Essential Filters

inVISION: How important are filters for image processing and machine vision?

Georgy Das: Filters are essential for image processing and machine vision in several ways. A bandpass filter, for example, can significantly increase contrast and control the effects of unwanted ambient light, leading to more efficient image processing and ensuring repeatability. Shortpass filters, on the other hand, help create natural color renditions when used with color cameras that don’t have a near-IR cut filter supplied. Protective filters not only provide the precision optical quality required for specific applications but also offer protection from debris, liquids, and other potentially damaging contaminants in challenging environments, depending on the substrate and coatings selected. These examples represent just a small sample of the filter types available, but they illustrate the substantial positive impact that filters can have on machine vision applications.

inVISION: What do I have to pay particular attention to when choosing the right filter for my application?

When choosing the correct filter for an application, it typically comes down to determining which wavelengths need to be passed and which should be blocked, or if another effect is desired, such as reducing specular glare with a polarizer or decreasing transmission with a neutral density filter. It’s also crucial to consider key features like the design of the passband, how the filter performs at higher angles of incidence, and whether the applied coatings are optimized for the useful wavelengths. Ensuring that the filters are inspected for both flawless optical quality and performance is equally important. There are also times when you may need help figuring out where to start. For those situations, I recommend our versatile line of Filter Kits. These kits, such as our brand-new FK201, feature multiple filters with flexible solutions for affixing to lenses with various thread sizes. The Filter Kits also help you test the effects of monochromatic illumination and select the ideal filter for your application.

inVISION: You are currently concentrating on filters. Wouldn’t you like to include lenses in the program?

While it’s not entirely out of the question, we believe our true expertise lies in designing and manufacturing the highest quality filters, protective windows, and custom optics solutions for machine vision and beyond. We have always assisted our customers in designing custom lenses and partnered with lens manufacturers to offer a complete solution. For special projects, we also offer smaller board lenses commonly used in embedded systems, along with the filters that can be mounted or optically cemented for a robust, streamlined solution.

inVISION: Do you also offer solutions for UV and SWIR applications?

Yes, we offer filters for SWIR wavelengths across our Bandpass, Longpass, Polarizers, ND, and Protective filter series. Applications using SWIR wavelengths have been trending for quite some time, and we’re consistently staying attuned to industry developments, continuing to innovate in this wavelength range. We also provide filters well-suited for imaging in the UV spectrum, such as our BP250, BP324, BP340, and BP365. Our BN and Bi series, which feature a narrower passband, are particularly effective if your goal is to use a UV light source to cause the material being inspected to fluoresce, helping to capture the weak emission wavelength. Using a filter for these types of applications ensures you’ll achieve the necessary contrast.

inVISION: What about spectral imaging solutions for drone operations in agriculture?

We offer a line of multi-bandpass filters that are highly effective for agricultural inspections using drones, particularly when calculating NDVI values with a camera equipped with a CMOS sensor. Unlike typical bandpass filters, which have a single passband, multi-bandpass filters feature two or more passbands, enabling you to capture the necessary wavelength channels to calculate NDVI values using the appropriate software. This method allows you to assess the vegetative health of large agricultural areas without the need for full-sized aircraft or costly hyperspectral cameras. It’s a solution that’s become very popular among professionals and hobbyists.

inVISION: Do you have solutions for blue lasers, which are increasingly being used in the metrology sector?

Yes, we offer several bandpass filters with passbands centered on blue wavelengths, including our relatively new BN450. This filter features a narrower passband to help mitigate issues caused by overwhelming ambient light, and it also incorporates our exclusive Stabledge technology. Thanks to its complex coating design, Stabledge allows the filter to be less susceptible to angle of incidence issues, which are common with filters available in the marketplace. This combination makes the BN450 an ideal choice for metrology and other 3D triangulation applications that require the utmost precision when measuring the position, distance, level, displacement, proximity, and profiles of objects.

inVISION: An unusual solution from you is the Backlight Sheets. What’s it all about?

The Backlight fluoresheet, or BF590, is designed to achieve a backlight effect using front illumination. Backlights are typically used to provide sharp contrast to outline shapes, edges, or openings, but space constraints in some applications may limit the use of traditional backlighting. When the fluoresheet is illuminated from the front with a blue LED light, it emits an orange fluorescence. A backlight effect is created by using a MidOpt Orange Bandpass Filter (BP590) to capture the orange emission while blocking the blue LED excitation, resulting in the appearance of a bright white diffuse background in a monochrome image.

inVISION: Which of your solutions are you particularly proud of?

While we’re proud of our entire catalog, our innovative and robust line of Protective Windows is something we’re especially excited about. As machine vision applications are increasingly used in challenging environments – dealing with debris, liquids, fluctuating temperatures, and other factors – the need to protect cameras, lenses, and other expensive components while maintaining a small footprint has become more critical. We take pride in offering these protective windows in multiple substrate types, from high-quality optical acrylic for more budget-conscious solutions to sapphire, which is extremely scratch-resistant while also providing very high optical transmission. These substrates are further enhanced with our hydrophobic and oleophobic coatings, which help prevent the buildup of condensation and keep oils, grease, and fingerprints from collecting on the surface. Customers are even more impressed when they see the customized shapes and sizes we can offer. Our new in-house silk screen printing capabilities allow us to print logos and images directly on the protective window, creating a truly customized solution. Additionally, the ability to add strong adhesive backings to these windows makes mounting them to an enclosure or other surface incredibly easy.