How SWIR Technology With
Sputter-Coated Interference
Filters Helps Determine
Food Quality
Sputter-Coated Interference Filters Help SWIR Machine Vision Systems
Advance Automation for the Food Industry

For the food and beverageindustry, shortwave infrared(SWIR) imaging is being
adopted for food and foodpackaging applications todetect discrepancies. The
following introduces how thetechnology works and therole lighting and filters play inadvancing the benefits of thismachine vision solution.

than a visible camera would. For example, SWIR

LED Advances Accelerate Machine Visionand making machine vision solutions such ascameras can see through plastic and various

As LED technology has improved in cost,

SWIR more accessible.

How SWIR Works

high-frequency or bright light sources, sputter-liquid materials, which gives SWIR machine visionsystems a major advantage over VIS-NIR systems
to detect food quality.
Implementing quality optical filters with SWIR
technology improves contrast for better reliability
in machine vision applications. Filters have a
bandpass that determines which wavelengths
it will let through and which it will block. While
traditional color filters offer a single bandwidth,and a less effective passband shape, sputtercoated filters can capture images over single ormultiple bandwidths without suffering losses incontrast or resolution. Even in environments withcoated filters work with various vision systems,

SWIR imaging uses low-frequency light that

including SWIR, resulting in improved contrast.

allows it to see many objects much differently

efficiency, and output intensity, LED lighting
has replaced traditional lighting sources. Small,Better-Tasting Food With Filters and SWIR

integrated LED arrays are lasting longer, providing

Technology

more intense light and even shorter strobe on/off

Other SWIR applications include meat inspection.

cycles. Traditional lights such as incandescentor halogen bulbs take more time to reach fullintensity and turn off, while LEDs can complete
this cycle orders of magnitude faster. The ability
to cycle on and off quickly at great intensities hascreated light arrays capable of strobing more than
100,000 times a second with 10 times the output
of some traditional lighting solutions.
Demand is growing for machine vision systems
that can operate accurately and repeatedly at highspeeds in settings such as food and beverage
plants, reducing lead times and increasing
the rate of production. Additionally, machine
vision systems are evolving to incorporate more

100complex tasks into their capabilities. Automating
food inspection and sorting tasks can be costly

90
80

because it’s difficult to capture the data necessary

Sputter-coatedinterference filters

Colored glass filter

to maintain quality without disrupting production
speeds. Fortunately, LED and filter technologies

70

Transmission (%)

have advanced while reducing the barrier of entry
60

Integrators in the food industry are using SWIR
LEDs and grayscale InGaAs cameras outfitted with
sputter-coated filters to determine the age, grade,damage, disease, and bone location in meat. In
addition to ensuring food is safe, this technology
produces data that, when combined with basicarithmetic, can produce an image accentuatingbone and various tissues in high contrast.
The USDA and other organizations use grading
systems to rank the quality of marbling in meat.
Marbling — or the ratio of fat and muscle in meat
— is associated with the flavor and quality of theproduct. Accurately capturing marbling data canensure cost-effective, unbiased food grading andinspection. An automated vision system’s ability
to inspect, grade, and detect specific features inany type of meat ensures that product is properly
USDA graded. Additionally, this level of foodinspection gives companies the ability to charge
premium rates for high-end cuts.

50LED spectral
output4030
201001100

1300

1500

Wavelength (nm)1700

Fig. 1. Sputter-coated filters provide the best combination of brightness and contrast for machine vision.

1900

Fig. 2. A bruise on a piece of fruit will show up on a SWIR image as a black mass due to its water content.
Courtesy of Smart Vision Lights

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SWIR Camera Sensitivity
1Camera QE

0.8

0.6

0.4

0.2
1800

0800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

Wavelength (nM)
C12741-11 (cooled)

C12741-03 (uncooled)Fig. 3. A typical InGaAs SWIR camera offers the sensitivity to accurately capture food data.

Attenuating Unwanted Light
Traditional filters have a Gaussian bandpass
shape. The lazy slope of a color filter allows moreunwanted light, or noise, into an image. With visionapplications evolving and being asked to do more
complex tasks at higher speeds, it is imperative
to reduce as much unwanted light as possible.
Sputter-coated filters have a square bandpass
shape that can hone the range of what wavelengths
it lets through the system. In an ideal machine
vision environment, no other light sources would bepresent other than what is needed to detect desired
objects and features. Ambient light, windows, andeven lasers can interfere with imaging systems.
While an environment free of unwanted light is notrealistic, sputter-coated filters such as Chroma’sContrastMax attenuate up to 95% of unwanted lightlargely due to their square bandpass shape.

Additionally, sputter-coated filters from leading
manufacturers can use a single lighting source andcamera to capture single or multiple bandwidths

Fig. 4. Sputter-coated filters have a square bandpass shape that can hone the range of what wavelengths it lets throughthe system. The ContrastMax filter passbands shown are centered on the peak wavelengths of common LEDs.

existing sputter-coated filters and advanced

automation controls at the same time from a single

lighting can compensate for less advanced

light source and camera.

and more cost-effective cameras and lenses.
Companies meet quality and production goals

Constraints in the food industry are driving trends

while reducing cost and improving ROI.

in automation and vision to increase production
and reduce cost while maintaining or improving

Automating the Food Industry’s Future

without compromising image resolution orWith Chroma’s manufacturing capabilities, itcontrast. With advanced lighting in machine vision,is possible to design tolerances into sputter-

SWIR and sputter-coated filters can simultaneously

coated filters for single or multiple bandwidths toinspect products for damaged packaging, bruises,

increase machine vision accuracy and reliability

and other characteristics while providing theand reduce false reads. Despite the ability of

information necessary to guide automation

sputter-coated filters to accept and block single orequipment for inventory or sorting processes.

multiple bandwidths accurately, it is still importantthat machine vision systems do not completelyFurthermore, food and beverage companies

rely on outside lighting sources. Machine vision

can rely on the capability and accuracy of SWIR

applications should have a dedicated lighting

machine vision with sputter-coated filters tosystem to ensure an imaging system’s capabilities

improve machine vision systems already in place,are not diminished. With SWIR, Chroma sputter-delaying or even eliminating the need for expensive

coated filters, and the right lighting, machine

upgrades. If a new vision system is needed, thevision systems can drive quality inspections andquality. As the population grows, producing quality
food effectively and quickly is an increasing
concern. Technologies such as machine vision
improve automation and accelerate manufacturing
production. Machine vision increases food safety andprofits through inspections and detecting features
such as prime cuts of meat quickly without disrupting
the flow of production. SWIR machine vision systems
and sputter-coated filters expand the capabilitiesof the food industry while ensuring the safety andquality of the food on your table and beyond.
For more information about sputter-coatedfilters for SWIR machine visionsystems, please contact us today.

5

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Dec 2021