To create the perfect machine vision system, these factors cannot be ignored!

Visual inspection is therefore widely used in the production, assembly and packaging process, to detect defects to prevent defective products from entering the market and then affecting the corporate brand reputation has this immeasurable value.

The design of the machine vision system needs to consider many factors, in addition to selecting the equipment with the corresponding parameters according to the conventional selection parameters, it is also necessary to consider the stability of the light source, the distortion error of the camera, and the relative motion between the detected object and the camera and other factors brought to the detection system stability interference and measurement error. Only by considering these factors comprehensively to optimize the design of the vision system, can a stable and qualified machine vision inspection system be established.

1. Industrial cameras

The choice of industrial camera mainly considers its sensor type, resolution and frame rate, among which the sensor is divided into CCD and CMOS two kinds, CMOS image sensor integration degree is high, the distance between the components and circuits is very close, interference is relatively serious, imaging noise is high, CCD sensor camera relative to CMOS camera has high sensitivity, low noise and fast response characteristics.

If the enterprise does not have special needs, CCD sensor cameras are the first choice to ensure image quality and stability. In terms of stability, the impact and shock resistance of the CCD camera is also strong, in general, the CCD sensor camera is better than the CMOS camera in terms of imaging quality and stability.

In addition to the choice of camera type, the resolution and frame rate of the camera should be selected according to the required detection accuracy and detection speed in the specific purchase. Specifically, the appropriate resolution is determined by calculating the size of the field of view of the detected object and the distance between the camera and the measured object, and then the frame rate of the camera is selected considering the motion speed of the measured object and the detection accuracy requirements.

2. Industrial lenses

Another important factor affecting the picture quality of a camera is the lens of the camera.

In addition to selecting the right lens focal length, focal length, focal length and other basic parameters according to the actual working conditions, the important factor affecting the accuracy of network detection is that the error of the image geometry can not be eliminated, and only professional embedding can be carried out. Many industrial cameras use various methods to fill the errors caused by wide-angle lens changes, but in the high-precision detection industry, geometric graphics will affect the detection accuracy.

: Select the corresponding lens resolution according to the limit resolution of the camera, choose a camera that is greater than the limit resolution of the camera, but also need to calculate the focal length of the lens according to the working distance and field of view, and choose the appropriate depth of field according to the distance between the measured object and the camera. In addition to the correct selection of the above parameters, you can also choose the telecentric lens with small geometric distortion compared to the ordinary lens, the telecentric lens not only has small geometric distortion, but also can reduce the error caused by the change of object distance.

3. Light Source

The light source will increase the image features and defects, weaken the effect of interference and background image, and quickly affect the quality of the input information data.

Because there is no practical lighting equipment, light source design is a major problem that machine vision technology must solve, in general, not only for each special application to choose the type of light source, but also must be set according to the actual natural environment.

If there are no special requirements, the use of LED light sources should be given priority for visible light sources. In the uniformity of the light source that has a decisive impact on the quality of the acquired image, the LED light source is significantly better than other light sources such as halogen lamps and fluorescent lamps, and it also has the advantages of low power consumption, long service life and no pollution to the environment. In order to reduce the influence of external light on the stability of the visual system, external light sources can also be shielded by increasing the light source box.

4. Software testing

The stability of detection software is an important factor affecting the detection results of machine vision. The vision system will eventually use targeted algorithms on the computer to carry out a series of image processing such as image filtering, edge detection and edge extraction. Different image processing and analysis means as well as different detection methods and calculation formulas will bring different errors. The quality of the algorithm determines the measurement accuracy.

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5. External environment

The working environment factors of the vision system include ambient temperature, illumination, power supply voltage, dust, humidity and electromagnetic interference, etc. A good operating environment is the guarantee of the normal operation of the vision system.

External light will affect the illuminance of the object to be measured, increasing the noise of the image data output, and the change of the power supply voltage will also lead to the instability of the light source, resulting in noise that changes with time.

Temperature changes will also have an impact on the performance of the camera, the camera will mark the normal working temperature range when leaving the factory, electromagnetic interference is an inevitable interference factor in the industrial detection site, the impact on the industrial camera circuit, data signal transmission circuit and other weak circuits is particularly serious.

To minimize the interference of the external environment, in strict accordance with the use of machine vision inspection machine labeling guidelines, such as the camera will mark the normal working temperature range when leaving the factory, the factory should ensure that the machine works within the normal temperature.

The use of qualified visual products, qualified visual products will be subjected to strict anti-interference testing at the factory, greatly reducing the impact of external electromagnetic interference on the hardware circuit.