Close

Search

Search Menu
Photonics Media Photonics Buyers' Guide Photonics Spectra BioPhotonics EuroPhotonics Vision Spectra Photonics Showcase Photonics ProdSpec Photonics Handbook
More News

Lensless Holographic Endoscope Is Self-Calibrated

Facebook Twitter LinkedIn Email Comments
DRESDEN, Germany, Aug. 16, 2019 — Researchers at Dresden University of Technology (TU Dresden) have developed a tiny, self-calibrating endoscope that produces 3D images of objects smaller than a single cell. Without a lens or any optical, electrical, or mechanical components, the tip of the endoscope measures just 200 μm across.

To build a self-calibrating endoscope, the researchers added a 150-μm-thick glass plate to the tip of a coherent fiber bundle (a type of optical fiber that is commonly found in endoscopy applications). The fiber bundle is about 350 μm wide and consists of 10,000 cores.

Tiny, lensless, self-calibrating endoscope, TU Dresden.

Researchers have developed a new self-calibrating endoscope that produces 3D images of objects smaller than a single cell. Courtesy of J. Czarske, TU Dresden, Germany.

When the central fiber core is illuminated, it emits a beam that is reflected back into the fiber bundle. The beam serves as a reference point for measuring the transfer of light. This measurement provides the endoscope with the data it uses to calibrate itself as needed. A spatial light modulator is used to manipulate the direction of the light and enable remote focusing. A camera captures light that is back-reflected from the fiber bundle. The back-reflected light is superposed with a reference wave to measure the light phase.

The position of the beam that is reflected back into the fiber bundle guides the focus of the device, with a minimal focus diameter of about 1 μm. The researchers used an adaptive lens and a 2D galvometer mirror to shift the focus and enable scanning at different depths.

The team tested the new endoscope by using it to image a 3D specimen under a 140-μm-thick cover slip. When scanning the image plane in 13 steps over 400 μm with an image rate of 4 cycles per second, the endoscope successfully imaged particles at the top and bottom of the 3D specimen. However, its focus deteriorated as the galvometer mirror’s angle increased. The researchers said that future work could address this limitation. In addition, using a galvometer scanner with a higher frame rate could allow faster image acquisition.

The minimally invasive device can provide high-contrast imaging and robust stimulation. Its self-calibration capabilities will allow it to tolerate bending or twisting of the fiber. The endoscope could be used in optogenetics to stimulate cellular activity and during medical procedures to monitor cells and tissue.

“The novel approach enables both real-time calibration and imaging with minimal invasiveness, important for in situ 3D imaging, lab-on-a-chip-based mechanical cell manipulation, deep tissue in vivo optogenetics, and keyhole technical inspections,” professor Juergen W. Czarske said.

The research will be presented at the Frontiers in Optics + Laser Science (FIO + LS) conference, Sept. 15-19, in Washington, D.C.

Photonics.com
Aug 2019
GLOSSARY
optogenetics
A discipline that combines optics and genetics to enable the use of light to stimulate and control cells in living tissue, typically neurons, which have been genetically modified to respond to light. Only the cells that have been modified to include light-sensitive proteins will be under control of the light. The ability to selectively target cells gives researchers precise control. Using light to control the excitation, inhibition and signaling pathways of specific cells or groups of...
endoscope
A medical instrument used to view inside the human body by inserting the instrument into a natural or created aperture. The endoscope may use a coherent fiber optic bundle or conventional optics to relay the image to the eye or a television camera. Illumination is provided by a concentric bundle of noncoherent fiber optics.
holography
The optical recording of the object wave formed by the resulting interference pattern of two mutually coherent component light beams. In the holographic process, a coherent beam first is split into two component beams, one of which irradiates the object, the second of which irradiates a recording medium. The diffraction or scattering of the first wave by the object forms the object wave that proceeds to and interferes with the second coherent beam, or reference wave at the medium. The resulting...
Research & TechnologyeducationTU DresdenEuropefiber opticsoptical fibersoptogeneticsopticsendoscopelenslessimagingholography3D imagingOSAThe Optical SocietyFrontiers in Opticsmedicalnano

Comments
back to top
Facebook Twitter Instagram LinkedIn YouTube RSS
©2019 Photonics Media, 100 West St., Pittsfield, MA, 01201 USA, info@photonics.com

Photonics Media, Laurin Publishing
x We deliver – right to your inbox. Subscribe FREE to our newsletters.
We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.