The importance of polymer optics in machine vision

Machine vision for position control or data retrieval can be found in a variety of different applications and industries. Autonomous passenger or fleet vehicles, automated warehousing, automated production facilities, robotics, or bar code readers all use “machine vision”. This may take the form of actual camera imaging systems, “time of flight” systems such as LiDAR, or simultaneous localization and mapping (SLAM) based LiDAR or similar technologies. Almost all autonomous passenger/fleet vehicles are using a combination of imaging systems and LiDAR.

Product managers responsible for bringing new machine vision products from inception through prototyping to market will be challenged with:

• Technical challenges - Does the system perform to specification?
  • Can the assembly be simplified and the Bill of Material (BOM) cost reduced
  • Are mounting features required for the optics?
• Timing constraints - It is imperative to get the product to market ahead of the competition!
• Pricing challenges - Bill of material (BOM) price must be low enough to charge fair market value for the system while providing strong revenue and profitability for the company.

Technical challenges

From a technical perspective, polymer optics are an excellent candidate for meeting the specification requirements associated with machine vision, especially in LiDAR and industrial automation systems.

• The general spectral band of interest is well-within the realm of excellent transmission for polymer optics.
• If reflectivity is required, polymer optics readily accept coatings including aluminum, silver, and gold with protective layers as well.
• Polymer optics weigh less than glass optics, potentially allowing the system to be designed with less mass.
• One of the most important areas of concern when designing with polymer optics would be extreme thermal transients. For example, if designing for imaging, the designer must consider the significant change in the refractive index of the substrate with temperature (dN/dT).
• The complexity of any assembly drives cost. If the number of discreet parts comprising an assembly is reduced without increasing the the discreet part design the assembly complexity is reduced and the BOM cost is reduced. In many instances this may be addressed by including mounting features on plastic optics. Additionally, the number of elements required in a lens may be reduced through the introduction of aspherical elements.

Timing constraints

Rapid proof of concept and prototyping can take place well in advance of the mold completion permitting high volume production within weeks while the mold is being manufactured through the use of:

• Direct single point diamond machining of the optic from a “blank” of the chosen material
• A prototype mold to produce a small pre-production run

Pricing challenges

Injection molding processes are capable of producing high volumes of identical optics resulting in low unit costs. As previously stated, mounting features may be incorporated into the optics resulting in additional BOM reductions and reduced overall manufacturing and assembly costs.

Injection molded polymer optics are an excellent option to address these concerns. It is imperative that your design team contact a skilled and experienced optical plastic injection molding company as early in the design phase as possible to ensure the advantages and limitations of injection molding are fully understood during system design.