In the following description, the minimum value of the resolution of an image that can be acquired is referred to as limit resolution.

  When the image of the first inspection region is acquired, the image of the second inspection region that is 200 μm away from the first inspection region on the (−Y) side is acquired. Specifically, when the second inspection area approaches the imaging position of the head unit 3, the electronic shutter of the imaging device 33 is turned on. Then, at the same time when the second inspection area reaches the imaging position by the head unit 3, flash light having a pulse width of 5 μs is emitted from the LED 31 and an image of the second inspection area is acquired. At this time, the flash light irradiation to the second inspection region is performed after 1/500 second has elapsed since the last flash light irradiation. Subsequently, the flash light is further irradiated after 1/500 second from the irradiation of the flash light to the second inspection region, and an image of the third inspection region separated by 200 μm from the second inspection region to the (−Y) side is acquired. The That is, in the image acquisition device 1, flash light is emitted from the LED 31 at a cycle of 1/500 seconds, and an image of each inspection region formed at a cycle of 200 μm on the object 9 is acquired. When the images of all the inspection areas on the object 9 are acquired, the image acquisition operation ends.

  As described above, in the image acquisition device 1 of FIG. 1, flash light having a pulse width of 5 μs is emitted from the LED 31 to the object 9 that is moved by the conveyor 2, and is synchronized with the light emission of the LED 31 by the imaging device 33. Imaging is controlled and an image of the inspection region on the object 9 is acquired. Here, in a general light emitting diode, when flash light is emitted for 5 μsec at an allowable current during continuous lighting, the amount of light irradiated onto the object 9 is small, and thus the light receiving of the imaging device 33 is received. Sufficient charges are not accumulated in the element, and an image of the inspection region on the object 9 cannot be acquired appropriately. On the other hand, the LED 31 in the image acquisition device 1 receives a current exceeding the allowable current during continuous lighting, so that the light quantity necessary for imaging is applied to the object 9 even for a short time of 5 μsec. The Thereby, the image of the inspection area on the object 9 that moves relative to the imaging device 33 using the LED 31 can be obtained with high accuracy.

  In the above operation example, the case where flash light having a pulse width of 5 μs is emitted has been described, but in the LED 31, the emission of flash light having a pulse width of 10 μs or less, which is possible using a general xenon lamp, is similarly performed. Can be realized. In such a case, since the light emission time is extremely short, it has been confirmed that the temperature of the LED 31 does not rise to a temperature that leads to breakage (for example, 135 degrees). Therefore, in a general light emitting diode, by providing a heat sink, damage due to heat is suppressed and a certain life is ensured. However, the heat sink can be omitted in the LED 31 of the image acquisition device 1. In addition, when a xenon lamp that emits flash light having a pulse width of 10 μs is used, an image with a resolution of 0.5 μm to 100 μm is mainly acquired, but even when the LED 31 is used instead of the xenon lamp, An image with a resolution in the same range (limit resolution) can be acquired. In this case, the object 9 moves with respect to the imaging device 33 at a moving speed of 50 mm or more and 10 m or less per second.

  In general, in a xenon lamp, it is limited to emit flash light at a period of 1/300 seconds. In the above operation example, the case of emitting flash light at a period of 1/500 seconds has been described. As described above, the LED 31 can emit flash light even with a period of 1/300 seconds or less. As a result, the image acquisition apparatus 1 can acquire an image of the inspection region with a shorter cycle than when a xenon lamp is used. Actually, the flash light can be emitted even with a period of 1/1000 second or less.

  Next, another example of the image acquisition operation by the image acquisition device 1 will be described. In the image acquisition apparatus 1 in this operation example, the images of the inspection region are acquired with different limit resolutions for the plurality of different types of objects 9. Specifically, one type of object (hereinafter referred to as “first object”) 9 is moved at a constant speed by the conveyor 2, and is matched with the limit resolution set for the first object 9. The magnification of the microscope 32 is changed by the control unit 4. Then, the pulse width of the flash light from the LED 31 is determined based on the magnification of the microscope 32 (and the moving speed of the object 9). When the inspection area on the first object 9 reaches the imaging position of the head unit 3, flash light is emitted with the determined pulse width, and the limit where the image of the inspection area on the first object 9 is set Obtained at resolution.

  Subsequently, another type of object 9 (hereinafter referred to as “second object”) 9 moves at the same speed by the conveyor 2, and the first object 9 set for the second object 9 and The magnification of the microscope 32 is changed according to different limit resolutions. In the control unit 4, the pulse width of the flash light from the LED 31 is determined based on the magnification of the microscope 32. For example, when the limit resolution for the second object 9 is 1.5 times the limit resolution for the first object 9 (that is, 1.5 times coarser), it is compared with the condition for the first object 9. Thus, the magnification of the microscope 32 is 1 / (1.5) times and the pulse width of the flash light is 1.5 times. When the inspection area on the second object 9 reaches the imaging position, flash light is emitted with the determined pulse width, and the image of the inspection area on the second object 9 is set to the set limit resolution. Is obtained.

  As described above, in the image acquisition device 1 in this operation example, the control unit 4 changes the pulse width of the flash light based on the magnification of the microscope 32. Here, when a xenon lamp is used, it is necessary to provide a complicated circuit in order to change the pulse width of the flash light. However, the image acquisition device 1 can easily change the pulse width by using a light emitting diode. In addition, it is possible to obtain an image with a desired resolution while adjusting the imaging magnification.

  Next, still another example of the image acquisition operation by the image acquisition device 1 will be described. In the image acquisition apparatus 1 in this operation example, an image of an inspection region is acquired while a plurality of different types of objects 9 are moved by the conveyor 2 at different speeds in accordance with, for example, processing performed on the conveyor 2. Is done. Note that the magnification of the microscope 32 and the resolution of the acquired image of the inspection region are fixed.

  Specifically, when one type of object 9 (hereinafter referred to as “third object”) 9 is placed on the conveyor 2, the third object 9 moves at a constant speed. Then, the pulse width of the flash light from the LED 31 is determined based on the moving speed (and the desired resolution) of the third object 9, and an image of the inspection region on the third object 9 is acquired at the desired resolution. The

  Subsequently, a different type of object (hereinafter referred to as “fourth object”) 9 different from the third object 9 is placed on the conveyor 2, and the type of processing applied to the fourth object 9 is changed. Accordingly, the motor 24 rotates at a rotational speed that is decelerated accordingly, and the fourth object 9 moves at a slower speed than the third object 9. In the control unit 4, the pulse width of the flash light from the LED 31 is determined based on the moving speed of the third object 9. For example, when the moving speed of the fourth object 9 is 0.8 times the moving speed of the third object 9, the pulse width of the flash light is 1 as compared with the condition for the third object 9. /(0.8) times. When the inspection area on the fourth object 9 reaches the imaging position, flash light is emitted with the determined pulse width, and an image of the inspection area on the fourth object 9 is displayed on the third object 9. Acquired at the same resolution as the case.

  As described above, in the image acquisition device 1 in this operation example, the control unit 4 changes the pulse width of the flash light based on the moving speed of the object 9. Thereby, even when the moving speed of the object 9 is different, an image can be stably acquired at a desired resolution while matching the moving speed of the object 9. Note that the rotation speed of the motor 24 of the conveyor 2 may be controlled by the control unit 4. In this case also, the pulse width of the flash light is changed based on the moving speed of the object 9 obtained from the rotation speed of the motor 24. The

  Further, in the above embodiment, the description has been made from the viewpoint of using the LED 31 instead of the xenon lamp. However, the LED 31 of the image acquisition device 1 is 10 seconds since it is difficult to realize with the general xenon lamp. A flash light having a long pulse width may be emitted. In this case, considering the lifetime of the LED 31, the pulse width of the flash light is preferably 1 millisecond (msec) or less.

  Further, in the image acquisition device 1, the light amount of the flash light may be changed according to the object 9 by the control unit 4. In this case, the supply current to the LED 31 and the pulse width of the flash light according to the changed light amount. Is determined, and an image of the inspection region on the object 9 is appropriately acquired.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  When there are a plurality of inspection regions on one object 9 in the above-described operation example of acquiring an image at different limit resolutions and the operation example of acquiring an image of the object 9 moving at different speeds. Alternatively, flash light may be emitted from the LED 31 at a cycle of 1/300 seconds or less, and an image may be acquired at a short cycle.

  In the above embodiment, the object 9 moves relative to the fixed imaging device 33, but a moving mechanism that moves the imaging device 33 relative to the fixed object 9 may be provided. That is, the movement of the object 9 relative to the imaging device 33 may be relative.

  The microscope 32 in the above embodiment guides the reflected light of the flash light from the object 9 to the imaging device 33. Depending on the type of the object 9, the light passes through the object 9 in the irradiated flash light. Light may be guided to the imaging device 33. That is, the microscope 32 may be anything as long as it guides the light from the object 9 derived from the flash light to the imaging device 33. Depending on the design of the image acquisition apparatus, the imaging device 33 may be provided with a mechanical shutter.

  Further, in the image acquisition device 1, by irradiating the object 9 with flash light of 10 μsec or less in a very short period (so-called burst lighting), the light irradiated on the object 9 is reduced. It is also possible to increase the amount.

It is a figure which shows the structure of an image acquisition apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image acquisition apparatus 2 Conveyor 4 Control part 9 Object 31 LED
32 Microscope 33 Imaging device

Claims (8)

An image acquisition device for acquiring an image of a predetermined area on an object,
An imaging device;
A moving mechanism for moving an object relative to the imaging device;
A light emitting diode that irradiates flash light toward an object when a current exceeding an allowable current during continuous lighting is input,
An optical system for guiding light from an object derived from the flash light to the imaging device, and forming an image of a predetermined area on the object on the imaging device;
A control unit for controlling light emission of the light emitting diode and imaging by the imaging device;
An image acquisition apparatus comprising: The image acquisition device according to claim 1,
The image acquisition apparatus according to claim 1, wherein a current input to the light emitting diode is five times or more of the allowable current. The image acquisition device according to claim 1 or 2,
An image acquisition apparatus, wherein a pulse width of the flash light is 1 millisecond or less. The image acquisition device according to any one of claims 1 to 3,
The image acquisition apparatus according to claim 1, wherein the light emitting diode emits the flash light at a period of 1/300 seconds or less. The image acquisition device according to any one of claims 1 to 4,
The image acquisition apparatus, wherein the control unit changes a pulse width of the flash light. The image acquisition device according to claim 5,
The image acquisition apparatus, wherein the control unit changes the pulse width of the flash light based on a relative moving speed of an object with respect to the imaging device. The image acquisition device according to claim 6,
The image acquisition apparatus, wherein the control unit changes a light amount of the flash light according to an object. The image acquisition device according to claim 5,
The magnification of the optical system is variable,
The image acquisition apparatus, wherein the control unit changes the pulse width of the flash light based on the magnification of the optical system.

Images