TWI866395B - Hybrid trigger method for line scan camera, electronic device and defect inspection system - Google Patents

Abstract

The present invention discloses a hybrid trigger method for line scan camera. The method is conducted by a control device, such that the control device is configured to generate a plurality of first trigger signals and a plurality of second trigger signals based on a specific distance that is detected by an encoder. According to the present invention, the plurality of second trigger signals is inserted between two said first trigger signals. Subsequently, the control device transmits the first trigger signals and the second trigger signals to a line scan camera, such that the line scan camera is triggered to acquire a plurality of image strips from an article, thereby generating a frame of article image that consisting of plurality of image strips. Thus, in case of conducting the hybrid trigger method according to the present invention, the line scan camera is still able to generate a high-resolution article image frame even though the encoder is not a high-resolution encoder.

Description

Hybrid triggering method, control device, and defect detection system for line scan camera

This invention relates to the field of automatic optical inspection (AOI), and in particular to a hybrid triggering method for line scan cameras.

Generally speaking, semi-finished or finished products manufactured using industrial technology must undergo quality inspection to determine whether they meet industrial standards, including cosmetic inspection and functional testing. Therefore, the automated optical inspection (AOI) system using machine vision technology was developed and introduced into the automated production line to replace manpower to perform cosmetic inspection on industrial semi-finished or finished products.

FIG1 is a three-dimensional diagram of a known defect detection system. As shown in FIG1, the defect detection system 1a is used to detect surface defects on a foil 3a transmitted by a roll-to-roll device 2a, and includes at least one line scanning camera 11a, a control device 12a, and an encoder 13a. During normal operation, the encoder 13a monitors the moving distance of the foil 3a and sends an encoder output signal to the control device 12a. It should be understood that by decoding the encoder output signal, the control device 12a can grasp the moving speed (i.e., moving distance) and moving direction of the foil 3a. Then, in accordance with the moving speed of the foil 3a, the control device 12a sends out multiple trigger signals in a time-sharing manner to control the line scanning camera 11a to perform line-by-line image acquisition of the foil 3a to obtain the foil image as shown in FIG2.

It is worth mentioning that in order to ensure the accuracy of defect detection, it is necessary to set the resolution so that a defect has at least 3 pixels in the image. In other words, for a 90μm defect, the resolution must be set at 30μm/pixel. On the other hand, in image processing, it is customary to use the vertical direction as a line and the horizontal direction as a column, so the foil image shown in Figure 2 can be said to be composed of Y image strips, and each image strip has a line width.

As can be seen from the above description, the smaller the line width, the higher the resolution of the foil-like object image. Practical experience shows that the line width is positively correlated with a time interval between the two trigger signals. To be more specific, the time interval refers to the time interval between the i-th trigger signal and the i+1-th trigger signal sent to the line scan camera 11a, i=0~Y-1, and i and Y are both positive integers. For example, after receiving the i-th trigger signal, the line scan camera 11a is triggered to capture an i-th image strip from the foil-like object 3a. In other words, the accuracy of the encoder 13a is positively correlated with the shortest movement distance of the foil-like object 3a that can be monitored, that is, positively correlated with the time interval between the two trigger signals, and the line width is positively correlated with the time interval between the two trigger signals. Therefore, the relationship between the resolution and the encoder accuracy can be expressed by the following formula (i):

In the above formula (i), C is the circumference of the encoder 13a's wheel, and P is the accuracy of the encoder 13a, which is expressed as the number of pulses generated by the encoder 13a during one rotation of the wheel (i.e., the number of pulses contained in one frame of the encoder output signal).

From equation (1) and equation (2), it can be seen that the smaller the circumference of the rice wheel, the higher the resolution of the defect detection system 1a (e.g., 50μm/pixel→30μm/pixel). However, practical experience shows that the encoder 13a with a rice wheel is too small to be installed on the roll-to-roll device 2a. On the other hand, from equation (1) and equation (2), it can also be seen that the resolution of the defect detection system 1a can be improved by increasing the accuracy of the encoder 13a. However, in practice, a high-precision encoder 13a is inevitably accompanied by an expensive price.

In summary, the triggering method of the conventional line scan camera has the problem of limited resolution. In view of this, the inventor of this case has made great efforts to study and invent, and finally developed and completed the hybrid triggering method of the line scan camera of this invention.

The main purpose of the present invention is to provide a hybrid triggering method, which is executed by a control device, thereby generating a plurality of first triggering signals and a plurality of second triggering signals according to a detection distance of an encoder to control a line scan camera to capture a plurality of image strips from an object to form an object image, wherein the plurality of second triggering signals are inserted between any two of the first triggering signals. In this way, when the hybrid triggering method of the present invention is applied, even if a low-precision encoder is used, the line scan camera can be triggered to generate a high-resolution object image.

To achieve the above-mentioned purpose, the present invention proposes an embodiment of the hybrid triggering method, which is executed by a control device, wherein the control device is integrated into a defect detection system including at least one line scan camera and an encoder, and the line scan camera is controlled by the control device to capture a plurality of image strips from an object to form an object image; the hybrid triggering method includes the following steps: receiving an encoder output signal from the encoder, and generating a plurality of first time-sharing triggering signals for the line scan camera according to the encoder output signal; Trigger signal; wherein there is a first time interval between any two of the first trigger signals; a second time interval is calculated according to the width of the image strip, the first time interval and a detection distance of the encoder; and a plurality of second trigger signals are generated for time-sharing triggering the line scan camera, wherein the plurality of second trigger signals are inserted between any two of the first trigger signals, two of the second trigger signals have the second time interval, and there is a third time interval between the second trigger signal and the first trigger signal.

In one embodiment, the control device calculates the second time interval using the following equations (1) and (2):

Wherein, D is the detection distance, t _{IN 1} is the first time interval, t _{IN 2} is the second time interval, V is the rate, and R is the width of the image strip.

In one embodiment, the object is a foil-like object conveyed by a roll-to-roll device, and the foil-like object is any one selected from the group consisting of metal foil, flexible substrate, paper, and flexible substrate covered with an outer layer.

In one embodiment, the control device is any one selected from the group consisting of a circuit board assembly, an electronic device, a laptop computer, a desktop computer, an industrial computer, a tablet computer, and a smart phone.

The present invention also provides an embodiment of a control device for integration into a defect detection system including at least one line scan camera and an encoder; the control device is configured to execute a hybrid triggering method to generate a plurality of first triggering signals and a plurality of second triggering signals for controlling the line scan camera to capture a plurality of image strips from an object to form an object image, and the hybrid triggering method includes the following steps: receiving an encoder output signal from the encoder, and generating a time-sharing triggering signal for the line scan camera according to the encoder output signal; A plurality of the first trigger signals of the camera; wherein there is a first time interval between any two of the first trigger signals; a second time interval is calculated according to the width of the image strip, the first time interval and a detection distance of the encoder; and a plurality of the second trigger signals for time-sharing triggering the line scan camera are generated, wherein the plurality of the second trigger signals are inserted between any two of the first trigger signals, the two second trigger signals have the second time interval, and there is a third time interval between the second trigger signal and the first trigger signal.

In one embodiment, the control device is any one selected from the group consisting of a circuit board assembly, an electronic device, a laptop computer, a desktop computer, an industrial computer, a tablet computer, and a smart phone.

In one embodiment, the control device includes a processor and a memory, the memory stores an application including a plurality of subroutines, and the plurality of subroutines include: a first subroutine, wherein the processor accesses the memory to execute the first subroutine, thereby decoding the encoder output signal to obtain the detection distance; and a second subroutine, wherein the processor accesses the memory to execute the second subroutine, thereby executing the hybrid triggering method.

In one embodiment, the processor calculates the second time interval using the following equations (1) and (2):

Wherein, D is the detection distance, t _{IN 1} is the first time interval, t _{IN 2} is the second time interval, V is the rate, and R is the width of the image strip.

In one embodiment, the object is a foil-like object conveyed by a roll-to-roll device, and the foil-like object is any one selected from the group consisting of metal foil, flexible substrate, paper, and flexible substrate covered with an outer layer.

Furthermore, the present invention also provides an embodiment of a defect detection system, which is used to detect surface defects on a foil-like object transmitted by a roll-to-roll device, and is characterized in that the defect detection system includes at least one line scan camera, an encoder, and the control device of the present invention as described above.

1a: Defect detection system

11a: Line scan camera

12a: Control device

13a: Encoder

2a: Roll-to-roll equipment

3a: Foil

1: Defect detection system

11: Line scan camera

12: Control device

12P: Processor

12M: Memory

12M1: decoding unit

12M2: Hybrid trigger unit

13: Encoder

2: Roll-to-roll equipment

3: Foil

S1~S3: Steps

TS1: First trigger signal

TS2: Second trigger signal

FIG. 1 is a three-dimensional diagram of a known defect detection system; FIG. 2 is an image of a foil-like object captured by driving the line scan camera shown in FIG. 1; FIG. 3 is a three-dimensional diagram of a defect detection system of the present invention; FIG. 4 is a block diagram of the defect detection system of the present invention; FIG. 5 is an image of a foil-like object captured by driving the line scan camera shown in FIG. 3; FIG. 6 is a flow chart of a hybrid triggering method of the present invention; FIG. 7A is a first schematic timing diagram of a plurality of first trigger signals and a plurality of second trigger signals; and FIG. 7B is a second schematic timing diagram of a plurality of first trigger signals and a plurality of second trigger signals.

In order to more clearly describe the hybrid triggering method, control device, and defect detection system of a line scan camera of the present invention, the following will be accompanied by drawings to explain in detail the preferred embodiment of the present invention.

FIG. 3 is a perspective view of a defect detection system of the present invention, and FIG. 4 is a block diagram of the defect detection system of the present invention. As shown in Figures 3 and 4, the defect detection system 1 is used to detect surface defects on a foil 3 transported by a roll-to-roll device 2, and includes at least one line scan camera 11 and an encoder. (encoder) 12, and a control device 12. In a feasible embodiment, the foil 3 may be, but is not limited to, a metal foil, a flexible substrate, paper, or a flexible substrate covered with an outer layer. Furthermore, the control device 12 may be, but is not limited to, a circuit board assembly, an electronic device, a notebook computer, a desktop computer, an industrial computer, a tablet computer, or a smart phone.

Specifically, the control device 12 includes a processor 12P and a memory 12M, and the memory 12M stores an application program including a plurality of subroutines. As shown in FIG4 , the plurality of subroutines include: a first subroutines presented by a decoding unit 12M1 and a second subroutines presented by a mixing trigger unit 12M2. When working normally, the encoder 13 monitors the moving distance of the foil-like object 3 transmitted by the roll-to-roll device 2 and sends an encoder output signal to the processor 12P. Thereafter, the processor 12P accesses the memory 12M to execute the first subroutine (i.e., the decoding unit 12M1), thereby decoding the encoder output signal to obtain a detection distance (i.e., the moving distance of the foil-like object 3). Then, in accordance with the moving speed (i.e., moving distance) of the foil-like object 3 and the accuracy of the encoder 13, the control device 12 accesses the memory 12M to execute the second subroutine, thereby executing a hybrid triggering method of the present invention, thereby generating a plurality of first triggering signals and a plurality of second triggering signals for controlling the line scan camera 11 to capture a plurality of image strips from the foil-like object 3 to form an object image (as shown in FIG. 5 ).

FIG6 is a flow chart of a hybrid triggering method of the present invention. As shown in FIG6, the method flow first executes step S1: receiving an encoder output signal from the encoder 13, and generating a plurality of first trigger signals for time-sharing triggering the line scan camera 11 according to the encoder output signal. FIG7A is a first schematic timing diagram of a plurality of first trigger signals and a plurality of second trigger signals. As shown in FIG7A, after decoding the encoder output signal, the processor 12P obtains a detection distance (i.e., moving distance) of the foil-like object 3. Next, according to the accuracy of the encoder 13a and the detection distance, the processor 12P can generate a plurality of first trigger signals TS1, and any two of the first trigger signals TS1 have a first time interval t _{IN 1} .

It should be understood that the first time interval t _{IN 1} refers to the time interval between the i-th first trigger signal TS1 and the i+1-th first trigger signal TS1 sent to the line scan camera 11a, i=0~Y-1 (i.e., row Y shown in FIG. 5 ). For example, after receiving the i-th first trigger signal TS1, the line scan camera 11 is triggered to capture an i-th image strip from the foil-like object 3. Therefore, the accuracy of the encoder 13 is positively correlated with the shortest moving distance of the foil-like object 3 that can be monitored (i.e., the shortest detection distance), that is, positively correlated with the time interval between the two first trigger signals TS1 (i.e., the), and the line width is positively correlated with the first time interval between the two first trigger signals TS1. Therefore, the minimum value of the line width is limited by the accuracy of the encoder and/or the circumference of its meter wheel.

Continuing, as shown in FIG6 , the method flow then executes step S2: a second time interval is calculated according to the width of the image strip, the first time interval and a detection distance of the encoder 13. Then, the method flow executes step S3: a plurality of second trigger signals TS2 are generated for time-sharing triggering the line scan camera 11. Specifically, the processor 12P calculates the second time interval t _{IN 2} using the following equations (1) and (2):

In the above formula (1) and formula (2), D is the detection distance, t _{IN 1} is the first time interval, t _{IN 2} is the second time interval, V is the speed, and R is the width of the image strip. As shown in FIG7 , after calculating the second time interval t _{IN 2} , the processor 12P can then generate a plurality of second trigger signals TS2 for time-sharing triggering the line scan camera 11, wherein the plurality of second trigger signals TS2 are inserted between any two of the first trigger signals TS1, the two second trigger signals TS2 have the second time interval t _{IN 2} , and the second trigger signal TS2 and the first trigger signal TS1 have a third time interval t _{IN 3} . Thus, the processor 12P sends a plurality of first trigger signals TS1 and a plurality of second trigger signals TS2 to the line scan camera 11, thereby controlling the line scan camera 11 to capture Y image strips from the foil 3 to form a foil image as shown in FIG5 . Moreover, from the above formula (2), it can be seen that the line width of each image strip is R= t _{IN 2} /V. In other words, the resolution of the foil image is no longer directly related to the accuracy of the encoder 13 and/or the circumference of the meter wheel.

FIG7B is a second schematic timing diagram of a plurality of first trigger signals and a plurality of second trigger signals. Comparing FIG7A with FIG7B, it can be seen that the first time interval t _{IN 1} in FIG7B becomes longer, which can be understood as the original encoder 13 is replaced by another one with lower precision. Since t _{IN 1} and D are known, when the target line width (i.e., R value) of the image strip is determined, the processor 12P calculates the second time interval t _{IN 2} using the above formulas (1) and (2), and then generates a plurality of second trigger signals TS2 for time-sharing triggering the line scan camera 11.

In summary, even if the defect detection system 1 uses a low-precision encoder 13, which results in a limit on the minimum line width of the image strip, the control device 12 can generate a plurality of second trigger signals TS2 inserted between two first trigger signals TS1 when the hybrid trigger method of the present invention is applied, thereby further shortening the line width of the image strip, thereby improving the resolution of the foil image containing Y image strips. In other words, when the hybrid trigger method of the present invention is applied, the defect detection system 1 is allowed to be used with a low-precision, cheap encoder, without the need for a high-precision, expensive encoder.

Thus, the above has completely and clearly described the hybrid triggering method, control device, and defect detection system of a line scan camera proposed by the present invention. It must be emphasized that the above detailed description is a specific description of the feasible implementation example of the present invention, but the implementation example is not used to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the technical spirit of the invention should be included in the patent scope of this case.

S1~S3: Steps

Claims (10)

A hybrid triggering method is performed by a control device, wherein the control device is integrated into a defect detection system including at least one line scan camera and an encoder, and the line scan camera is controlled by the control device to capture a plurality of image strips from an object to form an object image; the hybrid triggering method includes the following steps: Receiving an encoder output signal from the encoder, and generating a plurality of first triggering signals for time-sharing triggering the line scan camera according to the encoder output signal; wherein there is a first time interval between any two of the first triggering signals; Calculating a second time interval according to the width of the image strip, the first time interval and a detection distance of the encoder; and Generate a plurality of second trigger signals for time-sharing triggering the line scan camera, wherein the plurality of second trigger signals are inserted between any two of the first trigger signals, the two second trigger signals have the second time interval, and there is a third time interval between the second trigger signal and the first trigger signal. The hybrid triggering method as described in claim 1, wherein the control device calculates the second time interval using the following equations (1) and (2): ···································(1); ································ (2); wherein D is the detection distance, is the first time interval, is the second time interval, V is the rate, and R is the width of the image strip. A hybrid triggering method as described in claim 1, wherein the object is a foil-like object conveyed by a roll-to-roll device, and the foil-like object is any one selected from the group consisting of metal foil, a flexible substrate, paper, and a flexible substrate covered with an outer layer. The hybrid triggering method as described in claim 1, wherein the control device is any one selected from the group consisting of a circuit board assembly, an electronic device, a laptop computer, a desktop computer, an industrial computer, a tablet computer, and a smart phone. A control device for integration into a defect detection system including at least one line scan camera and an encoder; the control device is configured to execute a hybrid triggering method, thereby generating a plurality of first triggering signals and a plurality of second triggering signals for controlling the line scan camera to capture a plurality of image strips from an object to form an object image, and the hybrid triggering method comprises the following steps: Receiving an encoder output signal from the encoder, and generating a plurality of the first triggering signals for time-sharing triggering the line scan camera according to the encoder output signal; wherein there is a first time interval between any two of the first triggering signals; A second time interval is calculated according to the width of the image strip, the first time interval and a detection distance of the encoder; and A plurality of the second trigger signals are generated for time-sharing triggering the line scan camera, wherein the plurality of second trigger signals are inserted between any two of the first trigger signals, the two second trigger signals have the second time interval, and there is a third time interval between the second trigger signal and the first trigger signal. The control device as described in claim 5, wherein the control device is any one selected from the group consisting of a circuit board assembly, an electronic device, a laptop computer, a desktop computer, an industrial computer, a tablet computer, and a smart phone. A control device as described in claim 5, wherein the control device includes a processor and a memory, the memory stores an application including a plurality of subroutines, and the plurality of subroutines include: a first subroutine, wherein the processor accesses the memory to execute the first subroutine, thereby decoding the encoder output signal to obtain the detection distance; and a second subroutine, wherein the processor accesses the memory to execute the second subroutine, thereby executing the hybrid triggering method. The control device as claimed in claim 7, wherein the processor calculates the second time interval using the following equations (1) and (2): ···································(1); ································ (2); wherein D is the detection distance, is the first time interval, is the second time interval, V is the rate, and R is the width of the image strip. A control device as described in claim 5, wherein the object is a foil-like object conveyed by a roll-to-roll device, and the foil-like object is any one selected from the group consisting of metal foil, a flexible substrate, paper, and a flexible substrate covered with an outer layer. A defect detection system for detecting surface defects on a foil-like object conveyed by a roll-to-roll device, characterized in that the defect detection system comprises at least one line scan camera, an encoder and a control device as described in any one of claim 5 to claim 9.