Coherent Microscopy and Optical Coherence Tomography for Biomedical Applications - Bioanalysis Advanced Materials Methods and Devices - page 104

Chapter 8
Coherent Microscopy and Optical Coherence
Tomography for Biomedical Applications
Jeremy M. Coupland and Justin A.T. Halls
Abstract In recent years the traditional, incoherent methods of optical microscopy
have been complemented by coherent imaging methods such as digital holographic
microscopy and optical coherence tomography. These methods have the ability to
image through distorting media, offer extended contrast enhancement modes such
as polarization sensitive and Doppler imaging, and promise varying degrees of 3D
imaging capability. Although these techniques might seem quite disparate both in
configuration and application, they are similar in many important respects.
As coherent, far-field techniques they derive information from the response of the
object to a set of optical stimuli and use interferometric methods to record the phase
and the amplitude of the elastically scattered field at a distant boundary. Hence, it is
only the characteristics of the fields used to illuminate the object and the physical
limitations imposed by the optical systems used to measure the response that
differentiate the various techniques.
In this chapter, the capabilities of coherent microscopy and optical tomography
are compared using linear systems theory. The techniques are characterized in
terms of their 3D transfer functions in the frequency domain and their associated
3D point spread functions in the space domain. It is shown that digital holographic
techniques that reconstruct images from a single, coherent recording of the
scattered field only provide useful 3D information when used to investigate sparse
objects such as cells or particles suspended in a transparent fluid. By synthesizing
images from multiple recordings of the scattered field using different wavelengths
and/or different illuminating wave fronts, the 3D imaging capability of far-field
J.M. Coupland ( * )
Department of Mechanical and Manufacturing Engineering, Wolfson School of Mechanical and
Manufacturing Engineering, Loughborough University, Ashby Road, Loughborough,
Leicestershire LE11 3TU, UK
e-mail: [e-mail]
J.A.T. Halls
Brunel Institute for Bioengineering, Brunel University, Uxbridge, Middlesex UB8 3PH, UK
e-mail: [e-mail]