ATLAS: a large array, on-chip compute SPAD camera for multispeckle diffuse correlation spectroscopy.

We present ATLAS, a 512 × 512 single-photon avalanche diode (SPAD) array with embedded autocorrelation computation, implemented in 3D-stacked CMOS technology, suitable for single-photon correlation spectroscopy applications, including diffuse correlation spectroscopy (DCS). The shared per-macropixel SRAM architecture provides a 128 × 128 macropixel resolution, with parallel autocorrelation computation, with a minimum autocorrelation lag-time of 1 µs. We demonstrate the direct, on-chip computation of the autocorrelation function of the sensor, and its capability to resolve changes in decorrelation times typical of body tissue in real time, at long source-detector separations similar to those achieved by the current leading optical modalities for cerebral blood flow monitoring.

Effect of skin color on optical properties and the implications for medical optical technologies: a review.

Significance: Skin color affects light penetration leading to differences in its absorption and scattering properties. COVID-19 highlighted the importance of understanding of the interaction of light with different skin types, e.g.

Development of hydrogel-based standards and phantoms for non-linear imaging at depth.

Significance: Rapid advances in medical imaging technology, particularly the development of optical systems with non-linear imaging modalities, are boosting deep tissue imaging. The development of reliable standards and phantoms is critical for validation and optimization of these cutting-edge imaging techniques.

Aim: We aim to design and fabricate flexible, multi-layered hydrogel-based optical standards and evaluate advanced optical imaging techniques at depth.

Relevance and utility of the and optical properties of the skin reported in the literature: a review [Invited].

Imaging non-invasively into the human body is currently limited by cost (MRI and CT scan), image resolution (ultrasound), exposure to ionising radiation (CT scan and X-ray), and the requirement for exogenous contrast agents (CT scan and PET scan). Optical imaging has the potential to overcome all these issues but is currently limited by imaging depth due to the scattering and absorption properties of human tissue. Skin is the first barrier encountered by light when imaging non-invasively, and therefore a clear understanding of the way that light interacts with skin is required for progress on optical medical imaging to be made.

Application of a wide-field phantom eye for optical coherence tomography and reflectance imaging.

Optical coherence tomography (OCT) and reflectance imaging are used in clinical practice to measure the thickness and transverse dimensions of retinal features. The recent trend towards increasing the field of view (FOV) of these devices has led to an increasing significance of the optical aberrations of both the human eye and the device. We report the design, manufacture and application of the first phantom eye that reproduces the off-axis optical characteristics of the human eye, and allows the performance assessment of wide-field ophthalmic devices.

Validation of human whole blood oximetry, using a hyperspectral fundus camera with a model eye.

Purpose: To assess the accuracy of human blood oximetry measurements in a model eye with a hyperspectral fundus camera.

Methods: Seven human whole blood samples (two arterial, five venous) were obtained, the oxygen saturations measured with a CO oximeter, and the samples inserted into quartz tubes with internal diameters of 100 and 150 μm. The tubes (n = 20; ten 100 μm and ten 150 μm) were placed within a model eye in front of a background reflectance surface with reflectivities of 20%, 60%, and 99%.

Generalization of the Lyot filter and its application to snapshot spectral imaging.

A snapshot multi-spectral imaging technique is described which employs multiple cascaded birefringent interferometers to simultaneously spectrally filter and demultiplex multiple spectral images onto a single detector array. Spectral images are recorded directly without the need for inversion and without rejection of light and so the technique offers the potential for high signal-to-noise ratio. An example of an eight-band multi-spectral movie sequence is presented; we believe this is the first such demonstration of a technique able to record multi-spectral movie sequences without the need for computer reconstruction.