What are the differences among co - axial light sources, bar light sources and ring light sources?

Coaxial light source, bar light source, and ring light source are three commonly used light sources in machine vision systems. Below, the editor will mainly introduce their main differences from the following aspects.

Structure and Light Emitting Principle

· Coaxial light source: It is composed of a light source, a collimating lens, a reflector, or a polarizer, etc. The light emitted by the light source is transformed into parallel light through the collimating lens, and then through components such as the reflector or polarizer, the light propagates along the optical axis direction and finally illuminates the surface of the object. Its characteristic is that the light emitting direction coincides with the optical axis of the camera lens, which can reduce shadows and reflected glare, and is suitable for the detection of objects with high requirements for surface flatness.

· Bar light source: It is usually composed of multiple light-emitting diodes (LEDs) arranged in a straight line and packaged with a circuit board and a housing. Its light emitting principle is to use the fact that LEDs emit visible light after being powered on. By controlling the number, spacing, and luminous intensity of the LEDs, a bar-shaped illumination area is formed. It is often used for the edge detection of objects, contour measurement, and the detection of elongated objects.

· Ring light source: Multiple LEDs are evenly distributed on a ring-shaped circuit board to form a ring-shaped light-emitting area. Its light emitting principle is also based on the light emitting characteristics of LEDs. Through a reasonable design of the ring structure and the layout of the LEDs, the light can be evenly illuminated on the surface of the object. It is suitable for occasions that require uniform illumination, especially for the detection of circular or arc-shaped objects.

Illumination Effect

· Coaxial light source: It can provide a high-contrast, shadowless illumination effect, especially suitable for detecting objects with specular reflection or highly polished surfaces, such as metal parts, glass products, etc. It can highlight the tiny defects and textures on the object surface, making the detection results more accurate.

· Bar light source: It can generate high-intensity linear illumination, forming a bright light band on the object surface, which has a very good enhancement effect on the edges and contours of the object. It can clearly outline the shape of the object, making it convenient for tasks such as edge detection and dimension measurement.

· Ring light source: It provides uniform ring-shaped illumination, which can eliminate the shadows and reflections on the object surface, making the overall illumination of the object uniform. For circular objects or scenes that require all-round uniform illumination, such as bottle cap detection, wafer detection, etc., the ring light source is an ideal choice.

Application Scenarios

· Coaxial light source: It is often used in chip detection in the electronics manufacturing industry, PCB board detection, as well as lens detection and prism detection in the manufacturing of optical components. In these applications, it is necessary to clearly observe the microscopic structure and defects on the object surface, and the coaxial light source can provide high-quality illumination conditions.

· Bar light source: It is widely used in barcode recognition in the logistics industry, part dimension measurement in mechanical manufacturing, and print quality inspection in the printing industry. Its linear illumination characteristics can highlight the edge information of the object, helping to improve the accuracy and efficiency of detection.

· Ring light source: It is widely used in bottle body detection in the food and beverage industry, medicine bottle detection in the pharmaceutical industry, wheel hub detection in the automotive manufacturing industry, etc. It can evenly illuminate the surface of the object, making it convenient to detect problems such as the appearance defects and dimensional deviations of the object.

Installation and Use

             · Coaxial light source: During installation, it is necessary to ensure that the light source is strictly aligned with the optical axis of the camera to ensure that                the light can accurately illuminate the surface of the object and be reflected back to the camera. Special installation brackets and adjustment mechanisms                  are  usually required to achieve precise installation and debugging.

· Bar light source: The installation is relatively flexible, and it can be installed at different positions such as above, on the side, or below the object according to the detection requirements. When in use, it is necessary to adjust the length, width, and luminous intensity of the bar light source according to the size of the object and the detection requirements to obtain the best illumination effect.

· Ring light source: It is generally installed around the camera, maintaining a certain distance and angle from the camera. During the installation process, attention should be paid to the concentricity and perpendicularity of the light source to ensure that the light is evenly illuminated on the surface of the object. In actual use, the inner diameter, outer diameter, and light-emitting angle of the ring light source can be adjusted to adapt to the detection of objects of different sizes and shapes.