Grant Success!

Congratulations to lab member David Wilby on his recently awarded Leverhulme Research Project Grant: Seeing the invisible: the optics of polarization vision. 

David will be moving on from his PhD research in photoreceptor optics to develop our understanding into the optical function of photoreceptors and how they can discriminate the polarization of light. 

Two new papers and a cover from the group

Two new papers in Proceedings of the IEEE have just come out - both on the common theme of biological inspiration in future imaging technologies.


Roberts, N.W., How, M.J., Porter, M.L., Temple, S.E., Caldwell, R.L., Powell, S.B., Gruev, V., Marshall, N.J., and Cronin, T.W. Animal Polarization Imaging and Implications for Optical Processing. Proceedings of the IEEE 102(10), 1427-1434, 2014.

Biologically inspired solutions for modern-day sensory systems promise to deliver both higher capacity and faster, more efficient processing of information than current computational approaches. Many animals are able to perform remarkable sensing tasks despite only being able to process what would be considered modest data rates and bandwidths. The key biological innovations revolve around dedicated filter designs. By sacrificing some flexibility, specifically matched and hard-wired sensory systems, designed primarily for single roles, provide a blueprint for data and task-specific efficiency. In this paper, we examine several animal visual systems designed to use the polarization of light in spatial imaging. We investigate some implications for artificial optical processing based on models of polarization image processing in fiddler crabs, cuttlefish, octopus, and mantis shrimp.


Powell, S.B., Gao, S., Kahan, L., Charanya, T., Saha, D., Roberts, N.W., Cronin, T.W., Marshall, J., Achilefu, S., Lake, S.P., Raman, B., Gruev, Bioinspired Polarization Imaging Sensors: From Circuits and Optics to Signal Processing Algorithms and Biomedical Applications. V. Proceedings of the IEEE  102(10), 1450-1469, 2014.

In this paper, we present recent work on bioinspired polarization imaging sensors and their applications in biomedicine. In particular, we focus on three different aspects of these sensors. First, we describe the electro–optical challenges in realizing a bioinspired polarization imager, and in particular, we provide a detailed description of a recent low-power complementary metal–oxide–semiconductor (CMOS) polarization imager. Second, we focus on signal processing algorithms tailored for this new class of bioinspired polarization imaging sensors, such as calibration and interpolation. Third, the emergence of these sensors has enabled rapid progress in characterizing polarization signals and environmental parameters in nature, as well as several biomedical areas, such as label-free optical neural recording, dynamic tissue strength analysis, and early diagnosis of flat cancerous lesions in a murine colorectal tumor model. We highlight results obtained from these three areas and discuss future applications for these sensors.


A new paper on polarization vision in crustaceans

Journal of Experimental biology has just put up an advance publication of our new paper of polarization vision in fiddler crabs and stomatopods. 

Martin J. How, John Christy, Nicholas W. Roberts and N. Justin Marshall

Null point of discrimination in crustacean polarisation vision  J Exp Biol jeb.103457; First posted online April 15, 2014,  doi:10.1242/jeb.103457

Here's the abstract 


The polarisation of light is used by many species of cephalopods and crustaceans to discriminate objects or to communicate. Most visual systems with this ability, such as that of the fiddler crab, include receptors with photopigments that are oriented horizontally and vertically relative to the outside world. Photoreceptors in such an orthogonal array are maximally sensitive to polarised light with the same fixed e-vector orientation. Using opponent neural connections, this two-channel system may produce a single value of polarisation contrast and, consequently, it may suffer from null points of discrimination. Stomatopod crustaceans use a different system for polarisation vision, comprising at least four types of polarisation-sensitive photoreceptor arranged at 0°, 45°, 90° and 135° relative to each other, in conjunction with extensive rotational eye movements. This anatomical arrangement should not suffer from equivalent null points of discrimination. To test whether these two systems were vulnerable to null points, we presented the fiddler crab Uca heteropleura and the stomatopod Haptosquilla trispinosa with polarised looming stimuli on a modified LCD monitor. The fiddler crab was less sensitive to differences in the degree of polarised light when the e-vector was at -45°, than when the e-vector was horizontal. In comparison, stomatopods showed no difference in sensitivity between the two stimulus types. The results suggest that fiddler crabs suffer from a null point of sensitivity, while stomatopods do not.