Learn about the applications and precautions for the use of machine vision backlights

Machine vision backlights can be divided into two categories: side backlights and bottom backlights. As the name suggests, the side backlight is surrounded by light-emitting strips around the light guide plate, and the light is diffused downward through the action of the light guide plate. The bottom backlight is a compact array of LEDs on the panel, which are evenly dispersed through the diffuser panel.

Applications of machine vision backlights

It is mainly used for contour detection of the measured object, stain defect detection of transparent body, liquid crystal text inspection, size and shape inspection of small electronic components, bearing appearance and size inspection, semiconductor lead frame appearance and size inspection, etc.

Features of machine vision backlight:

1. It has better uniformity

2. The light is soft and natural, and the brightness is high

3. Multi-color backlight can be customized, suitable for special occasions

4. High-density LEDs are distributed at the bottom of the light source

Precautions for the use of machine vision light sources

The use of LEDs in high-temperature environments shortens their lifespan

*Red LEDs, in particular, will lose 1% for every 1 degree increase in temperature.

*Prolonged use at high temperatures will gradually deteriorate and reduce brightness.

How to use the light source correctly to prevent aging and brightness degradation caused by its own heating

■Use the light source with the lowest possible brightness level

At the right brightness, the light source is lowered to reduce the amount of current, so less heat is emitted and brightness loss is avoided. If the brightness decreases due to long-term use, the brightness level can be gradually increased.

■A fan can be installed or air flow can be provided to dissipate heat, and the temperature can be lowered to slow down the decay of brightness.

Install a fan ------ provide airflow ----- install a heat-dissipating bracket.

■The light source can be turned on only during imaging or the strobe controller can be used.

Switching on and off the LED light source several times in a row has little effect on its service life. When the LED is turned on as a strobe source or only according to external signal requirements, the brightness of the light source is stable and the LED lifetime is significantly extended.

Precautions for selecting machine vision light sources

1. Understand the system structure and operation requirements, and determine the spatial structure relationship between the camera, the light source and the measured object. The parameters to be determined are: Field of View (FOV) and Working Distance (WD).

2. The spatial structure includes: direct radiation, side irradiation, and back irradiation.

The light source of the direct structure is a part of the ring light source, the coaxial light source, and the garden top light source.

The light source of the side-emitting structure is a part of the ring light source, the bar light source, the line light source, and the point light source.

The back illuminates a square backlight, a strip backlight, a paper backlight.

3. For the observation and analysis of the measured items, the dome light source should be used for curved surface detection, the coaxial light source should be used for smooth planes, the brightfield light source should be used for rough planes, and the infrared light source should be used for objects with good light transmittance. Distinguish what color the back (we don't need to detect) and what color the foreground (what we want to detect).

4. A good light source can improve the contrast of the image - the background and foreground are very clear, and the color of the foreground is varied, and it is advisable to use a color light source or a white light source.