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1. What is a Camera?
A camera is an electronic device that captures images and converts them into digital or analog signals. It typically uses a semiconductor imaging sensor, such as a CCD or CMOS chip, which allows it to offer advantages like high sensitivity, reduced glare, minimal distortion, compact size, long lifespan, and resistance to vibration. These features make cameras suitable for a wide range of applications, from everyday use to specialized surveillance systems.
2. How a Camera Works
The process begins when light from the subject passes through the lens and is focused onto the image sensor. Each pixel on the sensor accumulates an electric charge proportional to the intensity of the light it receives. Under the control of timing signals, this charge is then transferred pixel by pixel. The signal is then processed, filtered, and amplified before being converted into a video output. This video signal can be sent to a monitor or television, allowing the user to view the same image captured by the camera.
3. Resolution Selection
Resolution is a key performance indicator for cameras, measured in line pairs per millimeter. Black and white cameras typically have resolutions between 380 and 600 lines, while color cameras usually range from 380 to 480 lines. Higher resolution means sharper and more detailed images. For standard surveillance purposes, a 400-line black and white camera is often sufficient. However, for critical applications like medical imaging or detailed analysis, a 600-line camera provides much clearer results.
4. Imaging Sensitivity
Sensitivity refers to how well a camera performs in low-light conditions. It's usually expressed in lux, indicating the minimum amount of light required for proper operation. A black and white camera generally requires between 0.02 and 0.5 lux, while a color camera needs more than 1 lux. Cameras with 0.1 lux sensitivity are suitable for general surveillance, while those with 0.02 lux are better for night-time or dimly lit environments. When using near-infrared lighting, low-light cameras are essential. Lens aperture also affects sensitivity—e.g., 0.97 lux at f/0.75 is equivalent to 2.5 lux at f/1.2.
5. Electronic Shutter
The electronic shutter controls the exposure time of the image sensor, ranging from 1/50 to 1/100,000 seconds. Most cameras use automatic shutter settings, adjusting the exposure based on ambient light levels to ensure clear images. Some models allow manual adjustment for specific applications, such as capturing fast-moving objects or reducing motion blur.
6. External Synchronization and Triggering
External synchronization ensures that multiple video devices operate in sync, using a common signal to align frame and line timing. This is useful in multi-camera setups. However, true external triggering, which allows capturing a precise frame at a given moment, requires special cameras designed for this function.
7. Spectral Response Characteristics
Most cameras use silicon-based sensors, which are sensitive to visible and near-infrared light. The peak sensitivity is around 550 nm (green), and the sensor can detect up to about 1 micrometer. They are not sensitive to ultraviolet light due to built-in UV filters. Color cameras use red, green, and blue filters, making them less responsive to infrared and ultraviolet wavelengths. This makes them ideal for covert nighttime surveillance when combined with infrared illumination.
8. Chip Size
The size of the image sensor, often referred to as the "chip size," affects both the field of view and the overall camera size. Common sizes include 1/2", 1/3", and 2/3". A larger chip offers a wider angle of view with the same lens, while smaller chips allow for more compact designs.
The camera system is typically installed on-site and includes the camera itself, a lens, a protective housing, a mount, and sometimes a pan-tilt unit. Its main purpose is to capture and convert visual information into electrical signals. Cameras come in two main types: color and black and white. Black and white cameras generally offer higher sensitivity, making them ideal for low-light environments. If the goal is to monitor movement or location, a black and white camera may be preferred. However, for identifying details such as clothing colors or environmental elements, a color camera is more appropriate.
Camera specifications are often categorized by sensor size, such as 1/3 inch, 1/2 inch, or 2/3 inch. Installation options include fixed mounts or pan-tilt units, offering flexibility depending on the application.
3. Waterproof, dustproof, pressure resistant and corrosion resistant