Functional monitoring of highly-localized deep brain structures is of great interest. However, due to light scattering, optical methods have limited depth penetration or can only measure from a large volume. In this research, we demonstrate continuous measurement of hemodynamics in different cortical layers in response to thalamic deep brain stimulation (DBS) using a single fiber optical system. A 200-μm-core-diameter multimode fiber is used to deliver and collect light from tissue. The fiber probe can be stereotaxically implanted into the brain region of interest at any depth to measure the di
use reflectance spectra from a tissue volume of 0.02-0.03 mm<sup>3</sup> near the fiber tip. Oxygenation is then extracted from the reflectance spectra using an algorithm based on Monte Carlo simulations. Measurements were performed on the surface (cortical layer I) and at 1.5 mm depth (cortical layer VI) of the motor cortex in anesthetized rats with thalamic DBS. Preliminary results revealed the oxygenation changes in response to DBS. Moreover, the baseline as well as the stimulus-evoked change in oxygenation were different at the two depths of cortex.
Compound eye lens (CEL) is expected to be applied in high-speed object tracking and depth perception. However, it is difficult to fabricate CEL due to the complex shape and structure. We study its mathematic and optical model. Based on the established model, a grid machining method is proposed for the fabrication of a CEL mold. To avoid the shape distortion caused by tool un-alignment, the off-centering machining configuration is proposed, which is also proved to improve the form accuracy. CEL is machined finally by molding technologies using the fabricated mold to avoid the tool interference. Experiments have been implemented to verify the design and fabrication method. The shape accuracy evaluation and optical testing are conducted to prove that the proposed method can be applied well for the machining of CEL.