JP2008232976A - Image inspection method and image inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image inspection method and image inspection device, which inspects an inspecting object accurately in a short period of time, based on an image acquired by imaging the inspecting object. <P>SOLUTION: The image inspection method comprises: an initial image acquisition process S4 of acquiring initial image information; a positional information acquisition process S5 of acquiring positional information of the inspecting object located at an initial imaging region based on the initial image information; an imaging region setting process S6 of setting the positions and areas of one or more imaging regions for imaging the other part that is not included in the initial imaging region of area of the inspecting object based on the positional information; an inspection image acquisition process S8 of acquiring inspection image information by imaging the set imaging region with an imaging means; and an image signal adjusting process S3 of adjusting each signal level of the initial image information and inspection image information to the same level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image inspection method and an image inspection apparatus.

2. Description of the Related Art Conventionally, there is known a CCD camera device that employs a CCD (Charge Coupled Device) element as an imaging element that converts an optical image of an inspection object into an electrical signal, and images the inspection object.
As this CCD camera device, there is known a device capable of imaging and outputting only a partial area without imaging the entire imaging area (see, for example, Patent Document 1).
In this CCD camera device, the amount of image data can be reduced by reducing the image pickup area to a part. As a result, even with the same dot clock, it is possible to increase the frame rate, which is the number of acquisitions or acquisition speed of image information that can be updated per second, and to shorten the transfer time of image information.

JP 2004-104561 A

However, when the imaging area is reduced, the exposure time (imaging time) of each imaging element is shortened as the frame rate increases, so the image becomes darker than when the imaging area is large, and the captured image There was a problem that the signal level of the information was also different.
That is, when the imaging range (area) is different in each imaging region, the exposure time of each imaging element is also different, and the brightness of the captured image, that is, the signal level is different. When an inspection object is inspected based on image information having different signal levels, there is a problem that an error occurs in the determination result because the signal levels are different.

  An object of the present invention is to provide an image inspection method and an image inspection apparatus capable of inspecting an inspection object with high accuracy and in a short time based on an image obtained by imaging the inspection object.

  The image inspection method of the present invention includes an initial image acquisition step of acquiring an initial image information by capturing an initial image area including a part of an inspection object with an imaging unit, and an initial image area based on the initial image information. A position information acquisition step of acquiring position information of the object to be inspected, and positions of one or more imaging regions that image other parts not included in the initial imaging region of the object to be inspected based on the position information An imaging region setting step for setting the area, an inspection image acquisition step for acquiring the inspection image information by imaging the imaging region set in the imaging region setting step by the imaging means, and the initial image information and the inspection image information. And an image signal adjustment step of adjusting each signal level to the same level.

  According to the present invention, in the initial image acquisition step, for example, initial image information including a part of the inspection object is acquired by setting the imaging region to the maximum. In the position information acquisition step, the initial image information is acquired. Since the position information of the object to be inspected is acquired based on the above, even if the object to be inspected is roughly arranged, the position information can be automatically acquired and the inspection can be automated. As a method for acquiring the position information of the inspection object from the initial image information, the arrangement area of the inspection object is extracted by image processing or the like using the luminance difference between the inspection object and the background portion. Good.

Furthermore, in the imaging area setting step, the minimum and necessary values are set because the position and area of the imaging area for imaging other parts of the inspection object not included in the initial imaging area are set based on the acquired position information. It can be set to a limited imaging area.
For example, when a long inspection object is divided into a plurality of imaging areas and inspected, one or more imaging areas must be set in addition to the initial imaging area to image the inspection object. In this case, each imaging area needs to include a portion where the object to be inspected is arranged, but in the present invention, it is obtained from information such as the shape and dimensions of the object to be inspected in advance and the initial image information. Since the position of the inspection object can be detected by using the position information of the inspection object, the imaging region can be set to a predetermined range including the inspection object.
For this reason, even if the initial imaging area is set to the maximum area, the other imaging areas can be set to the minimum size, and accordingly, the imaging time can be shortened in the inspection image acquisition process, and the inspection object can be shortened. Overall inspection time can be shortened.
In addition, in the image signal adjustment step, the signal levels of the initial image information and the inspection image information are adjusted to the same level, so that the brightness of each image information is the same level even if the area of the imaging region is different. it can. Therefore, in the inspection of the inspection object based on the image information, the possibility of an error can be reduced, and the inspection object can be inspected with high accuracy and in a short time.

  In the present invention, the position information acquisition step acquires at least an arrangement position of the inspection object and an extension direction of the inspection object in the initial image information as the position information of the inspection object, and the imaging region setting step includes the inspection area setting step. It is preferable to set the position and area of the imaging region based on the dimension in the extension direction of the inspection object and the arrangement position and extension direction of the inspection object.

Here, in the position information acquisition step, for example, in the initial image information, the coordinates of the X axis and the Y axis are set, and the coordinate positions of both ends of the inspection object in the initial image information are obtained, whereby the inspection object What is necessary is just to acquire an arrangement position. Similarly, the extension direction of the inspection object can be determined that the inspection object is continuous in the extension direction if the inspection object reaches the outer edge of the initial image information. It may be calculated based on
In the imaging region setting step, the dimension in the extension direction of the inspection object is measured in advance, and the range of the remaining portion of the inspection object exists from the information on the position of the inspection object and the extension direction. It is only necessary to set the number of imaging areas necessary for imaging the remaining part of the inspection object, and the position and area of each imaging area.

  According to such a configuration, the position and area of each imaging region can be automatically obtained based on the arrangement state of the inspection object, and it is not necessary to position and inspect the inspection object in advance. The work process can be easily automated. In addition, the entire inspection object can be divided into a plurality of areas and reliably imaged, and each part of the inspection object can be enlarged and imaged using a microscope or the like, and a fine part is also inspected. be able to.

In the present invention, it is preferable that the imaging region setting step sets the area of the imaging region to be smaller than the area of the initial imaging region.
When the object to be inspected is long and thin, for example, a line head of an electrophotographic printer, a cylindrical platen, or the like, the longitudinal direction of the object is almost in the Y-axis direction in the XY coordinates set in the captured image information. When arranged so as to be along, it is sufficient that the width dimension in the X direction of the imaging region is within a dimension obtained by adding a certain margin to the width dimension of the object to be inspected.
Accordingly, when a plurality of imaging areas are provided along the extension direction (Y-axis direction) of the object to be inspected, even if the maximum initial area is set in the initial initial imaging area, The width dimension in the X direction can be reduced. Thereby, the imaging time of an inspection image acquisition process can be shortened, and the inspection time of a to-be-inspected object can be shortened significantly.

  In the present invention, the image pickup unit includes an image pickup element that converts an optical image into an electric signal, and has an electronic shutter function that controls a shooting time of the image pickup element. Even when the areas differ in area, it is preferable that the signal level of each image information is adjusted to be constant by making the electronic shutter time constant by the electronic shutter function.

When an imaging device such as a CCD is used, the imaging time can be controlled by an electronic shutter. Therefore, even when the area of the imaging region is different, the electronic shutter time is made constant so that the imaging conditions in each image acquisition step Specifically, the exposure time becomes equal, and the signal level of each image information can be made constant.
Since the electronic shutter time can be easily controlled and the signal level of each image information can be made constant at the time of image capture, there is no need to correct the image information later, and a high-accuracy inspection can be performed in a short time. And can be done easily.

Here, in the image signal adjustment step, it is preferable that the electronic shutter time is set to a shortest time that can be set by an electronic shutter function.
In the present invention, since the shutter time is set to the shortest settable time, all image information (initial image information and each inspection image information) can be acquired with the shortest imaging time and the same signal level. Highly accurate inspection can be performed in a short time.
The shortest electronic shutter time is an electronic shutter time that is set when an image sensor that can change the imaging area captures an image of the minimum imageable area that can be set. With this electronic shutter time, it is possible to image even in an imaging region longer than that, so that imaging can be performed regardless of the size of the imaging region, and the signal level of the captured image information can be made the same level.

  In the present invention, the image pickup unit includes an image pickup device that converts an optical image into an electrical signal, and the image signal adjustment step is performed by the image pickup device when an image pickup region having the smallest area is picked up in each image pickup region. When photographing another imaging region with the signal level of the obtained image information as a reference, it is preferable to adjust the signal level of the image information according to the signal level of the minimum imaging region.

  In the present invention, since the signal level of each image information is matched with the image information obtained by imaging the imaging area with the smallest area, all image information (initial image information and each Inspection image information) can be acquired, and a highly accurate inspection can be performed in a short time.

  Here, in the image signal adjustment step, the method of adjusting the signal level of the image information by reducing the amount of light entering the image sensor with an aperture adjustment or a neutral density filter when imaging the other imaging region, the imaging It is preferable to execute any one of a method for adjusting the signal level of the image information by adjusting an amplifier gain of the element and a method for adjusting the signal level by image processing the image information.

That is, when the imaging time becomes longer because the imaging area is large, the imaging area with the smallest area is imaged by reducing the amount of light entering the imaging element by using aperture adjustment or a neutral density filter (ND filter). The signal level of each piece of image information can be made constant.
In addition, the amplifier gain of the image sensor is adjusted to increase the signal level of image information when the imaging area is minimum, or to decrease the signal level of image information when the imaging area is large, thereby relating to the area of the imaging area. The signal level can be kept constant.
Further, by adjusting the signal level of the image information by post-processing, even if the signal level of the image information at the time of output from the image sensor does not match, the image information used in the inspection process has the signal level. Can be constant.
Therefore, the imaging time of each imaging region can be shortened according to the area of the region, and the signal level of the image information can be made constant regardless of the area of the imaging region, and high-precision inspection can be performed in a short time. Can be done.

An image inspection apparatus according to the present invention includes an initial image acquisition unit that acquires an initial image information by imaging an initial imaging region including a part of an inspection object with an imaging unit, and an initial imaging region based on the initial image information. Position information acquisition means for acquiring position information of the object to be inspected, and positions of one or more imaging regions that image other parts not included in the initial imaging region of the object to be inspected based on the position information An imaging area setting means for setting the area, an inspection image acquisition means for acquiring the inspection image information by imaging the imaging area set by the imaging area setting means by the imaging means, the initial image information and the inspection image information Image signal adjusting means for adjusting each signal level to the same level.
According to the present invention, the same effects as those of the above-described image inspection method can be obtained.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
In the first embodiment, an apparatus that performs image inspection of a line head of an electrophotographic printer as an object to be inspected will be described as an example with reference to FIGS.

In the line head, a plurality of LEDs are arranged along the longitudinal direction. For example, about 7000 LEDs are arranged in a 600 dpi printer. In an LED printer, each LED light is imaged on a photosensitive drum through a rod lens array to form an electrostatic latent image, and therefore it is necessary to inspect whether the LED light is properly output from the line head. There is.
In view of this, the line head is turned on to take an image and the image information is inspected for defects and the like. This embodiment is used for such an inspection.

FIG. 1 is a schematic configuration diagram illustrating a configuration of an image inspection apparatus 10 according to the first embodiment.
The image inspection apparatus 10 operates the CCD camera 1, the microscope 2 installed on the lens side of the CCD camera 1, the feed stage 3, the CCD camera 1, the feed stage 3, and the line head 20 as an inspection object. And a control unit 4 for controlling.

The CCD camera 1 includes a CCD element that is an image pickup element that picks up an image of the line head 20 and converts the optical image into an electric signal. The control unit 4 controls the CCD camera 1 by sending a camera control signal.
The optical image of the line head 20 is magnified by the microscope 2, further converted into an electrical signal by the CCD element, and transferred to the control unit 4 of the image inspection apparatus 10. Thereby, the line head 20 is imaged by the image inspection apparatus 10.

  As shown in FIG. 2, the CCD camera 1 is configured so that the imaging region 11 can be divided into a plurality of regions (blocks). Each divided block is set with a block number. By setting a start block number and an end block number in the camera control signal for controlling the CCD camera 1, only the area between the block numbers is imaged and image information is obtained. It is configured to allow output. For example, as shown in FIG. 2, when the imaging area 11 is set to be divided into 13 areas from block 1 to block 13, if the start block number is “6” and the end block number is “10”, As shown in FIG. 3, only the area 12 from the blocks 6 to 10 becomes the effective imaging area, and only the image information of this effective imaging area is output from the CCD camera 1.

  The CCD camera 1 has an electronic shutter function for setting an electronic shutter time. For this reason, the control part 4 can set exposure time as imaging conditions by setting electronic shutter time using an electronic shutter function.

  The microscope 2 is installed outside the lens of the CCD camera 1 and enlarges the optical image of the line head 20. The enlarged optical image of the line head 20 is picked up by the CCD camera 1.

The feed stage 3 includes a table 31 on which the line head 20 is disposed and a table driving unit 32. When the direction of the arrow 33 in FIG. 1 is set as the Y-axis direction, the table driving unit 32 is configured to be able to move the table 31 linearly in the Y-axis direction, and is driven and controlled by a stage control signal from the control unit 4.
The table drive unit 32 includes a drive mechanism such as a servo motor or a stepping motor, a ball screw that converts rotational motion by the drive mechanism into linear movement, and a linear guide that is connected to the ball screw and performs linear movement with high accuracy. As an example, a configuration including

  In the line head 20, lighting of each LED is controlled by a line head control signal from the control unit 4.

Hereinafter, the structure of the control part 4 is demonstrated based on FIG.
The control unit 4 outputs a line head control signal to the line head 20 and controls the line head control means 41, a feed stage drive means 42 that outputs and controls a stage control signal to the feed stage 3, A camera control unit 43 that outputs and controls a camera control signal to the CCD camera 1; an image acquisition unit 44 that captures image information captured by the CCD camera 1 into the control unit 4 via a video capture board; And an image inspection control means 45.

  The image inspection control unit 45 includes an initial image acquisition unit 46 that acquires initial image information using the CCD camera 1, and a position information acquisition unit 47 that acquires position information of the line head 20 based on the acquired initial image information. The imaging area setting means 48 for setting the imaging area based on the position information and the dimension information of the line head 20, the inspection image acquisition means 49 for acquiring the image of the set imaging area, and the signal level of each image information Are adjusted to the same level, and image inspection means 51 for inspecting the line head 20 based on each image information whose signal level is adjusted.

Next, an image inspection method in the image inspection apparatus 10 according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 5, the image inspection method of the present embodiment includes a line head control step S1, a feed stage drive step S2, an image signal adjustment step S3, an initial image acquisition step S4, and a position information acquisition step S5. An imaging region setting step S6, a feed stage driving step S7, an inspection image acquisition step S8, an imaging completion determination step S9, and an image inspection step S10 for determining whether the line head 20 is good or bad.

  When the inspection of the inspection object is instructed, the control unit 4 first performs the line head control step S1. In the line head control step S1, the line head control means 41 performs control to turn on the LEDs of the line head 20.

  Next, the control unit 4 performs a feed stage driving step S2. In the feed stage drive step S2, the table 31 is moved linearly by the feed stage drive means 42 and moved to a predetermined position. Specifically, as shown in FIG. 6A, one end of the line head 20 moves to a position included in the initial imaging area 11 </ b> A of the CCD camera 1.

In this embodiment, the position where the line head 20 is arranged on the table 31 is roughly determined, and when the table 31 is moved to the right end which is one end of the driveable range of the feed stage 3 in FIG. One end of the head 20 is set to move to a position included in the initial imaging area 11A of the CCD camera 1.
As a method of moving the table 31 to such a position, for example, the feed stage 3 may be linearly moved from the right end, which is one end of the driveable range of the feed stage 3, to the left side, and determined by a sensor (not shown). The image may be determined by repeating the imaging by the CCD camera 1 and the movement of the table 31 until the line head 20 is imaged and the end of the line head 20 is detected.

Next, the control unit 4 performs the image signal adjustment step S3 using the image signal adjustment means 50. In the image signal adjustment step S3, the electronic shutter time t1 of the CCD camera 1 is set. In other words, in this embodiment, the minimum object area is 5 blocks in consideration of the margin when the object to be measured is a long line head 20 and the width of the object is inclined with respect to the Y-axis direction. Set to minutes.
Therefore, the image signal adjusting means 50 sets the electronic shutter time to the electronic shutter time t1 when imaging the imaging area 12 for five blocks as shown in FIG.

The electronic shutter time may be set to a time set when one block in the imaging area 11 is imaged. That is, the electronic shutter time may be set to the shortest time that can be set by the electronic shutter function.
Further, since the line head control step S1, the feed stage driving step S2, and the image signal adjustment step S3 can be processed in parallel, the order of processing is not limited to the order of the present embodiment, You may perform each process simultaneously.

Next, the control unit 4 performs the initial image acquisition step S4 by the initial image acquisition means 46. That is, the initial image acquisition means 46 outputs a camera control signal to the CCD camera 1 via the camera control means 43, and as shown in FIG. Imaging is performed at the electronic shutter time t1.
Then, the captured initial image information is acquired via the image acquisition means 44.

Next, the control unit 4 uses the position information acquisition unit 47 to perform a position information acquisition step S5. In the position information acquisition step S5, position information of the line head 20 located in the initial imaging region 11A shown in FIG. 6A is acquired.
That is, the position information acquisition unit 47 analyzes the acquired initial image information, and the extension direction dimension L, the width direction dimension W of the line head 20 located in the initial imaging region 11A, the extension direction of the line head 20, specifically, The inclination angle θ with respect to the Y-axis direction of the table 31 is acquired. The inclination angle θ can be calculated, for example, by detecting at least two intermediate points of the width direction dimension W of the line head 20 at, for example, points A and B at both ends of the line head 20 in the initial image information.

Next, the control unit 4 performs the imaging region setting step S <b> 6 by the imaging region setting means 48. In the imaging area setting step S6, the subsequent imaging area is calculated and set based on the position information.
In the present embodiment, since the relative position between the CCD camera 1 and the line head 20 is changed by moving the table 31 in the Y-axis direction, the subsequent imaging area is the imaging area 12A shown in FIG. Like the imaging region 12B shown in FIG. 6C, the position in the Y-axis direction is set to a position that differs by the size of the imaging region 11 in the Y-axis direction.
The block positions and numbers of the imaging regions 12A and 12B, that is, the start block number and the end block number are set based on the position information of each line head 20 so that the line head 20 is included.
For this reason, the imaging areas 12A and 12B can have a smaller area than the initial imaging area 11A, and are configured by limited blocks.

  Next, the control unit 4 performs the feed stage driving step S7 by the feed stage driving means 42, and linearly moves the table 31 to the left by a certain amount of movement (Y-axis dimension of the imaging region 11). The area imaged by the CCD camera 1 is moved to the imaging area 12A.

Thereafter, the control unit 4 performs the inspection image acquisition step S8 by the inspection image acquisition means 49. Specifically, the inspection image acquisition unit 49 uses the CCD camera at the start block number and end block number of the imaging region 12A set in the imaging region setting step S6 and the electronic shutter time t1 set in the image signal adjustment step S3. 1 is controlled. In the example of FIG. 6B, the start block number is “6” and the end block number is “10”.
Then, inspection image information output from the CCD camera 1 is acquired.

Next, the control unit 4 performs an imaging completion determination step S9, and determines whether all imaging of the imaging region set in the imaging region setting step S6 has been completed.
If the imaging has not been completed, the feed stage driving step S7 and the inspection image acquisition step S8 are repeated, the next imaging region 12B is imaged, and the inspection image information is acquired.
In FIG. 6, the entire line head 20 is typically imaged by three times of imaging. However, since the image is actually magnified by the microscope 2, the area that can be imaged in one imaging area is very small. The 600 dpi line head 20 in which about 7000 LEDs are arranged is divided into about 500 imaging regions, so that the feed stage drive step S7 and the inspection image acquisition step S8 are repeated about 500 times.

When it is determined that the imaging is completed in the imaging completion determination step S <b> 9, the control unit 4 performs the image inspection step S <b> 10 by the image inspection unit 51.
In the image inspection step S10, the brightness and area of the LED portion are analyzed based on the initial image information acquired by the initial image acquisition unit 46 and each inspection image information acquired by the inspection image acquisition unit 49, and Inspect for defects. At this time, since each image information has the same electronic shutter time t1, if the brightness of the LEDs is the same, the image signal has the same signal level. Therefore, in each image information, if there is an LED that is much darker than the other LEDs, it can be detected that the LED is defective.

  Thus, the inspection of the line head 20 is completed. When inspecting another line head 20, the line head 20 may be placed on the table 31 and the above-described line head control step S1 to image inspection step S10 may be executed.

According to this embodiment, there are the following effects.
(1) Since the imaging area setting means 48 sets and captures the minimum imaging areas 12A and 12B for imaging the line head 20, all of the line heads 20 are divided and imaged. Compared to the case where the imaging region is the maximum imaging region 11A, the image acquisition time can be shortened, the inspection time of the line head 20 can be shortened, and the inspection efficiency can be improved.

(2) Since the initial image acquisition means 46 and the position information acquisition means 47 obtain the position information of the line head 20, and the imaging area setting means 48 sets the imaging areas 12A and 12B based on the position information, the table Even when the position of the line head 20 is slightly shifted when the line head 20 is disposed on the line 31, the position of the line head 20 can be detected accurately and automatically. For this reason, even if the imaging areas 12A and 12B set by the imaging area setting means 48 are set to the minimum size, the line head 20 can be reliably arranged in the area, and the inspection image information can be acquired reliably. .

(3) Even if the sizes of the imaging regions 11A, 12A, and 12B are different, the electronic shutter time t1 is made constant, so that the signal level of each image information can be made constant. Therefore, variations in the brightness of the LEDs can be easily detected from each piece of image information, the image information need not be corrected, and the quality determination of the line head 20 can be performed accurately and in a short time.

(Second Embodiment)
Next, a second embodiment of the present invention will be described based on the flowchart of FIG. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

In the first embodiment, the electronic shutter time t1 is set in the image signal adjustment step S3, and the signal level of the image information is set by making the electronic shutter time t1 constant when imaging each imaging region 11A, 12A, 12B. It was constant.
On the other hand, in the second embodiment, the signal level is made constant by performing image correction processing after acquiring image information. For this reason, as shown in FIG. 7, after all the imaging is completed in the imaging completion determination process S9, an image signal adjustment process S11 for making the signal level of each acquired image information constant is performed.

  In the image signal adjustment step S11, for example, in each image information, the signal level of a common reference portion is compared, and correction processing may be performed so that the difference is eliminated. The common reference portion may be a portion where the signal level is constant in any of the imaging regions, such as the frame portion of the line head 20, when imaging is performed in each of the imaging regions 11A, 12A, and 12B. . Further, in each of the imaging regions 11A, 12A, and 12B, a reference LED may be disposed adjacent to the line head 20, and the brightness of the reference LED may be corrected so as to match in each image information.

According to such 2nd Embodiment, there can exist the same effect as the said 1st Embodiment.
Furthermore, in the first embodiment, since the electronic shutter time t1 is set in advance in accordance with the areas of the imaging regions 12A and 12B (5 blocks in the embodiment), imaging is performed in a smaller area in the imaging region setting step S6. The area cannot be set. On the other hand, in this embodiment, since the signal level can be made constant in the image processing after imaging, the area at the time of imaging can be adjusted each time, for example, while the inspection image acquisition is being repeated, 4 blocks It is also possible to change to an imaging area of minutes, and the imaging time can be further shortened accordingly.

(Modification)
It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the first embodiment, in the image signal adjustment step S3, the number of blocks of the imaging regions 12A and 12B is set to 5, and the electronic shutter time t1 when imaging the imaging regions 11A, 12A, and 12B is Although the time for imaging the area for 5 blocks is set, it may be set to the shortest settable time, specifically, the time for imaging the area for 1 block.
When configured in this manner, it is possible to capture an image in any imaging region from one block to all blocks (13 blocks), and the signal level of the captured image information can be made constant.

Further, the method of making the signal level of the image information constant is not limited to the method of making the electronic shutter time t1 constant as in the first embodiment and the method of performing image processing as in the second embodiment.
For example, an ND filter (Neutral Density Filter) that reduces the amount of light entering the lens of the CCD camera 1 can be placed either between the lens of the microscope 2 and the line head 20 or between the CCD camera 1 and the microscope 2. In addition, by using an ND filter, the light level may be adjusted according to the area of the imaging region to make the signal level constant.

  That is, when the electronic shutter time is not adjusted to be constant, the imaging time, that is, the exposure time becomes longer as the area of the imaging region becomes larger, and the amount of light entering the CCD camera 1 increases accordingly. Therefore, for example, when the imaging area is minimized, the light quantity entering the CCD camera 1 is used as a reference, and as the imaging area becomes larger, the ND filter is used to reduce the light quantity so as to match the reference light quantity. The signal level of the image information may be constant.

  Further, as a method of reducing the amount of light entering the lens of the CCD camera 1, a method of adjusting the aperture by providing an aperture mechanism in the CCD camera 1 may be adopted.

  Further, in the CCD camera 1, the signal level of each image information may be made constant by using an amplifier gain function for electrically amplifying the electric signal converted by the CCD element. That is, when the electronic shutter time is not constant, the signal level of the image information having the largest imaging area becomes the highest, and the signal level decreases as the area of the imaging area becomes smaller. Therefore, the signal level of the inspection image information in each of the imaging regions 12A and 12B can be matched with the signal level of the initial image information in the initial imaging region 11A by amplifying the lowered signal level with the amplifier gain function.

  In the above-described embodiment, the image inspection step S10 is performed after all the imaging regions are imaged. For example, an image of the reference line head 20 and the line head 20 of the inspection object are imaged. When determining pass / fail by comparing the image, the reference image and the signal level are set so as to coincide with each other, and each time the image pickup area is imaged in the test image acquisition step S8, The image inspection step S10 may be performed by comparing with the reference image.

Furthermore, in the above-described embodiment, the position information of the line head 20 that is the inspection object is obtained based on the initial image information, and the imaging regions 12A and 12B are set in advance in the imaging region setting step S6. The position information of the inspection object may be obtained each time based on the image information acquired in the acquisition step S8, and the next imaging area may be set. In this way, since the next imaging area is set based on the position information of the immediately preceding inspection object, the imaging area can be set with higher accuracy. In particular, when the object to be inspected is curved or the shape is not known, the imaging region can be set with high accuracy, and the object to be inspected can be reliably imaged.
In this case, since the minimum area of the imaging region cannot be predicted first, when the electronic shutter time is made constant, as described above, when capturing an area for one block, which is the minimum area of the imaging region, The time may be set.

  In the above embodiment, the table 31 is moved. However, the CCD camera 1 side may be moved. In short, the object to be measured and the CCD camera 1 need only be relatively movable.

Furthermore, the moving direction of the table 31 is not limited to a single axial direction, and may be configured to have a structure that can move in two axial directions or three axial directions, and the table 31 is rotated about the axis. It is good also as a structure provided with a means.
These may be set according to measurement conditions such as the shape of the object to be measured.

The object to be measured of the present invention is not limited to the line head 20 of the electrophotographic printer. In particular, it is preferably a long object extending in the longitudinal direction with a certain width dimension, and may be a platen of a printer, for example.
The present invention can be widely applied to various image inspections that can be inspected based on the brightness of image information such as a surface scratch on a long object to be measured and the brightness of a light source.

1 is a schematic configuration diagram showing a configuration of an image inspection apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram for explaining an imaging area of the CCD camera. FIG. 3 is a diagram for explaining an imaging area of the CCD camera. The block diagram which shows the structure of the control part of an image inspection apparatus. 6 is a flowchart illustrating an image inspection method according to the first embodiment. FIG. 6A is an explanatory diagram illustrating an initial imaging area in the initial image acquisition process, and FIGS. 6B and 6C are explanatory diagrams illustrating an imaging area in each inspection image acquisition process. 9 is a flowchart for explaining an image inspection method according to the second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... CCD camera, 2 ... Microscope, 3 ... Feed stage, 4 ... Control part, 10 ... Image inspection apparatus, 11, 12, 12A, 12B ... Imaging area, 11A ... Initial imaging area, 20 ... Line head, 31 ... Table , 32 ... Table drive unit, 41 ... Line head control means, 42 ... Feed stage drive means, 43 ... Camera control means, 44 ... Image acquisition means, 45 ... Image inspection control means, 46 ... Initial image acquisition means, 47 ... Position Information acquisition means 48 ... Imaging region setting means 49 ... Inspection image acquisition means 50 ... Image signal adjustment means 51 ... Image inspection means

Claims (8)

An initial image acquisition step of acquiring an initial image information by imaging an initial imaging region including a part of the inspection object with an imaging unit;
A position information acquisition step of acquiring position information of an object to be inspected located in an initial imaging region based on the initial image information;
An imaging region setting step for setting the position and area of one or more imaging regions that image other parts not included in the initial imaging region of the inspection object based on the position information;
An inspection image acquisition step of acquiring the inspection image information by imaging the imaging region set in the imaging region setting step by the imaging means;
An image signal adjustment step of adjusting each signal level of the initial image information and the inspection image information to the same level;
An image inspection method comprising: The image inspection method according to claim 1,
In the position information acquisition step, as the position information of the inspection object, at least the arrangement position of the inspection object in the initial image information and the extension direction of the inspection object are acquired,
The imaging region setting step sets a position and an area of the imaging region based on a dimension in an extension direction of the inspection object and an arrangement position and an extension direction of the inspection object. Method. The image inspection method according to claim 1 or 2,
In the imaging region setting step, the area of the imaging region is set smaller than the area of the initial imaging region. The image inspection method according to any one of claims 1 to 3,
The imaging means includes an image sensor that converts an optical image into an electrical signal, and has an electronic shutter function that controls a shooting time of the image sensor,
In the image inspection method, the signal level of each piece of image information is adjusted to be constant by making the electronic shutter time constant by the electronic shutter function even when the areas of the respective imaging regions are different. The image inspection method according to claim 4,
In the image signal adjusting step, the electronic shutter time is set to the shortest time that can be set by an electronic shutter function. The image inspection method according to any one of claims 1 to 3,
The imaging means includes an imaging element that converts an optical image into an electrical signal,
The image signal adjustment step is based on the signal level of image information obtained by the image sensor when the imaging area having the smallest area in each of the imaging areas is imaged.
An image inspection method characterized by adjusting a signal level of image information in accordance with a signal level of the minimum imaging area when imaging another imaging area. The image inspection method according to claim 6,
The image signal adjusting step includes a method of adjusting a signal level of the image information by reducing an amount of light entering the image pickup device with an aperture adjustment or a neutral density filter when photographing the other image pickup region, and an amplifier of the image pickup device An image inspection method, comprising: adjusting a gain to adjust a signal level of the image information; or performing an image process on the image information to adjust the signal level. An initial image acquisition means for acquiring an initial image information by imaging an initial imaging area including a part of the inspection object with an imaging means;
Position information acquisition means for acquiring position information of an inspection object located in an initial imaging region based on the initial image information;
An imaging area setting means for setting the position and area of one or more imaging areas for imaging other parts not included in the initial imaging area of the inspection object based on the position information;
Inspection image acquisition means for acquiring the inspection image information by imaging the imaging area set by the imaging area setting means by the imaging means;
Image signal adjusting means for adjusting the signal levels of the initial image information and the inspection image information to the same level;
An image inspection apparatus comprising:

Images