**I. Overview**
In the field of television monitoring systems, infrared technology has been widely used in the past. However, as crime rates have increased in modern society, the role of infrared night vision surveillance has become even more critical. It is now not only adopted by high-security locations such as banks, oil depots, armories, libraries, and prisons, but also commonly used in general surveillance systems and even residential areas. This trend highlights the growing demand for standardized and reliable monitoring solutions, with more and more important sites requiring 24/7 continuous surveillance.
To achieve night vision, traditional visible light illumination can be used, but this method lacks concealment and may even expose the target. Covert night vision is now primarily achieved through infrared camera technology. There are two main types: passive and active infrared cameras. Passive infrared (PIR) technology detects heat emitted by objects above absolute zero, such as humans or warm objects, which emit strong infrared radiation. However, PIR systems are rarely used in night vision due to high costs and their inability to capture environmental details. Active infrared technology, on the other hand, uses specially designed "infrared lamps" to emit invisible infrared light that can be captured by standard cameras. This allows black-and-white CCD cameras or color cameras that switch to black and white at night to effectively capture images in low-light conditions.
**II. Principles and Characteristics of Infrared Cameras**
Light is an electromagnetic wave that spans a wide range of wavelengths, from a few nanometers to about one millimeter. Human eyes can only perceive a small portion of this spectrum, known as visible light, which ranges from 380 nm to 780 nm. Beyond this range lie ultraviolet and infrared light. Infrared light has longer wavelengths than visible light and is typically divided into two categories: semiconductor-based infrared emission (such as infrared LEDs) and heat radiation-based infrared.
Infrared LEDs are widely used in consumer applications. They consist of a matrix of infrared-emitting diodes made from materials like gallium arsenide (GaAs). When a forward bias is applied, the PN junction emits infrared light, typically centered around 830–950 nm with a half-peak bandwidth of about 40 nm. These wavelengths are within the sensitivity range of most black-and-white CCD sensors. One major advantage of using infrared LEDs is that they can avoid red glare when operating at 940–950 nm, or produce only a weak red glow otherwise. Additionally, they offer long lifespans. The irradiance of these LEDs is measured in microwatts per square meter, and their output power is proportional to the forward current. However, excessive current can cause overheating, reducing performance and lifespan. To address this, some advanced models, such as Fujifilm's FI-930C and FI-970C, incorporate efficient LED designs and built-in cooling systems, ensuring stable operation for up to 25,000 hours.
**III. Selection and Use of Infrared Lamps**
When selecting an infrared camera system, it is essential to consider the complete setup, including the infrared lamp, camera, lens, protective housing, and power supply. Most cameras on the market come separately from infrared projectors, so careful planning is required during system design. Key considerations include whether to use a black-and-white camera with an infrared lamp or a color camera, as well as installation and waterproofing requirements.
Black-and-white cameras generally have a broader light-sensing range, extending into the infrared spectrum, making them suitable for use with infrared illumination. Color cameras, however, are limited to visible light and cannot effectively utilize infrared lamps. Some day-and-night cameras use dual CCDs or digital switching to adapt to different lighting conditions, but this may result in lower brightness or color distortion. Integrated infrared cameras, such as the FI-930C and FI-970C from Fu-Kang, combine the camera, lens, protective cover, and infrared light source into a single unit. These models feature high-quality aluminum casings, IP55 waterproof ratings, and an integrated design that simplifies installation and maintenance.
With the rapid growth of infrared night vision systems, more manufacturers are entering the market. However, not all products are of equal quality, and differences in technology, detection capabilities, and performance should be carefully evaluated. Users are advised to compare options thoroughly before making a purchase.
When using infrared equipment, users should always read the manual carefully, especially the safety instructions. They should verify that all supporting components meet the necessary requirements and consider any influencing factors. If any component does not meet specifications, adjustments should be made promptly to ensure optimal performance.
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