Focal Length, Field of View, and Sensor Size
Focal length does not determine field of view by itself. Sensor dimensions, object distance, distortion, and finite-conjugate magnification also matter. Start from the required object field and detector format, then solve the geometry and confirm that the lens maintains resolution and illumination across that field.
Why this decision matters
This choice affects more than nominal optical performance. It changes package volume, tolerance sensitivity, supplier options, alignment effort, calibration, test equipment, production yield, and the evidence required before release. The correct answer therefore comes from the complete operating condition and acceptance method, not from a single catalog value.
Key engineering decisions
- Define horizontal, vertical, and diagonal field at the actual working distance.
- Choose sensor format and pixel pitch from sampling and package needs.
- Budget distortion and chief-ray angle before fixing focal length.
These decisions should be captured in a requirement or trade study before the team commits long-lead components. Where requirements conflict, rank the product priorities explicitly so optimization does not hide a business decision.
Specification checklist
- Object field dimensions
- Working-distance range
- Sensor active area
- Allowed distortion
- Image circle and relative illumination
Every value should state the condition where it applies and how it will be measured. A specification without a defined test condition is not yet an acceptance requirement.
Common failure mode
A lens is selected from a simple infinity-conjugate calculator, then misses field or focus after the real object distance, cover glass, and distortion are included.
The practical remedy is to compare the nominal model, tolerance prediction, mechanical interfaces, and measured configuration together. Treating the symptom as an isolated lens or component problem often produces another build with the same system-level limitation.
Verification approach
Image a dimensional target at minimum, nominal, and maximum distance; measure field, distortion, focus, and corner illumination.
Record the hardware revision, source or scene, wavelength, aperture, field point, focus or alignment state, environmental condition, processing, and measurement uncertainty. This makes the result useful for design iteration and supplier transfer rather than only for a one-time demonstration.
What to send PAO
Send object dimensions, working distance, sensor, package envelope, field margin, distortion limit, and representative scene images.
PAO applies this framework through custom optical design, from requirements and architecture through detailed design, prototype evidence, and manufacturing transfer.