Fast focusing
Focusing and aberration correction with adaptive lenses
Adaptive lenses can improve the performances of established optical systems without the need to completely redesign the instrument. Opto Engineering and Dynamic Optics provide adaptive lenses and wavefront sensor software packages for plug&play experiment and integration inside new products.
Figure 1 | Example of wavefront deformations generated with the M-AL (each panel shows the wavefront, far field in focus, and the interferogram for each aberration). Top row: astigmatism, coma and spherical aberration. Bottom row: trefoil, secondary astigmatism, and quadrifoil. (Figure: Opto Engineering srl)
Fluidic adaptive lenses are present on the market since about ten years ago. Their high degree of modulation of the optical power make them appealing for a series of new applications in autofocus for machine vision, microscopy and medical systems. Opto Engineering established in 2017 a joint venture with Dynamic Optics. One of the first product created is the AO series which is a small Plug&Play device with embedded optics and electronics. Adjusting the focus of a camera on a robot arm, or tracking items across the field of view, are common examples where this focusing is required. The product is a focusing module which can be mounted on the front or on the back of mostly of the fixed focal lenses available on the market to rapidly change focus plane. A range of standard mechanical adapters can be selected to fit the series on mostly of the fixed focal lens available on the market. The series is based on ultrathin glass technology and therefore the gravity does not affect the lens shape when placed with different orientations. The 3.5 diopters allows the user to refocus the lens faster than mechanically moving the lens with traditional motorized solutions. Moreover the actuation time of 1/100th of a second allows the user of creating autofocus algorithms and use the AO series on fast applications. The lens has 23mm clear aperture, making it compatible with a wide range of fixed focal lenses without vignetting. Larger apertures can be developed on request. The built-in electronics gives the product a compact shape without the needs of a separate control. The driver has been specifically developed to accurately control the piezoelectric elements for increased focus accuracy and repeatability. TCP/IP interface through ethernet connection and RS232 through 12-pin Hirose connector are fully compliant with industry standards. A demo user interface with basic control functions is available via a web browser interface. The lens can also be fully controlled with a dedicated .dll library.
Figure 2 | A demo user interface with basic control functions of the AO series is available via a web browser interface. (Figure: Opto Engineering srl)
Aberrations up to the 4th order
Dynamic Optics also presents its unique multi actuator adaptive lens technology that, thanks to its free form optical modulation, extends the application field to aberration correction for obtaining sharper images. The lens can generate aberrations up to the 4th order with stroke comparable to deformable mirrors. Fig. 1 shows the ability of the multi actuator adaptive lens M-AL (NO AOL0223A) to generate arbitrary wavefronts including the aberration of coma that is the main one generated by the gravity effect on polymer lenses. This lens mounts 18 actuators placed outside the clear aperture and therefore the wavefront modulation is obtained without any obstruction or pixel on the light beam optical path.
