Control 2017 Telecentric lenses with focus tunable lenses
Germany – In co-operation with Swiss-based Optotune, Sill Optics has designed telecentric lenses, which includes a focus-tunable lens, that can adapt the focus with changing working distances.
In many industrial inspection applications, different object heights have to be measured. For this, object-sided telecentric lenses with constant magnification for the entire depth of field are recommended. To increase the useable depth further, defocusing is necessary to maintain the required resolution.
According to the company, the electrically tunable liquid lens EL-16-40-TC with a refractive power of -3.0 to +3.5 diopters was initially combined with the company's current 2-time-magnifying telecentric lens. Within milliseconds, different heights or working distances can be measured reliably and reproducibly. It’s possible to reach a maximum working distance change of about 13 mm because the power can be adjusted in the device. The magnification varies thereby by approximately +/- 3% along the working distances. The working distance as well as the magnification show a linear dependence on the optical power of the lens. Thus, the influence of the measurement results can be eliminated by calibrating the measurement system. Additionally, a distortion error of less than 1% and a telecentric error of less than 0.1% are achieved. The evaluation of the first prototypes show a very good image quality even in the field of edges, the company says. Because all design parameters can be confirmed by measurements, new application fields are now possible with the telecentric lenses.