Shortwave infrared (SWIR) imaging is increasingly employed in food and food packaging applications to detect discrepancies across the food and beverage sector. This article looks at how the technology works and the roles played by lighting and filters in further enhancing the functionality of this popular machine vision solution.
How SWIR Works
SWIR imaging leverages low-frequency light, allowing it to observe objects much differently than a traditional visible light camera. SWIR cameras can effectively penetrate plastic and many other liquid materials, affording SWIR machine vision systems a definitive advantage over VIS-NIR systems for detecting food quality.
Using quality optical filters with SWIR technology enhances contrast, improving machine vision applications’ reliability.
Filters feature a bandpass that controls which wavelengths are allowed to pass through them and which wavelengths are blocked.
Conventional color filters offer a single bandwidth and a less effective passband shape. However, advanced sputter-coated filters allow image capture over single or multiple bandwidths with no loss in resolution or contrast. Sputter-coated filters are compatible with various vision systems, including SWIR, resulting in improved contrast even when used in environments with high-frequency or bright light sources.
Fig. 1. Sputter-coated filters provide the best combination of brightness and contrast for machine vision. Image Credit: Chroma Technology Corp.
LED Advances Accelerate Machine Vision
LED technology has improved in recent years in terms of cost, efficiency, and output intensity, and LED lighting is beginning to replace traditional lighting sources in many settings.
Compact, integrated LED arrays now have longer lifespans, provide more intense light, and even accommodate shorter strobe on/off cycles. Conventional lights, such as halogen or incandescent bulbs, require longer to reach full intensity and turn off, but LEDs can complete this cycle orders of magnitude faster.
Their capacity to rapidly cycle on and off at great intensities has led to the development of light arrays able to strobe over 100,000 times a second with 10 times the output of some conventional lighting solutions.
Settings like food and beverage plants are seeing increasing demand for machine vision systems that can operate accurately and repeatedly at high speeds. These capabilities are key to reducing lead times and increasing production rates.
Machine vision systems are also evolving to accommodate ever-more complex tasks. Automating food inspection and sorting tasks typically involves a great deal of cost because capturing the data required to maintain quality without negatively impacting production speeds can be difficult.
LED and filter technologies have advanced while simultaneously reducing their barrier to entry, resulting in more accessible machine vision solutions such as SWIR.
Better-Tasting Food with Filters and SWIR Technology
Meat inspection is another popular SWIR application in which integrators in the food industry leverage powerful SWIR LEDs and grayscale InGaAs cameras fitted with sputter-coated filters to determine meat’s grade, age, damage, disease, and bone location.
This technology produces data that can be combined with basic arithmetic to produce an image that accentuates bone and various tissues in high contrast. These are all key factors in ensuring food safety.
Organizations like the United States Department of Agriculture (USDA) employ grading systems to rank the quality of marbling—the ratio of muscle and fat—in meat. This is typically associated with the product’s overall flavor and quality.
Accurately capturing marbling data ensures cost-effective, unbiased food grading and inspection. Using an automated vision system that can inspect, grade, and detect specific features in meat of any kind ensures that the final meat product is appropriately graded in line with USDA standards.
A high degree of food inspection also allows companies to charge premium rates for high-end cuts of meat.
Fig. 3. A typical InGaAs SWIR camera offers the sensitivity to capture food data accurately. Image Credit: Chroma Technology Corp.
Attenuating Unwanted Light
Conventional filters feature a Gaussian bandpass shape, and a color filter’s lazy slope allows more unwanted light or noise into an image. Therefore, it is important to reduce unwanted light as much as possible, as vision applications are required to perform more complex tasks at higher speeds.
Sputter-coated filters feature a square bandpass shape that can refine the range of wavelengths allowed through the system.
In an ideal machine vision environment, only the light sources required to detect desired objects and features should be present. Ambient light, windows, and lasers could potentially interfere with imaging systems.
While it is unrealistic to expect an environment to be entirely free of unwanted light, the square bandpass shape of sputter-coated filters such as Chroma’s ContrastMax allows them to attenuate up to 95 % of unwanted light. Sputter-coated filters from a good manufacturer will employ a single light source and camera to capture single or multiple bandwidths with compromise in image contrast of resolution.
Working with advanced lighting in machine vision, SWIR, and sputter-coated filters can simultaneously inspect products for bruises, damaged packaging, and other defined characteristics while providing the required information to guide automation equipment for inventory or related sorting processes.
Food and beverage companies can also depend on the accuracy and reliability of SWIR machine vision systems fitted with sputter-coated filters to enhance existing systems, postponing or eliminating the need for costly upgrades.
Should a new vision system be needed, existing sputter-coated filters and advanced lighting can compensate for less advanced and more affordable lenses and cameras. This allows companies to meet their quality and production goals while lowering costs and improving ROI.
Fig. 4. Sputter-coated filters have a square bandpass shape that can hone the range of what wavelengths it lets through the system. The ContrastMax filter passbands shown are centered on the peak wavelengths of common LEDs. Image Credit: Chroma Technology Corp.
Automating the Food Industry’s Future
Chroma’s manufacturing capabilities have enabled the company to build tolerances into sputter-coated filters for single or multiple bandwidths, enhancing machine vision accuracy and reliability while reducing the number of false reads.
Sputter-coated filters can accurately accept and block single or multiple bandwidths, but machine vision systems must not rely entirely on outside lighting sources. Machine vision applications must leverage a dedicated lighting system to ensure the imaging system’s capabilities are not reduced.
Leveraging a robust combination of SWIR, Chroma’s sputter-coated filters and appropriate lighting allows powerful machine vision systems to simultaneously drive quality inspections and automation controls from a single light source and camera.
Constraints across the food industry are prompting a need for automation and vision systems that can improve production and limit costs while maintaining or enhancing quality.
As global populations continue to grow, there is increasing concern about the food and beverage sector’s capacity to rapidly and effectively produce quality food. Technologies such as machine vision represent an ideal means of enabling automation while accelerating manufacturing production.
Machine vision can improve food safety and enhance profits via inspection and the rapid detection of features such as prime cuts of meat without disrupting production flow. Using a combination of SWIR machine vision systems and sputter-coated filters allows the food industry to expand its capabilities while ensuring the safety and quality of the food on tables and beyond.
Acknowledgments
Produced from materials originally authored by Chroma Technology Corp.
This information has been sourced, reviewed, and adapted from materials provided by Chroma Technology Corp.
For more information on this source, please visit Chroma Technology Corp.