What are the factors that affect the visual inspection effect?

Machine vision inspection equipment can effectively improve inspection efficiency, save labor, reduce production costs, and thus enhance economic benefits. However, many factories and enterprises now buy their testing equipment back because the operators lack experience, which often affects the testing effectiveness of the equipment due to some minor issues during the production process.

Environmental impact: The impact of the environment on machine vision hardware is not only destructive to the hardware itself, but also affects the measurement results. For example, in environments with temperature changes, most industrial cameras can operate between -5 degrees and 65 degrees. In practical environments, excessively high temperatures often cause noise in camera imaging. However, this can be improved by improving the lighting method to enhance the signal-to-noise ratio.

Hardware selection: Stable image feature extraction is a prerequisite for image analysis and recognition, ensuring a stable imaging transmission to the image processing center is necessary to ensure the accuracy of software image processing. Many factors can affect the stability of imaging, such as the surrounding environment, changes in objects, and the impact of visual hardware. The selection of hardware for visual inspection is a challenging task that requires engineers to be very familiar with both the hardware itself and the hardware supplier, and to have sufficient selection experience. The environment faced by machine vision systems running in laboratories and systems running in actual work scenarios is vastly different.

Visual inspection includes important components such as light sources, lenses, cameras, image acquisition cards, data transmission, image processing, and measurement software. As the performance of various components improves, the capabilities of machine vision systems also grow exponentially. The complexity of the system depends on specific application requirements. Choosing the best components not only depends on whether the performance of the components can meet the requirements (such as resolution, frame rate, measurement algorithm, etc.), but also on the environmental conditions in which the system is ultimately located. For example, in the industrial field, these environmental conditions include component changes, loading, positioning, processing interfaces, vibration, ambient light, temperature, dust, oil pollution, water, electromagnetic radiation, etc. Under extremely harsh conditions, it is sometimes necessary to add protective measures to machine vision components. A typical example is that some cameras need to be used in relatively clean environments. However, in general, industrial environments can meet the direct use of industrial cameras. Even a stable visual system often produces unsatisfactory results due to external influences, such as vibration causing image blur and distortion, variable parts resulting in different images, and prolonged exposure time causing image sharpness distortion of moving objects.

Temperature can affect the performance of LED light sources. As the temperature of the LED increases, its brightness decreases. This can be compensated for by a light source controller for brightness output. The heat generated by LED itself can also accelerate aging and even lead to direct scrapping, so good thermal design is needed.

Other components also have corresponding temperature limits, such as industrial controllers/embedded PCs that can generally be used in industrial environments, but without fans, the PC is likely to be scrapped. In order to ensure the stability of visual imaging, in addition to selecting good hardware, we also need to consider the sensitivity of the measured object itself to temperature. For example, metal objects have thermal expansion and contraction to temperature, so when measuring such objects, their length and volume will change.

Vibration: Most industrial cameras have undergone anti vibration treatment, and robots and track cables can effectively prevent the camera from being affected by vibration during movement. A locked connector can prevent the camera from being subjected to vibrations. Durable PCs and embedded computers have excellent stability protection mechanisms. The fixed focus lens uses a metal interface locking screw to ensure that it is not affected by vibration. The filter to some extent protects the lens.

Environmental light: Daily filters can to some extent avoid the influence of environmental light, as they can change the information of light entering the sensor. By using high brightness modulated light sources, reducing sensor exposure time and aperture, the impact of ambient light can be minimized. Using infrared and other wavelength cameras for measurement can reduce the impact of visible light.

Dust, dirt, and water: Many cameras can achieve an IP65/67 protection level, ensuring dust and water resistance. Dust, dirt, liquids, and vapors often adhere to the surface of LEDs or lenses, affecting imaging. Adjustments can be made by increasing the camera gain, software image processing, and adjusting the LED output. Various environmental factors can have an impact on imaging, and these impacts can be fatal because images are important reference points for measurement.