CN110376207A - A kind of ultra-wide slab surface defect on-line detecting system image-pickup method - Google Patents

A kind of ultra-wide slab surface defect on-line detecting system image-pickup method Download PDF

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Publication number
CN110376207A
CN110376207A CN201910647988.3A CN201910647988A CN110376207A CN 110376207 A CN110376207 A CN 110376207A CN 201910647988 A CN201910647988 A CN 201910647988A CN 110376207 A CN110376207 A CN 110376207A
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China
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line
image
ultra
camera
digital camera
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CN201910647988.3A
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Chinese (zh)
Inventor
杨朝霖
徐科
邓能辉
周鹏
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北京科技大学
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Priority to CN201910647988.3A priority Critical patent/CN110376207A/en
Publication of CN110376207A publication Critical patent/CN110376207A/en

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using infra-red, visible or ultra-violet light
    • G01N21/84Systems specially adapted for particular applications
    • G01N21/88Investigating the presence of flaws or contamination
    • G01N21/8851Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using infra-red, visible or ultra-violet light
    • G01N21/84Systems specially adapted for particular applications
    • G01N21/88Investigating the presence of flaws or contamination
    • G01N21/8851Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • G01N2021/8887Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques

Abstract

The present invention provides a kind of ultra-wide slab surface defect on-line detecting system image-pickup method, belongs to machine vision technical field of nondestructive testing.This method determines the line-scan digital camera quantity used according to the maximum width of plate face and the minimum dimension and camera resolution of required detection defect, and narrow-band LED quantity of light source and camera quantity are consistent.After steel plate enters camera pickup area, laser velocimeter obtains steel plate speed, to determine the acquisition line rate of line-scan digital camera.Then multichannel PWM signal generator is controlled by industrial personal computer, generate pwm signal identical with acquisition line rate with pulse frequency, it exports pwm signal identical with camera quantity and controls camera synchronous acquisition, the image that each camera acquires is obtained full surface image in the displacement splicing of length and width direction by final realize.This method can realize the quick adjustment to light-source brightness in the case where guaranteeing that camera acquisition rate does not change, and guarantee the uniform of image background brightness.

Description

A kind of ultra-wide slab surface defect on-line detecting system image-pickup method

Technical field

The present invention relates to machine vision technical field of nondestructive testing, particularly relates to a kind of ultra-wide slab surface defect and examine online Examining system image-pickup method.

Background technique

It is obtained on the production line of major steel mill currently based on the Surface Defects in Steel Plate on-line detecting system of machine vision It is widely used, to guaranteeing that it is critical that plate surface quality plays the role of, the key of the system is that background to be collected is uniform Complete steel plate image just can be carried out accurate defect recognition.For being greater than the detection of the plank of 5 meters or more ultra-wide, due to detection The requirement of precision needs to arrange the acquisition that multiple cameras could complete entire plate face in the direction of the width, these multiple cameras acquisitions The needs of image, which carry out accurately splicing in width direction and the direction of motion, can just be convenient for subsequent defect analysis, due to plate Face is very wide, and a banded LED light source cannot be guaranteed the uniformity in entire illumination region, will lead to the steel plate collected Image background brightness shows non-uniform situation in the direction of the width, so need a plurality of band-like LED light source to provide illumination, How these LED light source brightness changes are controlled in time to guarantee that camera corresponding with light source collects the uniform image needs of background Emphasis considers.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of ultra-wide slab surface defect on-line detecting system Image Acquisition Method.

This method is increased by line-scan digital camera and narrow-band LED light source, multichannel PWM signal generator, laser velocimeter, signal The combination of strong module realizes that Image Acquisition, realization process comprise the following steps that

(1) according to the minimum dimension α and line-scan digital camera point of the maximum width L of ultra-wide slab plate face and required detection defect Resolution M, determines the line-scan digital camera quantity N used, and the quantity and line-scan digital camera quantity of narrow-band LED light source are consistent;

(2) after ultra-wide slab enters line-scan digital camera pickup area, laser testing instrument obtains ultra-wide slab speed ν, according to obtaining The ultra-wide slab speed ν that gets and need to detect the minimum dimension α of defect to determine the acquisition line rate f of line-scan digital camera;

(3) multichannel PWM signal generator is controlled, pulse frequency pwm signal identical with acquisition line rate f is generated, it is defeated The road N identical with line-scan digital camera quantity pulse signal out, every road signal are divided into two parts;

(4) by calibrating the position difference between each light belt of narrow-band LED light source in advance, each line-scan digital camera is acquired The image to get off uses displacement splicing in length direction;

(5) image that each line-scan digital camera acquires is obtained into full surface image in the displacement splicing of length and width direction.

Wherein, line-scan digital camera quantity N=2L/ (α × M) in step (1).

Acquisition line rate f=2 ν/α of line-scan digital camera in step (2), to guarantee that minimum dimension is the detection of α defect, here Acquisition precision needs to reach α/2.

A portion of step (3) road Zhong Mei signal is sent to be synchronized using the line-scan digital camera realization of external trigger mode and be adopted Collection, another part pass through the power supply after the enhancing of signal enhancing module directly as narrow-band LED light source.It is supplied as narrow-band LED light source Electricity signal can guarantee acquisition rate it is constant i.e. acquisition precision is constant in the case where, by control PWM signal generator more Change signal dutyfactor and realizes light-source brightness adjustment to realize the adjustment of camera acquisition brightness of image.

The acquisition illumination region of each group line-scan digital camera uses interlaced mode arrangement.

Step (4) specifically: the illumination region dislocation distance of two adjacent linear array camera is σ, ultra-wide slab length direction Upper acquisition precision θ is α/2, and α is the minimum dimension for needing to detect defect, then the pixel quantity Δ for needing to shift are as follows:

Δ=σ/θ=2 σ/α.

The advantageous effects of the above technical solutions of the present invention are as follows:

In above scheme, using multiple groups line-scan digital camera and narrow-band LED light source, steel plate is obtained by laser velocimeter and is accurately transported Dynamic speed realizes the carry out external trigger synchronous acquisition control to multiple cameras using pwm signal, guarantees multiple camera acquisitions position It sets, while controlling the brightness of the every a line lighting source of Image Acquisition by the pulse width using same signal, this method can To realize that the light-source brightness of each line to acquisition image adjusts, while being realized pair using same pwm signal hardware mode The control of speed and brightness of image is acquired, it can be achieved that single line brightness adjustment in image, allows light source quick response brightness change Request.

Detailed description of the invention

Fig. 1 is ultra-wide slab surface defect on-line detecting system image-pickup method overall plan figure of the invention;

Fig. 2 is each camera pickup area layout in the embodiment of the present invention;

Fig. 3 is pwm signal schematic diagram in the embodiment of the present invention.

Specific embodiment

To keep the technical problem to be solved in the present invention, technical solution and advantage clearer, below in conjunction with attached drawing and tool Body embodiment is described in detail.

The present invention provides a kind of ultra-wide slab surface defect on-line detecting system image-pickup method.

As shown in Figure 1, this method passes through line-scan digital camera and narrow-band LED light source, multichannel PWM signal generator, Laser Measuring The combination of fast instrument, signal enhancing module realizes that Image Acquisition, realization process comprise the following steps that

(1) according to the maximum width L of ultra-wide slab plate face and the minimum dimension α and line-scan digital camera point that need to detect defect Resolution M, determines the line-scan digital camera quantity N used, and the quantity and line-scan digital camera quantity of narrow-band LED light source are consistent;

(2) after ultra-wide slab enters line-scan digital camera pickup area, laser testing instrument obtains ultra-wide slab speed ν, according to obtaining The ultra-wide slab speed ν that gets and need to detect the minimum dimension α of defect to determine the acquisition line rate f of line-scan digital camera;

(3) multichannel PWM signal generator is controlled, pulse frequency pwm signal identical with acquisition line rate f is generated, it is defeated The road N identical with line-scan digital camera quantity pulse signal out, every road signal are divided into two parts;

(4) by calibrating the position difference between each light belt of narrow-band LED light source in advance, each line-scan digital camera is acquired The image to get off uses displacement splicing in length direction;

(5) image that each line-scan digital camera acquires is obtained into full surface image in the displacement splicing of length and width direction.

It is explained combined with specific embodiments below.

According to the minimum dimension α of the maximum width L of plate face and required detection defect, and the pixel of used line-scan digital camera Quantity M determines to need camera quantity N=2L/ (α M) to be used in width direction;

Meanwhile the quantity of narrow-band LED light source is identical with camera quantity.

Linear array is determined according to the minimum dimension α for needing to detect defect on the steel plate speed ν and width direction got Acquisition line rate f, f=2 ν/α of camera.

As shown in figure 3, controlling multichannel PWM signal generator using the acquisition line rate f got, generates and acquire The road the N pwm signal of line rate identical pulse frequency, every road signal are divided into two parts, and a part is sent to using external trigger mode Line-scan digital camera, can guarantee the synchronous acquisition of N number of camera in this way, realize and guarantee consistent inspection in steel plate width and length direction Survey precision, the periodic quantity t of the signal are as follows:

T=1/f

Confession of another part pwm signal after signal intensifier circuit amplifies as narrow-band LED light source matched with camera Electricity, by calculating a line of the acquisition of each camera or the average gray value of multirow in real time, assessing the average gray value and setting Determine the difference of benchmark gray scale, send the instruction of adjustment pwm signal pulse width, adjust the pulsewidth λ value of pwm signal, it is believed that There are the relationships of near-linear for the variation of the brightness ν and pulsewidth λ of light source.

ν=K λ+β

K is a positive constant, and β is a constant.

Thus guaranteeing the constant situation of pwm signal pulse frequency, that is to say, that guarantee the acquisition rate of all cameras All identical situation, pwm value, that is, pwm signal duty ratio by changing the pwm signal powered to LED light source can change The brightness of changing light, realizes the adjustment to each camera acquisition image background brightness, and the entire process that adjusts can use self feed back Mode carry out, realize quickly adjustment light-source brightness purpose.

Acquisition and the brightness of illumination of each camera for controlling all cameras by one group of pwm signal in this way, guarantee image Splicing precision and background it is uniform.

To avoid the lighting source of each camera from influencing each other, the acquisition illumination region of each group camera is using interlaced Mode, as shown in Figure 2, it is ensured that the influence for avoiding mutual light source to a certain extent, since entire collection process is according to speed Precision in the accurate control direction of motion of degree is adopted each camera by calibrating the position difference between each light belt in advance For the image collected in length direction using displacement splicing, such as illumination region dislocation distance of two neighboring camera is σ, steel Acquisition precision θ is α/2 on plate length direction, and α is the minimum dimension for needing to detect defect, the then pixel quantity for needing to shift here Δ is Δ=σ/θ=2 σ/α.

In the specific application process, workflow step is as follows:

Step 1: the steel plate in movement enters the pickup area of camera, (camera be may be implemented using line-scan digital camera in steel plate Image in movement accurately splices, and pickup area is very narrow, can be to avoid the interference of different cameral light source), laser velocimeter Measurement obtains the accurate motion speed when front spring.

Step 2:, when front spring movement velocity, calculating the acquisition linear speed that camera needs to use according to design acquisition precision Rate, control multichannel PWM signal generator generate the multi-channel PWM pulse signal identical with camera quantity of same frequency, every road letter Number a part is transmitted directly to line-scan digital camera, and another part is enhanced by signal power to be supplied after module is amplified to LED light source Electricity, camera will start synchronous acquisition after receiving signal by the way of external trigger.

Step 3: the single line or multi-thread average gray value that are collected by calculating each camera, the benchmark with setting It is compared, if difference value is larger, the pulse width of the road pwm pulse signal is adjusted, is not changing acquisition rate In the case where the brightness of light source is adjusted in time, guarantee obtain each uniform image of camera background luminance,

Step 4: after the image for obtaining each camera, in the direction of the width according to prior overlapping positions obtained by calibrating Image is shifted, splicing obtains the image of whole surface after displacement.

The above is a preferred embodiment of the present invention, it is noted that for those skilled in the art For, without departing from the principles of the present invention, several improvements and modifications can also be made, these improvements and modifications It should be regarded as protection scope of the present invention.

Claims (7)

1. a kind of ultra-wide slab surface defect on-line detecting system image-pickup method, it is characterised in that: this method passes through linear array Ultra-wide is realized in the combination of camera and narrow-band LED light source, multichannel PWM signal generator, laser velocimeter, signal enhancing module Slab Image Acquisition, realization process comprise the following steps that
(1) according to the minimum dimension α and line-scan digital camera resolution ratio of the maximum width L of ultra-wide slab plate face and required detection defect M, determines the line-scan digital camera quantity N used, and the quantity and line-scan digital camera quantity of narrow-band LED light source are consistent;
(2) after ultra-wide slab enters line-scan digital camera pickup area, laser testing instrument obtains ultra-wide slab speed ν, according to getting Ultra-wide slab speed ν and the minimum dimension α of defect need to be detected to determine the acquisition line rate f of line-scan digital camera;
(3) industrial personal computer controls multichannel PWM signal generator, generates pulse frequency pwm signal identical with acquisition line rate f, The road N identical with line-scan digital camera quantity pulse signal is exported, every road signal is divided into two parts;
(4) by calibrating the position difference between each light belt of narrow-band LED light source in advance, each line-scan digital camera is collected Image length direction using displacement splicing;
(5) image that each line-scan digital camera acquires is obtained into full surface image in the displacement splicing of length and width direction.
2. ultra-wide slab surface defect on-line detecting system image-pickup method according to claim 1, it is characterised in that: Line-scan digital camera quantity N=2L/ (α × M) in the step (1).
3. ultra-wide slab surface defect on-line detecting system image-pickup method according to claim 1, it is characterised in that: Acquisition line rate f=2 ν/α of line-scan digital camera in the step (2).
4. ultra-wide slab surface defect on-line detecting system image-pickup method according to claim 1, it is characterised in that: A portion of step (3) road Zhong Mei signal, which is sent to, realizes synchronous acquisition using the line-scan digital camera of external trigger mode, Another part passes through the power supply after the enhancing of signal enhancing module directly as narrow-band LED light source.
5. ultra-wide slab surface defect on-line detecting system image-pickup method according to claim 1, it is characterised in that: The acquisition illumination region of each group line-scan digital camera uses interlaced mode arrangement.
6. ultra-wide slab surface defect on-line detecting system image-pickup method according to claim 1, it is characterised in that: The step (4) specifically: the illumination region dislocation distance of two adjacent linear array camera is σ, to guarantee to detect minimum Defect having a size of α, acquisition precision θ is α/2, then the pixel quantity Δ for needing to shift on ultra-wide slab length direction are as follows:
Δ=σ/θ=2 σ/α.
7. ultra-wide slab surface defect on-line detecting system image-pickup method according to claim 4, it is characterised in that: Enhancing pwm signal as narrow-band LED light source power supply can guarantee acquisition rate it is constant i.e. acquisition precision is constant in the case where, Signal dutyfactor, which is changed, by control PWM signal generator realizes light-source brightness adjustment to realize that camera acquires brightness of image Quickly adjustment.
CN201910647988.3A 2019-07-16 2019-07-16 A kind of ultra-wide slab surface defect on-line detecting system image-pickup method CN110376207A (en)

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