1. The Electromagnetic Spectrum

The electromagnetic specturm consists of all the known wavelengths of light.

Above: The electromagnetic spectrum. The approximate scale of wavelength yields a rough idea of the smallest obect that canbe detected using that part of the spectrum

Please note that the part of the spectrum that comprises the visible portion of light is very small with respect to the entire spectrum. And, with respoect to machine vision we typically use that portion of the spectrum from the near infrared to ultraviolet. We describe these wavelengths typically in nanometer scale.

Above: The primary portion of the spectrum used by machine vision CCD or CMOS imaging sensors, expressed in nanometer wavelengths.

2. Basic Machine Vision Camera

Let's look at a basic machine vision camera. Here is a camera without a lens.

Above: typical machine vision camera

Let's look inside this camera to see the typical components: the front end printed circuit board with an imaging sensor and the back end PCBs with various purposes.

Above: Internal to the machine vision Camera will be the imaging sensor and back end circuitry boards

Logic in the back end circuitry will comprise numerous functionality -

•   A/D converters
•   Amplifiers
•   Clocks for exposure & frame rate
•   Read out circuits
•   FPGAs
•   Memory
•   others functions

2.1. Imaging Sensors

Visible light sensors

The most common visible light imaging sensors are:

• Silicon CCD, charge coupled device or,
• Silicon CMOS, Complementary metal oxide semiconductor

Infrared sensors typically come in either cooled or uncooled versions. Below are some examples along with the wavelengths of light they are designed to detect.

Cooled Infrared Sensors

•   Indium gallium arsenide InGaAs (1-2 μm wavelength)
•   indium antimonide (3-5 μm wavelength)
•   indium arsenide
•   mercury cadmium telluride (MCT) (1-2 μm, 3-5 μm, 8-12 μm wavelength)

• lead sulfide
• lead selenide

UnCooled Infrared Sensors

•    amorphous silicon (a-Si)
•    vanadium(V) oxide (VOx)
•    lanthanum barium manganite (LBMO)
•    lead zirconate titanate (PZT)
•    lanthanum doped lead zirconate titanate (PLZT)
•    lead scandium tantalate (PST)
•    lead lanthanum titanate (PLT)
•    lead titanate (PT)
•    lead zinc niobate (PZN)
•    lead strontium titanate (PSrT)
•    barium strontium titanate (BST)
•    barium titanate (BT)
•    antimony sulfoiodide (SbSI)
•    polyvinylidene difluoride (PVDF)