German technology has yet again taken a great leap towards another ground-breaking innovation in imaging and printing as it launched its newest imaging tool no larger than a grain of salt.
Researchers at the University of Stuttgart have developed a miniature camera using a new 3D printing technique. Experts say the ingenious technique provides sub-micrometer accuracy that enables users to 3D print optical systems containing four lenses. The resulting multi-lens system provides an opportunity to help correct aberration, a condition where lenses fail to bring all wavelengths of color to a single focal point, which in turn may facilitate higher quality imaging from smaller devices, researchers added.
The researchers developed the 3D lenses by blasting a light-sensitive material onto a glass substrate with a femtosecond laser, which has pulse durations shorter than 100 femtoseconds. The material then absorbed two photons that exposed it and crosslinked polymers within the material. The unexposed material was washed using a solvent, leaving the hardened, crosslinked polymer that will then serve as the optical element.
The resulting lens’ diameter measures about 120 millionths of a meter, which makes it easily as small as a grain of table salt. The lenses can go from wide to narrow and may provide low to high image resolutions. Each of the lenses has a specific line of sight – clear at the center, blurry at the sides – capped by a curvature at the end. This mechanism mimics how the fovea, the small depression in the middle of the retina, collects light, and how the brain connects images from both eyes to come up with a single, distinct picture.
The innovative method will enable a variety of designs to undergo testing to come up with high-quality images. Researchers also noted that because it is printed in one piece the lens is easier to configure. Any configuration that was designed on a computer can be readily printed and used, researchers stated. The lens can also be printed onto image sensors aside from fiber optics.
The imaging method allowed researchers to print components for optical microscopes measuring 125 micrometers, and attach them to a 1.7m thin optical fiber. The camera at the end of this small endoscope has the capacity to focus on images from a distance of 0.12 in. The entire imaging system fits perfectly inside a syringe needle, which opens possibilities for direct delivery to various organs including the brain. Researchers said future uses of this highly miniaturized camera system may include less-invasive body imaging.
Experts cite initial limitations of the camera
To further assess the various applications of the lens, the developers also printed it onto a CMOS image chip in order to come up with a tiny sensor. Researchers noted that the manufacturing mechanism was fast, and may eventually translate into smaller camera drones. “The time from the idea, the optics design, a CAD model, to the finished, 3D-printed micro-objectives is going to be less than a day. We are going to open potentials just like computer-aided design and computer-integrated manufacturing did in mechanical engineering a few years ago,” said Professor Harald Giessen, from the University of Stuttgart’s 4th Physics Institute.
“Further improvements would include antireflection coatings on the lenses, either by coatings or by nanostructuring; the use of triplets or more lens elements for aberration correction; and the inclusion of absorbing aperture stops. With fabrication times of 1 to 2 hours for one objective lens, cheap high-volume manufacturing is difficult at the moment. However, printing just the shell and a lamellar supporting frame and direct ultraviolet curing can reduce the fabrication time… ” researchers added.
The research was published in the Nature Photonics journal.