“Detection is one of the important steps in the production of components. In the previous article, the editor introduced infrared detection and light detection. In order to improve everyone’s understanding of detection, this article will introduce CCD detection and oxygen detector.
Detection is one of the important steps in the production of components. In the previous article, the editor introduced infrared detection and light detection. In order to improve everyone’s understanding of detection, this article will introduce CCD detection and oxygen detector.
1. CCD detection
(1) Introduction of CCD vision system
1. The role of CCD vision system
Use machines to replace human eyes to make various measurements and judgments.
2. Composition of CCD vision system
The system integrates technologies in optics, mechanics, electronics, computer software and hardware, and involves many fields such as computer, image processing, pattern recognition, artificial intelligence, signal processing, and opto-mechanical integration. Including digital image processing technology, optical imaging technology, sensor technology, analog and digital video technology, computer software and hardware technology, human-machine interface technology, etc.
3. The composition diagram of the CCD vision system is as follows:
(2) CCD detection principle
This project applies embedded central control and industrial-grade image high-speed transmission control technology, and successfully establishes a photoelectric detection system based on CCD/CMOS and DSP/FPGA image recognition and processing technology. The self-tuning technology of selected parameters of fuzzy control is applied, so that the system has self-adaptive adjustment for accurate detection and realizes the function of automatic sorting of products.
Figure 1 Flowchart of the control system
The photoelectric detection system mainly detects some characteristic parameters (grayscale distribution, RGB score, etc.) of the inspected object, so as to accurately identify the defect information from the object, and carry out the next operation through the subsequent system, which is mainly divided into the following: Part of the CCD/CMOS image acquisition part of the system image data acquisition and processing board The optical signal detection element CCD/CMOS adopts the imported dynamic analysis single-output type, which is suitable for high-precision detection, and ensures the actual data output rate of 320MB/s. Area array CCD /CMOS. The pixels are 4000*3000 and 1600*1200 respectively, and the frame rate reaches 10FPS. Using CCD/CMOS as the input image sensor, the transformation of image information from spatial domain to time domain is realized. In order to ensure the required detection accuracy, a reasonable resolution needs to be determined. According to the size of the tested product, it is preliminarily determined that the system design resolution is 0.2mm pixel. The light intensity signal received by the CCD/CMOS is converted into a voltage amplitude, and after A/D conversion, the DSP/FPGA chip performs signal acquisition, that is, the quantization processing process of the video signal. The image acquisition processing process is shown in the figure:
Figure 2 Image acquisition and processing process
In automatic detection, it is based on the pairing of images using segmentation-based image matching algorithms. The task of image segmentation is to decompose the image into disjoint regions, each of which satisfies the consistency of a specific region and is connected, and different regions have some significant differences. After segmentation, image matching is performed according to the features of each region. The feature-based matching method is generally divided into four steps: feature detection, establishment of feature description, feature matching, and use of matched “feature pairs” to obtain image registration model parameters.
2. Oxygen detector
Oxygen detection alarm is a personal portable gas detection alarm. Its sensor adopts electrochemical sensor, which has a sensitive response and is suitable for continuously detecting the percentage concentration of oxygen in the ambient air of industrial and mining enterprises. Sound, light, and vibration alarms at the upper and lower limit, warn the on-site personnel to evacuate the dangerous area as soon as possible.
(1) Main features
1. Pocket type, compact and easy to use.
2. Powered by 9V laminated battery, easy to carry.
3. It is suitable for occasions of discontinuous monitoring. The performance is stable and the accuracy reaches 0.01%.
4. Cheap and practical.
・ Low power consumption and long standby time
・Built-in vibrator, suitable for very noisy environment when alarming
・ 6 super bright LED light-emitting tubes turn on and drive the buzzer to emit intermittent “di-di-” sound
・ Adopt LCD liquid crystal Display, full Chinese menu operation
・ High and low concentration alarms, and the full range of the alarm setting value can be adjusted.
・ Small size
・ Special shell material has good anti-slip effect
(3) Principle of oxygen detector
The air and the gas to be measured diffuse to the sensing electrode through the diffusion membrane. The control circuit maintains a voltage between the sensing electrode and the counter electrode sufficient to initiate an electrochemical reaction. The electrochemical reaction generated under the action of the gas to be measured creates an electric current between the two poles. The strength of this current is proportional to the concentration of the measured gas and is reversible.
The control circuit also develops a bias level between the sensing electrode and the reference electrode that does not create a current between the electrodes. The fast response of the sensor enables real-time, continuous detection of the surrounding air.