The Core Aspect of Telecentric Lenses - Wavelength

The Core Aspect of Telecentric Lenses - Wavelength

Designing optical systems is complex; even a perfectly designed system can have optical aberrations. The design of telecentric lenses is particularly challenging because it requires near-perfect elimination of these aberrations to create an optimal telecentric lens.

Optical Aberrations and their Origins: Optical aberrations refer to deviations from the perfect mathematical model. They don't stem from physical, optical, or mechanical defects but from the lenses themselves, or the placement of optical components within the system. The ultimate cause is the wave nature of light. In paraxial optical designs, aberrations are often ignored because they consider light as rays, but in telecentric systems, the wave properties must be accounted for.

Monochromatic Illumination and Aberration Reduction: Monochromatic illumination can improve contrast by eliminating longitudinal chromatic aberration (color focus shift) and transverse chromatic aberration. Monochromatic lighting can be achieved with LEDs, lasers, or filters. However, different wavelengths can impact Modulation Transfer Function (MTF) in a system. The diffraction limit, based on the definition of the Airy disk diameter, is also wavelength-dependent, impacting the smallest spot a perfect lens can theoretically produce.

Challenges in Telecentric Lens Design: As the wavelength decreases, the design complexity increases, with more blue spectrum light entering the system. This increase in design difficulty occurs regardless of the bandwidth used. Glass materials tend to perform poorly at shorter wavelengths. Although certain designs can mitigate chromatic aberrations within a spectrum range, these are often limited in effectiveness unless special and costly materials are used. This is why telecentric lenses are expensive; the cost of these specialized materials and the precision required for their design contribute to their high price.