Dispersive-based spectrometers may be qualified by their spectral resolving power and their throughput efficiency.
A device known as a virtual slit is able to improve the resolving power by factors of several with a minimal loss
in throughput, thereby fundamentally improving the quality of the spectrometer. A virtual slit was built and
incorporated into a low performing spectrometer (R ~ 300) and was shown to increase the performance without
a significant loss in signal. The operation and description of virtual slits is also given. High-performance, lowlight,
and high-speed imaging instruments based on a dispersive-type spectrometer see the greatest impact from
a virtual slit. The impact of a virtual slit on spectral domain optical coherence tomography (SD-OCT) is shown
to improve the imaging quality substantially.
For optimal performance of a high-precision optical system, careful and stable alignment is necessary. To achieve
robust alignment in a commercial system, performance tradeoffs or significant redesigns are often made. We have
developed subsystems that allow us to automatically monitor and control the optical system alignment, allowing
us to minimize the changes necessary between high-performance research systems and practical commercial
designs. In addition, this can allow ruggedization of systems that would be too unstable otherwise.
We have implemented such an alignment system in a high-performance medical interferometric imaging
device with a focus on maintaining high throughput and allowing for significant system customization. The
system is able to maintain near-optimal alignment without any user interaction over a large thermal range and
can compensate for misalignments during initial system construction or resulting from shock events. With careful
planning, the cost of such a system can be kept reasonably low and it requires minimal interruption to a normal
user's workflow.
We will discuss the basic principles and necessary considerations for the implementation of such a system,
using the developed system as a case study. Similar technology can be used in many optical devices and is
especially relevant if access by a trained technician is difficult or costly.
Laser interference fringe tomography (LIFT) is within the class of optical imaging devices designed for in vivo and ex vivo
medical imaging applications. LIFT is a very simple and cost-effective three-dimensional imaging device with performance
rivaling some of the leading three-dimensional imaging devices used for histology. Like optical coherence tomography
(OCT), it measures the reflectivity as a function of depth within a sample and is capable of producing three-dimensional
images from optically scattering media. LIFT has the potential capability to produce high spectral resolution, full-color
images. The optical design of LIFT along with the planned iterations for improvements and miniaturization are presented
and discussed in addition to the theoretical concepts and preliminary imaging results of the device.
Tissue handling systems position ex-vivo samples to a required accuracy that depends on the features to be
imaged. For example, to resolve cellular structure, micron pixel spacing is needed. 3D tissue scanning at cellular
resolution allows for more complete histology to be obtained and more accurate diagnosis to be made. However,
accurate positioning of a light beam on the sample is a significant challenge, especially when fine spacing between
scan steps is desired or large, inconsistently shaped samples need to be imaged. Optical coherence tomography
(OCT) is an application where accurate positioning systems are required to reap the full benefit of the technology.
By simultaneously manipulating the light beam position and sample location, a 3D image is reconstructed from
a series of depth profiles produced. To automate image acquisition, a fully integrated and synchronised system
is necessary. A tissue handling and light delivery system for free-space optical devices is described. Performance
characteristics such as resolution, uncertainty, and repeatability are evaluated for novel hardware configurations
of OCT. Typical scanning patterns with associated synchronisation requirements are discussed.
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