CN111398295A - Defect detection device and method thereof - Google Patents

Abstract

The invention discloses a defect detection device and a method thereof, wherein the device drives a workpiece table to move along the push-broom direction of a time delay integral camera by controlling a driving motor, and the time delay integral camera acquires an actually measured object image element when the workpiece table moves once according to a preset step length; the displacement measuring unit measures the actual displacement of the workpiece platform once when the workpiece platform moves once according to the preset step length; the control unit is used for determining a standard object image element to be detected according to the actually measured object image element to be detected and the preset step length, and adjusting the preset step length of the next movement of the workpiece platform according to the current actual displacement until the time delay integral camera finishes scanning the object to be detected to obtain a plurality of standard object image elements to be detected; sequentially splicing a plurality of standard object image elements to form a standard object image; and defect detection is carried out on the object to be detected according to the standard object image, so that the standard object to be detected image is clearer, and the defect of the object to be detected is better identified.

Description

A defect detection device and method thereof

technical field

The invention relates to the technical field of optical measurement and detection, and in particular, to a defect detection device and a method thereof.

Background technique

Automatic Optical Inspection (AOI) is a device that detects common defects encountered in welding production based on optical principles. It can achieve fast, high-precision, and non-destructive inspection of the object to be measured. It is now widely used in PCBs. , IC chips, wafers, LED, TFT and solar panels and other fields. Automatic optical inspection technology generally uses a high-precision optical imaging system to image the object to be measured, and the workpiece table carries the object to be measured for high-speed scanning to achieve high-speed measurement; the system compares the scanned image with an ideal reference image, or through feature extraction and other methods, Identify surface defects of the object to be tested.

Among them, the camera used in the automatic optical detection technology is usually a time delay integration (Time Delay Integration) camera. When the camera is taking pictures, especially during the high-speed scanning of the workpiece table, the position of the workpiece table may have errors due to the influence of servo, measurement, guide rail and other factors, which will lead to blurred images captured by the camera. And the larger the position error of the workpiece stage, the more blurred the image captured by the TDI camera.

SUMMARY OF THE INVENTION

The invention provides a defect detection device and a method thereof, so as to solve the problem of blurred images of the workpiece table due to the influence of error factors such as servo, measurement, and guide rails.

To achieve the above purpose, an embodiment of the present invention provides a defect detection device, including:

Workpiece table, used to carry the object to be tested;

a light source for emitting a detection beam, the detection beam illuminates the object to be tested, and is reflected or scattered by the object to be tested to form a beam to be imaged;

an optical imaging unit, located on the transmission path of the to-be-imaged light beam, for collecting the to-be-imaged light beam;

a time-delay integrator camera, located on the side of the optical imaging unit away from the object to be tested;

A driving unit, configured to drive the workpiece stage to move along the push-broom direction of the time-delay integral camera according to a preset step size, wherein each time the workpiece stage moves according to the preset step size, the time delay The integral camera obtains an image element of the measured object;

a displacement measuring unit, the displacement measuring unit measures the actual displacement of the workpiece table along the push-broom direction of the time-delay integral camera once every time the workpiece table moves according to the preset step size;

a control unit, which is electrically connected to the time-delay integrator camera, the displacement measurement unit, and the drive unit, respectively, and is configured to obtain a standard according to the measured object image element and the preset step size The image element of the object to be measured is adjusted, and the preset step size of the next movement of the workpiece table is adjusted according to the actual displacement of the current time, until the time-delay integral camera completes the scanning of the object to be measured to obtain a plurality of the image elements of a standard object to be tested; splicing a plurality of image elements of the standard object to be tested in sequence to form a standard image of the object to be tested; and performing defect detection on the object to be tested according to the image of the standard object to be tested.

Optionally, the control unit is further configured to determine the response function of the image element of the object to be measured according to the preset step size; determine the standard object to be measured according to the response function and the image element of the object to be measured. Object image element.

Optionally, the control unit is further configured to use a deconvolution operation to determine the standard object under test image element according to the response function and the actually measured object under test image element.

Optionally, the control unit is further configured to obtain the difference between the preset step size and the actual displacement; and determine the sum of the preset step size and the difference as the next time of the workpiece table. The preset step size for movement.

Optionally, the optical imaging unit includes a first optical lens and a second optical lens, the first optical lens is located on a side of the object to be measured away from the workpiece table, and the second optical lens is located on the The side of the first optical lens facing away from the workpiece stage, the first optical lens is used for collecting and collimating the light beam to be imaged, and the light beam to be imaged is converged at the time delay through the second optical lens camera.

Optionally, the displacement measuring unit is a laser interferometer or a grating ruler.

In order to achieve the above object, another embodiment of the present invention also provides a defect detection method, which is implemented based on the aforementioned defect detection device and includes the following steps:

Control the workpiece table to move along the push-broom direction of the time-delay integral camera with a preset step size;

Obtain the actual displacement of the workpiece table;

acquiring the measured object image element formed by the time-delay integral camera;

Acquiring a standard object image element according to the measured object image element and the preset step size;

Determine the preset step size for the next movement of the workpiece table according to the preset step size and the actual displacement; repeat the above steps in sequence until the time-delay integrator completes scanning the object to be tested to obtain multiple the standard object to be tested image element;

splicing a plurality of image elements of the standard object to be tested in sequence to form a standard object to be tested image;

Defect detection is performed on the test object according to the standard test object image.

Optionally, obtaining the standard object image element according to the measured object image element and the preset step size includes:

Determine the response function of the measured object image element according to the preset step size;

The standard object under test image element is determined according to the response function and the actually measured object under test image element.

Optionally, the determining the image element of the standard object to be measured according to the response function and the measured object image element includes:

The standard object to be tested image element is determined according to the response function and the measured object to be tested image element by using a deconvolution operation.

Optionally, determining the preset step size for the next movement of the workpiece table according to the preset step size and the actual displacement includes:

obtaining the difference between the preset step size and the actual displacement;

The sum of the preset step size and the difference value is determined as the preset step size for the next movement of the workpiece table.

To sum up, according to the defect detection device and method provided by the embodiments of the present invention, the workpiece table is driven to move in the push-broom direction of the time-delay integral camera by controlling the driving motor, and the workpiece table moves once every preset step size. , the time-delay integral camera obtains an image element of the object to be measured; each time the workpiece table moves according to the preset step size, the displacement measuring unit measures the actual displacement of the workpiece table along the push-broom direction of the time-delay integral camera; the control unit uses Obtain the standard object image element according to the measured object image element and the preset step size, and adjust the preset step size of the next movement of the workpiece table according to the current actual displacement until the predetermined step size is reached. The time-lapse integrator scans the object to be tested to obtain a plurality of image elements of the standard object to be tested; sequentially stitches a plurality of image elements of the standard object to be tested to form a standard image of the object to be tested; The standard object to be tested image is used for defect detection of the object to be tested, so that the image of the standard object to be tested is clearer and the defects of the object to be tested can be better identified.

Description of drawings

1 is a schematic structural diagram of a defect detection device according to an embodiment of the present invention;

2 is a schematic structural diagram of a displacement measurement unit in a defect detection device according to an embodiment of the present invention;

3 is a flowchart of a defect detection method proposed by an embodiment of the present invention;

4 is a flowchart of a defect detection method proposed by an embodiment of the present invention;

5 is a flowchart of a defect detection method proposed by another embodiment of the present invention;

FIG. 6 is a flowchart of a defect detection method proposed by another embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all structures related to the present invention.

FIG. 1 is a schematic structural diagram of a defect detection apparatus according to an embodiment of the present invention. As shown in Figure 1, the defect detection device proposed by the present invention includes:

The workpiece table 1 is used to carry the object to be tested 8;

The light source 2 is used to emit a detection beam 201, the detection beam 201 illuminates the object to be measured 8, and is reflected or scattered by the object to be measured 8 to form a beam 202 to be imaged;

The optical imaging unit 3 is located on the transmission path of the light beam 202 to be imaged, and is used to collect the light beam 202 to be imaged;

The time-delay integrator camera 4 is located on the side of the optical imaging unit 3 away from the object to be measured 8;

The driving unit 5 is used to drive the workpiece table 1 to move along the push-broom direction of the time-delay integral camera 4 according to the preset step size, and the time-delay integral camera 4 moves on the workpiece table 1 every time according to the preset step size to obtain an actual measurement The image element of the object to be tested;

The displacement measuring unit 6 is used to measure the actual displacement of the workpiece table 1 every time it moves according to the preset step size;

The control unit 7, the control unit 7 is electrically connected with the time-delay integral camera 4, the displacement measuring unit 6 and the driving unit 5 respectively, and is used for obtaining the standard object image element according to the measured object image element and the preset step size, and Adjust the preset step size of the next movement of the workpiece table 1 according to the actual displacement of the current time, until the time-delay integrator camera 4 completes the scanning of the object to be tested to obtain a plurality of image elements of the standard object to be tested; image element to form a standard image of the object to be tested; and perform defect detection on the object to be tested according to the image of the standard object to be tested.

Taking FIG. 1 as an example, the working principle of the defect detection device is as follows: the object to be tested 8 is placed on the workpiece table 1, the light source 2 emits a detection beam 201 to illuminate the object to be tested 8, and the detection beam 201 is reflected or scattered by the object to be tested. The beam 202 to be imaged, the beam 202 to be imaged enters the time-delay integrator camera 4 through the optical imaging unit 3, and the control unit 7 controls the drive motor 5 to drive the workpiece table 1 to move along the X direction in FIG. is the push-broom direction of the time-lapse integral camera 4). The time-lapse camera 4 forms a first measured object image element according to the light beam 202 to be imaged. The control unit 7 acquires the first standard object image element according to the first preset step size and the first measured object image element.

Optionally, the control unit 7 is further configured to determine the response function of the image element of the measured object to be measured according to the preset step size; and determine the image element of the standard object to be measured by using the response function and the image element of the measured object to be measured.

Optionally, the control unit 7 is further configured to use a deconvolution operation to determine the standard object under test image element according to the response function and the actually measured object under test image element.

Therefore, the control unit 7 performs a deconvolution operation on the image element of the first real object to be measured and its corresponding response function to obtain the image element of the first standard object to be measured.

After acquiring the image element of the first standard object to be measured, the control unit 7 controls the driving unit 5 to drive the workpiece table 1 to move along the X direction with a second preset step size, and the time-delay integrator 4 forms a second actual measurement according to the beam 202 to be imaged. The image element of the object to be tested is obtained, and the image element of the second standard object to be tested is obtained according to the second preset step size and the second actual measured image element of the object to be tested.

The control unit 7 performs a deconvolution operation on the image element of the second measured object to be tested and the corresponding response function to determine the second standard image element of the object to be tested.

And so on, until the time-delay integrator camera 4 traverses the entire object to be tested 8 on the workpiece table 1, the time-delay integrator camera 4 outputs a plurality of standard object-to-be-measured image elements, and sends them to the control unit 7, and the control unit 7 will They are sequentially spliced to form a standard object image of the entire object to be tested 8 , and the image of the standard object to be tested is clearer, which avoids the disturbance of the workpiece table 1 from affecting the imaging of the time-delay integral camera 4 . Furthermore, it is beneficial for the control unit 7 to detect and identify the defects of the object to be tested 8 according to the standard image of the object to be tested.

Optionally, the control unit 7 is further configured to acquire the difference between the preset step size and the actual displacement; and determine the sum of the preset step size and the difference value as the preset step size for the next movement of the workpiece table.

Wherein, before the control unit 7 controls the drive motor 5 to drive the workpiece table 1 to move in the X direction with the second preset step size, the control unit 7 controls the drive motor 5 to drive the workpiece table 1 to move along the X direction with the first preset step size, The displacement measuring unit 6 measures the actual displacement of the workpiece table 1 along the X direction, and calculates the difference between the first preset step and the actual displacement, and sums the difference and the first preset step, The value is determined as the second preset step size, and then the control unit 7 controls the drive motor 5 to drive the workpiece table 1 to move along the X direction with the second preset step size.

The preset step size may be determined according to factors such as scanning distance, camera pixel size, camera pixel number, and reserved amount.

For example, if the first preset step size is 10 μm, and the actual displacement of the workpiece table 1 is 9 μm, then the second preset step size is 11 μm, to avoid the movement position error of the workpiece table 1 caused by mechanical disturbance. The worse the movement of the component stage 1 is, the bigger it is, so that the image elements of the measured object formed by the time-delay integral camera are more and more blurred.

The light source 2 may be a highly uniform and highly stable light source, so that the time-delay integrator camera 4 can prevent the detection beam 201 emitted from the light source 2 from affecting the imaging during imaging. The control unit 7 may be a computer. The drive unit 5 may be a drive motor.

Optionally, the optical imaging unit 3 includes a first optical lens 31 and a second optical lens 32, the first optical lens 31 is located on the side of the object to be measured 8 away from the workpiece table 1, and the second optical lens 32 is located on the first optical lens 31. On the side facing away from the workpiece table 1 , the first optical lens 31 is used to collect and collimate the light beam 202 to be imaged, and the light beam 202 to be imaged passes through the second optical lens 32 and converges on the time-lapse camera 4 .

The first optical lens 31 may be a collimating lens, and the second optical lens 32 may be a converging lens (convex lens). It can be understood that the first optical lens 31 can be a lens or a group of lenses, and similarly, the second optical lens 32 can also be a lens or a group of lenses, which can be selected according to actual conditions. The first optical lens 31 and the second optical lens 32 can be installed in the same lens barrel, which is beneficial to prevent the optical imaging unit 3 from being disturbed by the external environment, and is further beneficial to the detector of the time-delay integrator 4 to sense all the beams to be imaged. 202 , so that the acquired image of the object to be tested carries all the defect information of the object to be tested 8 .

Optionally, the displacement measuring unit 6 may be a laser interferometer or a grating ruler.

Taking the laser interferometer as an example, as shown in Figure 2, the single-frequency laser interferometer measurement uses the Michelson interference principle, that is, after the laser beam (circularly polarized light) emitted from the laser interferometer host 9 passes through the beam splitter 10, It is divided into a first laser beam 13 (linearly polarized light) and a second laser beam 14 (linearly polarized light); the two laser beams are reflected by the cube mirror 11 and the cube mirror 12 respectively, and then return parallel to the outgoing light, and pass through the beam splitter. After 10, superposition is carried out. Since the two laser beams have the same frequency, the same vibration direction and a constant phase difference, the interference conditions are satisfied; every time the cube mirror 11 moves half the distance of the laser wavelength, a complete light-dark interference phenomenon (fringes) will be generated. Change one cycle, bright stripes become dark stripes, dark stripes become bright stripes). The measurement distance is equal to the number of interference fringes multiplied by the half wavelength of the laser; by using the subdivision method, the fringe variation ΔN can be accurately obtained, and the moving measurement distance ΔL of the workpiece table 1 is equal to the number of interference fringes ΔN multiplied by the half wavelength of the laser λ/2. which is

It can be understood that the pyramid mirror 11 can be installed on the side surface of the workpiece table 1 along the push-broom direction of the time-delay integrator camera 4 to accurately measure the actual displacement of the workpiece table 1 when the workpiece table 1 moves along the push-broom direction.

It should be noted that the standard DUT image element is obtained by the deconvolution operation between the measured DUT image element and the response function, wherein the acquisition of the response function is related to the preset step size, and the preset step size and response can be obtained through experiments. The preset corresponding relationship of the function: in the laboratory, the defect detection device shown in FIG. 1 is still used, the standard defect test object is selected as the test object 8, and the standard defect test object is flat. The actual displacement of the workpiece table 1 is the same as the preset step size. That is to say, when the control unit 7 controls the workpiece table 1 to move in the push-broom direction of the time-delay integrator camera 4 with a preset step size, the actual displacement of the workpiece table 1 is the preset step size, so that the time-delay integrator camera 4 moves 4 The image element of the object to be tested obtained each time is the image element of the standard object to be tested, and the image element of the standard object to be tested is used as the response function corresponding to the preset step size, and so on, until the time delay integral camera 4 scans the image element. For the entire test object, obtain the corresponding relationship between the preset step size and the response function.

Further, the corresponding relationship between the preset step size and the response function calibrated in the laboratory is pre-stored in the control unit 7 in advance, and in the actual measurement process, the response function is obtained according to the preset step size, and is inversely measured with the image element of the object to be tested. Convolution operation, and finally obtain a clear image of the standard object to be tested.

It can be understood that in the actual measurement process, the preset step size for controlling the next movement of the workpiece table 1 may be different from that of the laboratory calibration. An example of the process of determining the response function according to the preset step size is as follows: In the laboratory, every interval 10μm (that is, the preset step size) to obtain a standard image element of the object to be tested. During the actual measurement process, the workpiece table 1 is controlled to move at 10 μm for the first time. When the actual displacement of the workpiece table 1 is 9 μm, the second time is 11 μm. Control the movement of the workpiece stage 1, then, the response function selected for the second time is the image element of the standard object to be tested at 20 μm.

Based on the same inventive concept, another embodiment of the present invention further provides a defect detection method. FIG. 3 is a flowchart of a defect detection method proposed by an embodiment of the present invention. As shown in Figure 3, it includes the following steps:

S1, control the workpiece table to move along the push-broom direction of the time-delay integral camera with a preset step size;

S2, obtain the actual displacement of the workpiece table;

S3, acquiring the image element of the measured object to be measured formed by the time-delay integral camera;

S4, according to the measured image element of the object to be measured and the preset step size, obtain the image element of the standard object to be measured;

S5, determining the preset step size of the next movement of the workpiece table according to the preset step size and the actual displacement;

Repeat the above steps in turn, until the time-delay integrator scans the object to be tested to obtain a plurality of image elements of the standard object to be tested;

S6, splicing a plurality of standard object to be tested image elements in turn to form a standard object to be tested image;

S7, perform defect detection on the object to be tested according to the standard image of the object to be tested.

Optionally, as shown in Figure 4, S4 includes:

S41, determining the response function of the measured object image element according to the preset step size;

S42 , according to the response function and the actually measured image element of the object to be measured, determine the image element of the standard object to be measured.

Optionally, as shown in FIG. 5 , S42 includes: using a deconvolution operation to determine a standard object to be measured image element according to the response function and the measured image element of the object to be measured.

Optionally, as shown in Figure 6, S5 includes:

S51, obtain the difference between the preset step size and the actual displacement;

S52, determining the sum of the preset step size and the difference value as the preset step size for the next movement of the workpiece table.

To sum up, according to the defect detection device and method provided by the embodiments of the present invention, the workpiece table is driven to move in the push-broom direction of the time-delay integral camera by controlling the drive motor. Every time the workpiece table moves according to the preset step length, the time-delay integral camera obtains an image element of the object to be measured; every time the workpiece table moves according to the preset step size, the displacement measuring unit measures the time delay integral along the workpiece table once. The actual displacement of the camera in the push-broom direction; the control unit is used to obtain the standard object image element according to the actual measured object image element and the preset step size, and adjust the workpiece table according to the current actual displacement The preset step size of the next movement, until the time-delay integrator completes scanning the object to be tested to obtain a plurality of image elements of the standard object to be tested; splicing a plurality of image elements of the standard object to be tested in sequence, A standard test object image is formed; and defect detection is performed on the test object according to the standard test object image, so that the standard test object image is clearer and the defects of the test object are better identified.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (10)

1. A defect detection apparatus, comprising:

the workpiece table is used for bearing an object to be tested;

the light source is used for emitting a detection light beam, the detection light beam irradiates the object to be detected, and the object to be detected is reflected or scattered to form a light beam to be imaged;

the optical imaging unit is positioned on the transmission path of the light beam to be imaged and used for collecting the light beam to be imaged;

the time delay integral camera is positioned on one side of the optical imaging unit, which is far away from the object to be detected;

the driving unit is used for driving the workpiece table to move along the push-broom direction of the time delay integral camera according to a preset step length, wherein the time delay integral camera acquires an actually measured object image element every time the workpiece table moves once according to the preset step length;

the displacement measuring unit measures the actual displacement of the workpiece table along the push-sweeping direction of the time delay integral camera once when the workpiece table moves once according to the preset step length;

the control unit is respectively electrically connected with the time delay integral camera, the displacement measuring unit and the driving unit and is used for acquiring a standard object image element according to the actually measured object image element and the preset step length, and adjusting the preset step length of the next movement of the workpiece platform according to the actual displacement of the current time until the time delay integral camera scans the object to be detected to finish acquiring a plurality of standard object image elements; sequentially splicing a plurality of standard object image elements to form a standard object image; and detecting the defect of the object to be detected according to the standard object image to be detected.

2. The apparatus according to claim 1, wherein the control unit is further configured to determine a response function of the measured object image element according to the preset step length; and determining the standard object image element to be detected according to the response function and the actually measured object image element to be detected.

3. The apparatus of claim 2, wherein the control unit is further configured to determine the standard test object image elements from the response function and the measured test object image elements using a deconvolution operation.

4. The defect detection apparatus of claim 1, wherein the control unit is further configured to obtain a difference between the preset step length and the actual displacement; and determining the sum of the preset step length and the difference value as the preset step length of the next movement of the workpiece table.

5. The apparatus of claim 1, wherein the optical imaging unit includes a first optical lens and a second optical lens, the first optical lens is located on a side of the object to be measured away from the stage, the second optical lens is located on a side of the first optical lens away from the stage, the first optical lens is configured to collect and collimate the light beam to be imaged, and the light beam to be imaged passes through the second optical lens and is converged by the time delay integrator camera.

6. The apparatus of claim 1, wherein the displacement measuring unit is a laser interferometer or a grating scale.

7. A defect detection method implemented based on the defect detection apparatus of any one of claims 1 to 6, comprising the steps of:

controlling the workpiece table to move along the push-scanning direction of the time delay integral camera by a preset step length;

acquiring the actual displacement of the workpiece table;

acquiring an actually measured object image element to be measured formed by the time delay integral camera;

acquiring a standard object image element to be detected according to the actually measured object image element to be detected and the preset step length;

determining a preset step length of the next movement of the workpiece table according to the preset step length and the actual displacement; repeating the steps in sequence until the time delay integral camera finishes scanning the object to be detected to obtain a plurality of standard object to be detected image elements;

sequentially splicing a plurality of standard object image elements to form a standard object image;

and detecting the defect of the object to be detected according to the standard object image to be detected.

8. The defect detection method of claim 7, wherein the obtaining of the standard object image element according to the actually measured object image element and the preset step length comprises:

determining a response function of the actually measured object image element according to the preset step length;

and determining the standard object image element to be detected according to the response function and the actually measured object image element to be detected.

9. The defect detection method of claim 8, wherein said determining said standard test object image elements from said response function and said measured test object image elements comprises:

and determining the standard object image element to be detected according to the response function and the actually measured object image element to be detected by adopting deconvolution operation.

10. The method of claim 7, wherein the determining the preset step size for the next movement of the workpiece stage according to the preset step size and the actual displacement comprises:

obtaining a difference value between the preset step length and the actual displacement;

and determining the sum of the preset step length and the difference value as the preset step length of the next movement of the workpiece table.

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