Flexible’ Machine Vision: Sensors, Lenses, and Software
- Saturday, 01 June 2013
Machine vision has become indispensable in today’s highly automated manufacturing environments, which rely on accurate in spec tion to ensure high product quality and high process efficiency. Applications for the technology span industry, and include everything from validation of printed barcodes and text on consumer product labeling, to assembly verification of printed circuit boards, to dimensional measurement of automotive parts. The demand for vision inspection only continues to grow with increasing throughput requirements and stringent quality standards that necessitate full inspection and render manual product inspection unfeasible.
The prevalence of machine vision inspection and identification in manufacturing operations has also grown the user base of the technology. What was once exclusively the realm of experienced vision specialists is now being done by users ranging from factory-floor operators and manufacturing engineers to system integrators and OEMs. With application requirements and a broad range of skill levels to accommodate, vision system manufacturers have sought to develop technologies that are both easy to use and implement, yet maintain the flexibility to address expanding requirements. New hardware and software products provide the ability to adapt to changing application demands, enabling easy system modification while at the same time protecting the users’ time and investment.
Cameras have become more modular as new smart cameras pack complete vision systems into miniaturized form factors, with lens and lighting options to address a multitude of system con figura - tions and allow for modification. Recent advances in CMOS sensor technology enable high-resolution, high-speed models that are both cost-effective and easy to use. New software developments, similarly, are scalable to accommodate applications that expand beyond their original scope; users are no longer locked into a single hardware/software technology. The software features portability from one device to another, and its current graphical subsystems produce intuitive user interfaces. In this article, we’ll explore these three technologies — sensors, lenses, and software — providing machine vision tools with a greater flexibility.
Advances in CMOS Sensor Technology
Current CMOS sensor technology has made smart camera systems a viable option for more users than ever. Traditionally more expensive, more complex, and physically larger than CMOS technology, CCD sensors were, until recent years, required to address applications requirements for motion, high resolution, and image quality. Advancements in CMOS sensors have bridged the gap in image quality. Now available in both high resolution and with a global shutter, CMOS technology enables smart cameras with freeze motion performance at resolutions of 1MB+. While CCD sensors still hold a place in certain applications, such as precision measurement where image quality is critical and very high resolution is required, the benefits of CMOS technology have made it an attractive replacement to CCD devices in many applications.
CMOS sensors feature a simple design and high-speed data transfer, thanks to their ability to quickly get rid of pixels. CCD technology is physically limited on how fast the images can exit the sensor. CMOS is very low powered and therefore builds up less heat; smaller designs are possible because the boards are less complex and require fewer components (see Figure 1). In addition, CMOS technology has the ability to take sections or windows of an image in order to further increase frame rates. Microscan’s 2MP Vision HAWK smart camera, for example, incorporates a high-resolution CMOS sensor to achieve frame rates of up to 300 frames/sec (see Figure 2).
Configurable Lens and Lighting Options
A variety of lens and lighting options are available for use with today’s modular smart cameras. Microscan’s Vision HAWK model uses interchangeable Cmount lenses and external lighting. Other new smart camera designs feature a fully integrated lens and lighting for equipment integration. Some offer the ability to “mix and match” accessory options, allowing system designs tailored to specific application needs.
Fully integrated liquid lens technology is valuable for production lines where the camera is out of reach, or other cases where manual adjustments to the lens are impractical or undesirable. A liquid lens is made of two liquids. A supplied voltage alters the curvature of the liquid, resulting in a lens with a focus position that can be controlled without moving parts. Different field angle options with liquid lens configurations offer multiple field-of-view options (see Figure 3).