Volume holographic imaging endoscopic design and construction techniques

Abstract

Abstract. A reflectance volume holographic imaging (VHI) endoscope has been designed for simultaneous in vivo imaging of surface and subsurface tissue structures. Prior utilization of VHI systems has been limited to ex vivo tissue imaging. The VHI system presented in this work is designed for laparoscopic use. It consists of a probe section that relays light from the tissue sample to a handheld unit that contains the VHI microscope. The probe section is constructed from gradient index (GRIN) lenses that form a 1:1 relay for image collection. The probe has an outer diameter of 3.8 mm and is capable of achieving 228.1 lp∕mm resolution with 660-nm Kohler illumination. The handheld optical section operates with a magnification of 13.9 and a field of view of 390 μm × 244 μm. System performance is assessed through imaging of 1951 USAF resolution targets and soft tissue samples. The system has also passed sterilization procedures required for surgical use and has been used in two laparoscopic surgical procedures.

Optical Measurement of Ligament Strain: Opportunities and Limitations for Intraoperative Application

“…The methods described in [45,[47][48][49][50]55,56,58,59] do not meet the requirements for the measurement accuracy. Those described in [51,56,59,60] have an insufficient FoV for the planned application.…”

“…The methods described in [43,45,[51][52][53] are unsuitable for the analysis of displacement vectors. Nevertheless, the holographic endoscopic system described in [50] meets the minimal requirement regarding the measurement accuracy. The applicability of the holographic system is discussed in Section 4.2.…”

Wavelength-coded volume holographic imaging endoscope for multidepth imaging

“…Introduction of volume holographic imaging (VHI) techniques, a method analogous to slit scan confocal microscopy, has shown the capability of simultaneous multidepth imaging. [3][4][5][6] VHI imaging removes the need for mechanical scanning through the use of multiplexed volume holographic elements. [7][8][9][10][11][12][13][14][15] Of particular interest in the development of VHI systems is the use of wavelength-coded methods to address the issue of contrast reduction caused by the hologram channel crosstalk and hologram Bragg degeneracy properties.…”

“…This is an improvement in lateral resolution from the reflectance endoscope system that had a resolution of 4.2 μm using curved fringe holograms with the other optics being the same. 6 Biological samples were used to evaluate imaging depth performance when a tissue volume was illuminated. The resulting images, shown in Fig.…”

“…In summary, initial results indicate that the WC endoscope utilizing an axial chromatic dispersion system is capable of multifocal imaging with greater resolution than the single wavelength reflectance system. 6 The 100-μm difference in image depth is large enough to view variations in the cellular structure of onion skin as well as animal tissue samples such as mouse fat. In addition, the evaluation of lower contrast tissue samples, such as lung and intestine samples, shows significant loss of image feature characteristics at depths of 100 μm due to the lack of background rejection within the image channel due to Bragg degeneracy of the hologram and unstructured illumination.…”