Security Camera

Security camera is an electro-optical device designed to monitor a specific area, record images, or transmit them to a remote location. In literature, it is commonly defined as the primary component of CCTV (Closed-Circuit Television) systems. Unlike television broadcasting, these systems transmit images not to the public but exclusively to authorized monitoring points.

Basic Working Principle

The fundamental function of a security camera is to convert light entering through the lens into electrical signals. The process consists of the following stages:

1. Light Collection: The lens gathers light from the subject and focuses it onto the image sensor.
2. Conversion: The image sensor (CCD or CMOS) converts light photons into electrical charges.
3. Processing: The signal processor (DSP) transforms this data into a digital image, adjusting color, contrast, and sharpness.
4. Transmission: The image is sent to a recording device (DVR/NVR) or display via wired (coaxial/Ethernet) or wireless methods.

Image Sensor Technologies

Two main types of sensors are used in security cameras:

• CCD (Charge-Coupled Device): Offers high sensitivity to light and produces less noise in low-light conditions. However, manufacturing costs are higher.
• CMOS (Complementary Metal-Oxide-Semiconductor): Consumes less power and processes image data more quickly. CMOS sensors are now preferred in most high-resolution (4K and above) IP cameras.

Camera Types and Classification

Security cameras are categorized based on their intended use and physical design:

A. By Signal Transmission Method

• Analog Cameras: Transmit images as analog signals via coaxial cables. They require a DVR (Digital Video Recorder) to record the footage.
• IP (Internet Protocol) Cameras: Convert images into digital data and transmit them over a local area network (LAN) or the internet. They have built-in processors and IP addresses.

B. By Physical Design

• Dome Cameras: Have a semi-spherical shape. Typically mounted on ceilings for indoor use; vandal-resistant models are available.
• Bullet Cameras: Feature a cylindrical design. Commonly used outdoors or for monitoring specific directions due to their long-range viewing capability.
• PTZ (Pan-Tilt-Zoom) Cameras: Can be controlled remotely. They can rotate horizontally, tilt vertically, and perform optical zoom.

Technical Components and Features

• Resolution: Determines the amount of detail in the image. Measured in pixels (e.g., 1920x1080 – Full HD).
• Infrared (IR) Illumination: Uses IR LEDs around the camera to capture images in complete darkness. This invisible light is detected by the sensor to produce black-and-white night vision.
• WDR (Wide Dynamic Range): A technology that balances light levels between very bright and very dark areas in a scene to prevent loss of detail.
• Focal Length: Expressed in millimeters (mm). Lower values (e.g., 2.8mm) provide wide-angle views, while higher values (e.g., 12mm) offer narrow-angle views with greater distance coverage.

Storage and Data Management

The following methods are used for storing video footage:

• DVR (Digital Video Recorder): Converts analog signals into digital format and records them onto a hard drive.
• NVR (Network Video Recorder): Receives and stores digital data directly from IP cameras over a network.
• Cloud Storage: Stores data on remote servers via the internet.