Visual light sources, in conjunction with a vision system, can achieve three main functions: First, positioning, automatically determining the location of sensed objects and products, and displaying the product's surface features, outline, color, numerical values, and number of objects under a CCD; second, measurement, which uses forward-facing and backlighting methods to automatically measure the product's shape, diameter, height, area, and distance between two materials; and third, appearance inspection, widely used in the vision industry for appearance inspection, using various types of light sources to display the surface, interior, and all relevant features of materials. Examples include: in the 3C industry, the mobile phone frame, screen appearance, and camera appearance; and in the printing industry, checking the correctness of box packaging, printing errors, scratches, damage, and oil stains.
Shenzhen TSD Technology Co., Ltd. (hereinafter referred to as TSD), established in 2012, is a professional manufacturer specializing in the R&D, design, production, and high-quality products and technical services of machine vision light sources. It also specializes in the sales and distribution of machine vision-related products, and can provide complete hardware and vision solutions and services. TSD produces ring lights, shadowless lights, AOI light sources, spherical integrating lights, bar lights, bar combined lights, coaxial lights, side lights, free surface lights, surface lights, backlights, point lights, prisms, linear light sources, analog controllers, digital controllers, point light source controllers, linear light controllers, and other products. Customized light sources are also available upon request.
The following are two case studies on visual inspection using ultraviolet and infrared light sources for imaging.
What is ultraviolet light?
Ultraviolet (UV) light has a higher frequency than visible light but a lower frequency than X-rays. In the electromagnetic spectrum, UV light ranges from 400 to 10 nm in wavelength. This range begins at the high-frequency limit of visible light and overlaps with the low-frequency range of X-rays. UV light is divided into three types: UVA, UVB, and UVC (UVA, UVB, and UVC, respectively), with wavelength ranges of 400–315 nm, 315–280 nm, and 280–190 nm. Industrially used UV light sources typically have wavelengths around 340 nm to 400 nm.
Project Requirements: Inspect the adhesive in the center of the diaphragm coil in the 3C industry.
Client requirements: The outline of the center glue should be clear and the contrast should be obvious; the field of view should be of moderate size.
Using a color camera
Material Analysis: The material surface is smooth and highly reflective. Testing with W/B/R colors reveals insufficient contrast between the adhesive and the material, hindering algorithm detection. However, using a UV light source significantly excites the adhesive on the material surface, brightening it and providing high contrast, thus facilitating algorithm detection.
Material diagram
Imaging effect of ultraviolet light source 1
Image 2 of ultraviolet light source imaging effect
The image produced by the ultraviolet light source clearly shows the outline of the adhesive, forming a significant contrast with the material surface, which is beneficial for software algorithm detection. Commonly used ultraviolet light sources include coaxial ultraviolet light sources, strip ultraviolet light sources, ring ultraviolet light sources, dome ultraviolet light sources, point ultraviolet light sources, and contour ultraviolet light sources.
Application examples: 3C industry, adhesive plastic shell spraying (mobile phone cases), magnesium alloy spraying (laptop cases), various PVC (such as IC cards), plastic sheets, UV oil printing, inline varnishing of offset printing machines; special printing of paper products, water drying and curing of computer keyboard printing, PCB graphic transfer; fluorescent banknote detection, ITO glass.
Imaging environment:
What is an infrared light source?
Infrared (IR) radiation is electromagnetic radiation with frequencies between microwaves and visible light. Infrared radiation can be divided into three parts: near-infrared (high-frequency infrared radiation, higher energy), with wavelengths between (3~2.5) μm and (1~0.75) μm; mid-infrared (medium-frequency infrared radiation, moderate energy), with wavelengths between (40~25) μm and (3~2.5) μm; and far-infrared (low-frequency infrared radiation, lower energy), with wavelengths between 1500 μm and (40~25) μm.
Infrared (IR) wavelengths, typically between 700µm and 1350µm, are commonly used in visual light sources. They are frequently used for detecting the internal dimensions of screens and for eliminating surface interference in the packaging industry.
Project requirement: To measure the inner screen size of an LED screen.
Client requirements: clear edge contrast; moderate field of view.
Material Analysis: The sample surface is smooth and exhibits specular reflection. Using a high-angle visible light source for detection results in significant surface reflection. While a low-angle visible light source can eliminate reflection, it cannot penetrate the surface to detect the inner screen. Therefore, an invisible infrared (IR) light source is used to penetrate the material surface and detect the edge of the inner screen, as shown in the diagram below:
Material diagram
Infrared light source effect diagram
Ordinary light source effect diagram
Application examples: Due to its strong penetrating power, infrared light is often used for products that require surface inspection to detect internal LED screens, as well as materials such as films and packaging bags.
To facilitate customer testing and product selection, Topvision provides free test samples and vision solutions, aiming to deliver results exceeding customer expectations. Since its inception, Topvision has adhered to a spirit of hard work and innovation, upholding the values of integrity and gratitude. In its development, it has continuously attracted top talent in electronics, mechanics, and image processing, working together to innovate in the field of machine vision and contribute to the advancement of industrial automation.
