An array camera is an optoelectronic device capable of producing a two-dimensional image of the scene being framed; the models used today in industrial environments consist of a solid-state sensor, i.e., a silicon chip.

Specialvideo integrates the best brands of industrial cameras for every machine vision application.
For each project, we select the model best suited to the customer’s expected results, optimising the cost/benefit ratio.

The most widespread technologies are those of CCD (Charge-Couple Devices) and CMOS (Complementary metal– oxide – semiconductor) sensors:

The two technologies remain complementary, however, and the choice of one or the other depends on the application and the availability of components on the market: there are cameras with high-performance CMOS sensors and higher costs than CCD cameras with mediocre performance.

The sensor consists of a set of photosensitive elements (called pixels), capable of transforming incident light into an electrical signal. In the most common configuration, the pixels are arranged in a rectangular matrix, whose dimensions can vary from a few millimeters to over 35 mm diagonally.

The CMOS technology can offer very high-speed performance, capable of hundreds or thousands of images per second.

The main drawbacks of these sensors are fixed pattern noise and reduced sensitivity, as the pixel is partially occupied by the conversion electronics. Over time, these drawbacks have largely diminished thanks to technological developments.

The image acquisition can be done in two ways: global shutter or rolling shutter. In the first case, the entire sensor is activated, while in the second the pixel lines are activated one after the other. Each of these two possibilities offers pros and cons.

Rolling shutter requires a smaller buffer than global shutter, as it does not need to capture all pixels at once, but the installation context must be validated to avoid generating unwanted capture effects, as explained below.

Although it is very common, in certain cases, however, the progressive acquisition of the rolling shutter generates a rather serious defect. In fact, when the sensor or the object in the frame is moving quickly, the image may be distorted.
For example, if a camera is stationary and frames an object moving from left to right, the top of the object will be further to the left than the bottom, which will be further to the right.

This defect is particularly evident when the object or camera moves much faster than the shutter.

When choosing a camera with a global shutter, the required buffer is much larger because all pixels must be captured simultaneously, but there will be no surprises in terms of image distortion.

The figure below simulates a coin captured in motion by a camera with a global shutter (the geometry is respected) and a rolling shutter (visible distortion).

In addition to the type of sensor and shutter, matrix cameras are characterized by their resolution, understood as the size of the sensor and the physical size of the pixel, the data exchange interface (GigE, CameraLink, etc.), the power supply mode and the ability to receive triggers, and other technical details that can make a difference in the design of the vision system.

We offer our customers our experience in designing systems that use the best camera models in terms of functionality and industrial robustness, as you can see in our case histories of vision systems  installed all over the world.