Smart LED light source driver for machine vision system

摘要

The unique properties of LEDs offer significant advantages in terms of lifetime, intensity and color control, response time and efficiency, all of which are very important for illumination in machine vision applications. However, there are some drawbacks of LEDs, such as the high thermal dependency and temporal degradation of the intensity and color. Dealing with these drawbacks requires complex LED drivers, which are able to compensate for the abovementioned changes in the intensity and color, thereby maintaining higher stability over a wide range of ambient temperature throughout the lifetime of a LED light source. Moreover, state-of-the-art machine vision systems usually consist of a large number of independent LED light sources that enable real-time switching between different illumination setups at frequencies of up to 100 kHz. In this paper, we discuss the concepts of smart LED drivers with the emphasis on the flexibility and applicability. All the most important characteristics are being considered and discussed in detail: the accurate generation of high frequency waveforms, the efficiency of the current driver, thermal and temporal stabilization of the LED intensity and color, communication with a camera and personal computer or embedded system, and practicalities of implementing a large number of independent drive channels. Finally, a practical solution addressing all of the abovementioned issues is proposed with the aim of providing a flexible and highly stable smart LED light source driver for state-of-the-art machine vision systems.