概述

Traditionally, one IP camera has only one lens and one sensor. Its field of view covers a certain part of the surroundings. When the width of the view is not sufficient, then sometimes multiple cameras are installed next to each other, facing different directions. Nowadays, such situations can be resolved using multi-imager cameras - it has two or more lenses inside a single device.

Panoramic View Solutions
Some of the multi-imager cameras are designed so that the lenses cover the view so that there are no blind spots between them. The cameras are called panoramic multi-imager cameras as they form a seamless panoramic view. Depending on the number of lenses, the panoramic view can cover 180 degrees or even 360 degrees, without any blind spots.

Some of the panoramic multi-imager cameras deliver the video streams to the VMS as individual channels. NVR records them separately, however, when placed next to each other in the NVR live view or playback layout, then they form a nice panoramic view.

There are also panoramic multi-imager cameras that are able to stitch the aligned video streams into one single video stream. NVR receives only one stream from that camera, which has a very wide display ratio. The benefit of the stitched video stream is the simplicity on the VMS side - you do not have to care about aligning the views together using VMS layout features.

The panoramic multi-imager cameras can be adjusted during the installation by moving either the bracket of the camera or the gimbal of the lens. Regardless, all the lenses move up-down or left-right together as one rigid structure, thereby maintaining the proper alignment at all times.

From the application perspective, the panoramic multi-imager cameras produce very similar view compare to the fisheye lens cameras, but the difference is in the video quality - multi-imager cameras can have much more pixels per foot in any direction. While the fisheye lens cameras have lower cost and are used mostly for the overview purposes, the multi-imager cameras produce clear details that can be used for the face recognition, ALPR and other applications that require detailed images.

Multi-Directional View Solutions There are also multi-imager cameras that allow adjusting each of their lenses independently. They do not necessarily need to be aligned to form a panoramic view. It is up to the user to decide how the lenses are adjusted in terms of pan, tilt and rotation.

These independently adjustable multi-imager cameras are also called Multi-Directional cameras. The purpose of the multi-directional camera is to have one device replacing multiple conventional cameras. This makes the installation really convenient - only one PoE cable is needed for that camera, and multiple independently adjustable video feeds can be produced.

Multi-directional cameras may have fixed, vari-focal or even zoom lenses that can be individually adjusted. In case of zoom lenses, it is possible to use VMS interface to zoom in or out if necessary. These zoom lenses also have auto focus. Each sensor of the multi-directional camera produces independent video stream.

The simplest multi-directional cameras are dual domes - these are small devices with two dome bubbles, covering one fixed lens each. The dual domes can be adjusted to cover the opposite directions of the same corridor, or have them at the corridors intersection, facing both directions.

More advanced multi-directional cameras have 4 or more lenses with zoom and auto focus capabilities.

应用

Multi-imager cameras are used for producing high resolution panoramic images, or to have one camera replacing multiple conventional cameras.

Perimeter surveillance, parking lot monitoring, traffic monitoring, city surveillance - all these applications benefit greatly from the multi-imager solutions.

解决方案

The multi-imager cameras can be connected to the VMS, such as ACTi's NVR 3 or CMS 2. Depending on the type of the multi-imager cameras, the number of the video channel licenses may vary - in case of stitched images, only one VMS channel license is being occupied. In case of non-stitched solutions, each of the independent streams would occupy its own channel.

When streaming a stitched video to the VMS, the display ratio is usually very wide, perhaps 2:1 or even 3:1. To preserve this aspect ratio in the live view or playback page, ACTi's VMS has been designed to have an adaptive view grid management - it is possible to merge the grid cells so that the super wide image will displayed with the perfect aspect ratio.