638
S. P. Singh and S. Siddhanta
by Antoine van Leeuwenhoek. In the 1800 and early 1900, rapid developments
started taking place with the development of ‘ophthalmoscope’ by German scientist
Hermann Ludwig Ferdinand von Helmholtz [1]. This was followed by the invention of the maser (microwave amplification by stimulated emission of radiation) in
1954 which was the predecessor of Laser discovered by Charles Townes and Arthur
Schawlow, although the concept of stimulated emission was introduced by Albert
Einstein in 1917. The advent of the first solid-state laser by Theodore H. Maiman
added a new dimension to the field of optics. The development of important concepts
such as diffraction demonstrated by Thomas Young, polarization by Etienne Louis
Malus, and theories of electromagnetic wave propagation further consolidated the
field of optics.
One of the earliest contributions of optics to biomedical sciences was the introduction of the field of spectroscopy through the observation of the absorbance of
spectral lines from a light source with a continuous spectrum in the year 1862. The
resulting philosophy of blackbody radiation was instrumental in the development of
both spectroscopy and thermography, where the emitted radiation was used to calculate the temperature of a body. Thermography later proved useful to detect inflammatory responses of surgeries, as it is often accompanied by an elevated temperature profile. The scattering of light described by Lord Rayleigh in 1871 based on
earlier observations by John Tyndall was instrumental in describing polarization and
wavelength-dependent scattering, which has huge implications while probing any
biological medium. Rayleigh’s theory of scattering combined with Gustav Mie (for
larger particles) and the quantum concept introduced by Planck in 1900 followed by
the wave-particle duality introduced by Albert Einstein in 1905 constituted the basis
of the modern biomedical optics theories.
As the theory of optics and spectroscopy was being developed, the biomedical
applications of optical techniques were conceived at the end of the nineteenth century,
almost two hundred years after the discovery of the microscope. The discovery of
X-rays by Roentgen in 1895 had wide implications in biomedical imaging. This
was followed by the discovery of Raman scattering in 1928 by C.V. Raman. The
field of biomedical imaging has gained significant momentum over the last three
decades with the introduction of additional imaging techniques such as phase contrast
microscopy, fluorescence spectroscopy and imaging, infrared imaging, near field
optical microscopy, confocal microscopy, optoacoustic imaging, terahertz imaging,
and hyperspectral imaging.
2 Scattering and Absorption
The way light or photons interact with biological matter dictates the principles of
biomedical imaging. These interactions can be broadly classified into absorption
and scattering. In absorption, the molecules absorb the energy of photons and are
excited to their electronic or vibrational energy levels, which may be re-emitted nonradiatively or through fluorescence, phosphorescence, inelastic scattering or accousto
S. P. Singh and S. Siddhanta
by Antoine van Leeuwenhoek. In the 1800 and early 1900, rapid developments
started taking place with the development of ‘ophthalmoscope’ by German scientist
Hermann Ludwig Ferdinand von Helmholtz [1]. This was followed by the invention of the maser (microwave amplification by stimulated emission of radiation) in
1954 which was the predecessor of Laser discovered by Charles Townes and Arthur
Schawlow, although the concept of stimulated emission was introduced by Albert
Einstein in 1917. The advent of the first solid-state laser by Theodore H. Maiman
added a new dimension to the field of optics. The development of important concepts
such as diffraction demonstrated by Thomas Young, polarization by Etienne Louis
Malus, and theories of electromagnetic wave propagation further consolidated the
field of optics.
One of the earliest contributions of optics to biomedical sciences was the introduction of the field of spectroscopy through the observation of the absorbance of
spectral lines from a light source with a continuous spectrum in the year 1862. The
resulting philosophy of blackbody radiation was instrumental in the development of
both spectroscopy and thermography, where the emitted radiation was used to calculate the temperature of a body. Thermography later proved useful to detect inflammatory responses of surgeries, as it is often accompanied by an elevated temperature profile. The scattering of light described by Lord Rayleigh in 1871 based on
earlier observations by John Tyndall was instrumental in describing polarization and
wavelength-dependent scattering, which has huge implications while probing any
biological medium. Rayleigh’s theory of scattering combined with Gustav Mie (for
larger particles) and the quantum concept introduced by Planck in 1900 followed by
the wave-particle duality introduced by Albert Einstein in 1905 constituted the basis
of the modern biomedical optics theories.
As the theory of optics and spectroscopy was being developed, the biomedical
applications of optical techniques were conceived at the end of the nineteenth century,
almost two hundred years after the discovery of the microscope. The discovery of
X-rays by Roentgen in 1895 had wide implications in biomedical imaging. This
was followed by the discovery of Raman scattering in 1928 by C.V. Raman. The
field of biomedical imaging has gained significant momentum over the last three
decades with the introduction of additional imaging techniques such as phase contrast
microscopy, fluorescence spectroscopy and imaging, infrared imaging, near field
optical microscopy, confocal microscopy, optoacoustic imaging, terahertz imaging,
and hyperspectral imaging.
2 Scattering and Absorption
The way light or photons interact with biological matter dictates the principles of
biomedical imaging. These interactions can be broadly classified into absorption
and scattering. In absorption, the molecules absorb the energy of photons and are
excited to their electronic or vibrational energy levels, which may be re-emitted nonradiatively or through fluorescence, phosphorescence, inelastic scattering or accousto