The "Signal Code" of Line Scan Cameras: In - Depth Analysis of Single - Ended and Differential Signals

In the field of machine vision, line scan cameras act like "clairvoyant eyes", shouldering the important task of high - precision detection and identification of various objects. Inside the camera, the triggering connection methods of the encoder, especially single - ended signals and differential signals, play a crucial role in the camera's performance. So, what exactly are single - ended signals and differential signals? What are the differences, advantages, and disadvantages between them?

As a traditional and basic signal transmission method, the principle of single - ended signals is easy to understand. It uses a combination of one signal line and one ground line to complete the signal transmission. In this mode, the signal line is responsible for carrying the signal to be transmitted, while the ground line serves as a reference potential, providing a benchmark for the signal. This method has a simple structure and was widely used in early electronic devices. Due to its high integration level and relatively low power consumption, most low - level signals on the market are transmitted using single - ended signals. However, the very feature that brings its advantages also causes its disadvantages. The simple structure leads to obvious drawbacks. Single - ended signals have poor anti - interference ability. In complex electromagnetic environments, the signals are easily interfered with, resulting in signal distortion and affecting the normal operation of the device.

Different from single - ended signals, differential transmission adopts a more ingenious design concept. In differential transmission, two signal lines are used to transmit signals simultaneously. The signals on these two lines have equal amplitudes but opposite phases. This unique transmission method endows differential signals with many remarkable advantages. Firstly, it has extremely strong anti - interference ability. When external interference occurs, the interference noise is added to the two signal lines in an equal - value and simultaneous manner. Since the original signals on the two signal lines have opposite phases, the interference signals cancel each other out, so that the signal obtained at the receiving end is not affected by interference. Secondly, differential signals can effectively suppress electromagnetic interference. Because the two signal lines are very close to each other, the signal amplitudes are equal, the amplitudes of the coupled electromagnetic fields between them and the ground line are also the same, and the signal polarities are opposite, so the electromagnetic fields cancel each other out, greatly reducing the electromagnetic interference to the outside. Thirdly, differential signals are less affected by the ratio of the threshold voltage to the signal amplitude voltage, which makes them perform better in the transmission of low - amplitude signals. They can achieve continuous and accurate positioning, showing obvious advantages in the application of line scan cameras with extremely high precision requirements.

However, differential signals are not perfect. In the case of extremely tight circuit board space, they have certain limitations. Since differential signals require the two lines to be of equal length, equal width, closely spaced, and on the same layer, when the pin pitch of the chip is extremely small and only one wire can pass through, differential signals cannot be used normally. On the other hand, single - ended signals, with their simple structure, are more flexible in space utilization.

In practical applications, considering the high requirements of line scan cameras for signal stability and accuracy, most line scan cameras currently choose to use differential signal connection methods. But single - ended signals have not been completely phased out. In some scenarios where the requirements for signal accuracy are not high and the electromagnetic environment is relatively stable, they can still give full play to their advantages of low cost and simple design. Understanding the characteristics and differences between single - ended and differential signals is of great significance for deeply understanding the working principle of line scan cameras and rationally selecting signal transmission methods in different application scenarios. With the continuous development of technology, more advanced signal transmission methods may emerge in the future. But at present, single - ended and differential signals still play important roles in their respective fields.