This introductory lecture will cover the basic physics of light and the use of lenses to both form an image of an object and to illuminate it. A Fourier-based description of microscopes will be given to help give a conceptual understanding of microscopy and its limitations. Finally a brief introduction will be given to concepts that will be covered in more detail later in the course including fluorescence imaging, light sources and detectors.

    We tend to think of microscopes as having a high numerical aperture, in that they typically collect light from a sample over as wide a range of angles as possible. This is often necessary to achieve good depth resolution, to maximise the light collection efficiency, or both. However, there is also usually a requirement for high magnification, which reduces the numerical aperture at the detector in proportion. The problem we address here is that the illumination pathway, being basically the reverse of the detection one, will also have a low numerical aperture, so the situation for the light source is rather like having to shine light through a tunnel. Both the theoretical and practical challenges of this requirement are discussed, together with a discussion of the various practical solutions.

Cairn Research Ltd is an independent optical instrumentation Company, founded by Martin in the dim and distant mists of the 1980s. Our primary activity is the design and sale of products for the detection and measurement of optical fluorescence. We are based on our own farm just outside Faversham in Kent, where Martin continues to design ever weirder and more wonderful products for the Company, of which the accompanying photo happens to show one such.. However in this activity he now has the support of many others, including our CEO Jeremy Graham who will be giving a talk on camera technology later in this course.

    Among the various fluorescence microscopy methods, fluorescence lifetime imaging (FLIM) has emerged as a key technique to image the environment and interaction of fluorophores in living cells.[1] The contrast in FLIM images is given by the fluorescence lifetime of the fluorophores, independent of their concentration.[2] I describe what fluorescence is, highlight the significance of the fluorescence lifetime, then give some examples of FLIM measurements and point to future developments. 

 [1] S. Ameer-Beg, K Suhling, M. Kuimova, Special issue on fluorescence lifetime imaging (FLIM): from fundamentals to applications‎, Methods Appl Fluoresc 8(4), 040401, 2020. 

[2] K. Suhling, L.M. Hirvonen, J.A. Levitt, P.-H. Chung, C. Tregidgo, A. Le Marois, D. Rusakov, K. Zheng, S. Ameer-Beg, S. Poland, S. Coelho, R. Henderson and N. Krstajic. Fluorescence Lifetime Imaging (FLIM): basic concepts and some recent developments, Medical Photonics 27, 3-40, 2015. 

    In the last 35 years, optical imaging has become one of the most important applications of the laser. This lecture will give an overview of how lasers work, description of key parameters of lasers relevant for biomedical imaging, considerations when choosing lasers for imaging studies, and some applications of lasers in one- and two-photon microscopy.

    Since I last presented this talk in 2019, digital cameras for biological light microscopy have achieved near-perfection for most applications.  Huge investment and innovation led by the mobile phone industry, and others, has produced sensors that have overtaken the resolution and field-of-view limits of the objective lens with close to 100% efficiency and high dynamic range. So what next?
In my talk I will present an overview of current scientific camera technologies and some thoughts on possible future developments…

As CEO of Cairn Research Ltd I am immersed in the interface between technologists and scientists, and privileged to learn from both, which, hopefully, helps enable our company to build effective solutions to novel and existing microscopy challenges. Historically we have been associated with physiological fluorescence imaging, but are now involved in numerous projects across the micro and macro bio-imaging worlds.