Custom Lens Design Requirements

High resolution lenses for machine vision — standard and custom lens design

Custom Lens Design Requirements

High Resolution Lenses for machine vision, instrumentation, inspection and vibration-sensitive applications. Standard and custom hi-res lens assemblies.

The last 20 years, system engineers are not requiring custom lenses to meet most customer specifications. Online catalogs, photographic lenses, CCTV products, CCD/CMOS sensor sizes, and various telescope products are offering a large variety of optical combinations. Catalog solutions that fail to meet requirements are due to mechanical space allocation or resolution. If a system engineer has access to a lens designer, then occasionally a combination of catalog lenses can deliver a design to satisfy requirements.

Custom lens designs are necessary to solve the more demanding system requirements, such as military/government/space, special medical instruments, some non-machine vision instruments, and mass produced camera optics. The majority of these systems have unusual resolution, mechanical packaging, or mass pricing that require the involvement of a lens designer. Depending on the experience of the lens designer the effort may last several days to several weeks.

Modern lens design (computer modeling) employs high speed PC’s with multi-processors and professional software that can trace millions of ray surfaces in several seconds will save the company weeks of man-hours. Combine this rapid analysis tool with three to four design texts with classical and modern approaches to starting lens configurations most designers will produce adequate solutions. There are several design areas where specialized experience is required, very low F/# focusing for the semiconductor industry and special instruments, zoom lenses, and designs requiring two or more aspheric surfaces. In these disciplines the starting configurations are extremely important for time savings and minimizing the elements per design.

The typical parameters that system engineers need to recognize that require custom lens design efforts:

1. Combinations of F/# and FOV
2. Resolution higher than 50 lp/mm
3. Wavelength ranges outside the visible
4. Overall lengths that are not in the range of 1.5-2X the EFL
5. No vignetting

As the system engineer is developing optical requirements a few days spent prioritizing parameters and studying what online catalogs have to offer will supply the body of a decision matrix. Armed with this matrix a decision to find a lens designer can be made.