Machine vision systems primarily use three types of light sources: high-frequency fluorescent lamps, fiber optic halogen lamps, and LED lighting. The choice of light source aims to clearly distinguish the object being measured from the background, obtaining high-quality, high-contrast images. The correct selection of the light source directly affects the success or failure of the system, as well as its processing accuracy and speed. Today, we will introduce the performance advantages of LED light sources and how to choose them.
The selection of LED light sources involves three main steps:
I. Product Information to be Tested
Examples of applications include: visual inspection, OCR, dimensional measurement, and positioning; what do you want to detect? Such as foreign objects, scratches, etc.; surface condition, such as mirror finish, rough finish, etc.; material, surface color; field of view; dynamic or static; distance from the bottom of the lens to the surface of the object being measured; settings: illumination level, distance from the bottom of the illumination to the surface of the object being measured, etc.; surrounding environment; camera type, etc.
II. Basic Preliminary Knowledge:
1. Due to differences in material and thickness, their light transmission characteristics vary.
2. They vary in their ability to penetrate matter based on their wavelength.
3. The longer the wavelength of light, the stronger its penetrating power through matter; the shorter the wavelength of light, the greater its scattering rate on the surface of matter.
4. Transmitted illumination is a lighting technique that allows light to pass through an object and observes the transmitted light.
III. Selecting a light source:
1. Requirements: Stable and uniform;
2. Purpose: To distinguish the object being measured from the background as clearly as possible;
3. How to clearly obtain the density difference between the measured object and the background;
4. Binarization processing: In order to highlight feature points and make the feature image stand out, common lighting techniques include bright field of view and dark field of view.
In fact, the specific method for selecting a light source depends on practical experience in experimentation.
Performance advantages of LED light sources for machine vision
Low operating cost and long service life; can be made in various colors as needed, and brightness can be adjusted at any time; better heat dissipation and more stable light brightness; can be made in various shapes, sizes and various illumination angles; fast response, can reach maximum brightness in 10 microseconds or less; the power supply has an external trigger, can be controlled by a computer, has a fast start-up speed, and can be used as a strobe light; can be specially designed according to customer needs.
