In the field of machine vision, the light source is a crucial element. It not only affects the quality and clarity of the image but also directly affects the performance and stability of the system. This article introduces the types of light sources commonly used in machine vision and their characteristics to help readers better comprehend and choose appropriate light sources.

      1. Direct lighting

      Direct lighting is the most commonly used light source. It directly illuminates the object to be measured using high-brightness guided or halogen lights. The advantages of this light source are direct light, high brightness, and

      Ability to provide sufficient light intensity to meet the requirements of most machine vision applications. However, direct lighting also has some disadvantages, such as shadows, reflections, and glare, which may affect image quality and system stability.

      2. Indirect lighting

Indirect lighting is a lighting method that reflects light from a light source onto an object to be measured through one or more reflectors. The advantage of this light source is that it can reduce problems such as shadows, reflections , and glare and improve image quality. In addition, indirect lighting can adjust the position and angle of the light source as required to adapt to different application scenarios. However, the disadvantage of indirect lighting is that additional reflectors are required, which can increase the complexity and cost of the system.

      3. Backlight source

      A backlight source means that light is emitted from the back of an object and is reflected by optical elements to form an image. The advantage of this light source is that it can improve the contrast and brightness of the image, making it suitable for scenes in which details need to be emphasized. However, the disadvantage is that it requires precise optical design and dimming technology; otherwise, problems such as reflection and light leakage may occur. Common backlight sources include CCD and CMOS cameras.

      4. Hemispheric light source

      A hemispheric light source means that the light is evenly distributed within a hemispheric surface, which is suitable for scenes that require a panoramic view. The advantage of this light source is that it can provide uniform light coverage and avoid the problem of local excessive strength or weakness. However, the disadvantage is that it is more expensive and requires precise optical design and adjustment technology. Common hemispheric light sources include laser hemispheric mirrors and xenon balloons.

      5. Natural light

      Natural light refers to the light that enters the room from windows, skylights or other open spaces. The advantages of this light source are that it requires no additional equipment, is low cost, and can provide continuously adjustable light intensity. However, natural light also has some shortcomings, such as strong directionality of light, unstable color temperature, etc. These problems may affect the quality of the image and the stability of the system. Therefore, when using natural light as a light source, it is usually necessary to use special filters or reflectors to improve light conditions.

      6. Artificial light

      Artificial light is a light source generated by special lighting equipment. Its advantage is that it can accurately control the color, intensity, direction and other parameters of the light.

      Artificial light generally includes the following types:

      Fluorescent Lighting: Fluorescent light sources have stable brightness and color temperature, making them ideal for applications that require precise lighting control. In addition, the spectral distribution of fluorescent light sources can be adjusted to meet specific visual needs by adding special filters or using different phosphors.

      LED light source: LED light source provides extremely high energy efficiency and flexibility. They provide consistent brightness over a wide color temperature range and can be programmed for precise switching times as needed. However, the spectral distribution of LED light sources may be affected by their materials and manufacturing processes, which may have implications for certain applications.

      Laser light source: Laser light source provides extremely pure, uniform light and can provide very high light intensity. Since the light from laser light sources contains almost no infrared component, they are generally more suitable than other light sources for high-precision measurement and inspection tasks. However, laser light sources are relatively expensive and require professional installation and maintenance.

      Summary: The types of light sources in machine vision include direct lighting, indirect lighting, natural light and artificial light, etc. Each light source has its own unique advantages and disadvantages, and the choice of which light source depends on specific application needs and scene conditions. In practical applications, it is usually necessary to comprehensively consider factors such as the brightness, color temperature, and directionality of the light source to obtain the best image quality and system performance.