EMBEDDED TECHNOLOGY
TechNexion, an Inelco Hunter Partner, explains E
ver since the third industrial revolution, researchers have constantly come up with newer innovations to help automate complex processes. Tasks that were once done using mechanical systems moved to digital with the help of computers and digital electronics. This also led to the birth of digital cameras in the late 1960s with the invention of image sensors.
From there, there was no looking back. Imaging technologies have got better and better over the years. While image sensors grew in quality, other camera components also saw drastic improvements. Camera interfaces are one such key component of an imaging system that plays a key role in the performance of the vision system. But what exactly is a camera interface? What is its function in a camera? What are the different types?
What is a camera interface? A camera interface is a communication channel between a camera and the host system. Depending on the type of the vision system, the host can be an ordinary PC, an industrial PC or a processor like the NXP
i.MX8. It is the camera interface that is responsible for transferring the image data captured by the camera to the host for further processing.
The camera interface is a key component in an imaging system because it has a huge role in deciding the quality of the image data. In addition, the bandwidth of the interface determines how fast the data can be transferred from the camera to the host. This in turn limits the frame rate you can achieve with a camera at a given resolution. Latency is another critical parameter of a camera interface. Some of the modern embedded vision applications require the latency to be in the order of a few milliseconds since they need a close to real-time response.
An example of such an application is an autonomous delivery robot used for delivering food and packages. Here, the interface used should be capable of transferring data without much delay for
the robot to quickly detect obstacles and respond to its surroundings for autonomous navigation.
Different types of camera interfaces used in embedded vision
There are plenty of camera interfaces used in consumer, industrial and commercial applications. The most popular ones used in embedded vision include Ethernet, USB, MIPI, FPD-Link and GMSL.
Choosing the right camera interface for your embedded vision system
The following are the factors you need to consider while selecting the camera interface:
Bandwidth and speed of transfer: Since today’s embedded cameras are designed to capture high-quality images, the interface should also support
high-bandwidth transmission in most cases. USB, MIPI, FPD-Link or GMSL can be a great choice in such scenarios. Distance of transmission: For long-distance transmission (beyond 2 to 3 meters), consider using FPD-Link III, ethernet or GMSL.
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MIPI will only work in systems where the camera and the host are placed close to each other (within 50 cm). Cost: SerDes interfaces and connectors like FPD-Link and GMSL are more expensive compared to USB, MIPI and ethernet. Between USB3 and USB2, the latter tends to be cheaper. Latency: Latency becomes extremely critical, especially in long distance applications. Ethernet is not recommended for low latency requirements. Both FPD-Link and GMSL offer excellent performance when it comes to latency. Multi-camera support: While USB, MIPI and ethernet can support multiple cameras, they have limitations when it comes to the number of cameras and effective bandwidth. It is wiser to go with a SerDes interface like FPD-Link or GMSL if you have more than four cameras to connect to a single host. Host platform: This is one of the most important factors that determines the choice of camera interface. For x86-based hosts, USB is the go-to choice whereas for ARM-based processors MIPI is preferred.
What is a camera interface? and what is its relevance in embedded vision?
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