Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) is a powerful tool for retinal imaging at a cellular level. In conventional AOSLO, a pinhole conjugate to the retinal plane is used to reject out-of-focus light. This pinhole enables resolution improvement compared to standard bright-field microscopy imaging; however, the maximum resolution improvement can only be achieved when the pinhole is very small compared to the system’s point spread function. Thus, in practice one must find a compromise between the system’s achievable resolution and light throughput, which dictates the signal-to-noise ratio (SNR). In retinal imaging SNR is of high importance since the amount of light is limited by safety regulations.
We introduce a new detection scheme into AOSLO using a similar technique to that recently developed for confocal scanning microscopy. Here we replace the single element pinhole detector with a multi-element design. This multi-element detector consists of a multimode fiber bundle with seven fibers, where the fiber tips are arranged in a closely-spaced hexagonal pattern on one side and are completely separated on the other side and each fiber is attached to a detector. Each of the fibers acts as a pinhole recording an image which is shifted with respect to the center fiber’s image. By aligning the images of the individual fibers and consolidating all of the light collected, an enhanced image with improved SNR can be processed.
Thus, this design enables better SNR, without sacrificing resolution or altering imaging conditions. To demonstrate the capabilities of our system, we present phantom sample images.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon