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Biologically Inspired Robotics
have a uniform concentration, the fluid concentration and absorption rate
are not constant.
Arterial blood flow is periodical. Therefore, there are changes in pressure,
which are responsible for changes in the shape of the arteries. This variation
of shape changes the light path. Similar to venous blood, the presence of
blood flow means that the concentration and absorption rate are variable.
If S tissue , S vein , and S artery are constant, variation of absorbance is expressed
as formula (10.5):
ΔAbs = ε artery C artery Δd artery + K
(10.5)
ΔAbs is variation of absorbance. <Δd artery > is variation of the average length
of the path followed by the light in the artery. K is the constant including the
effect of tissues, veins, and scattering.
Therefore, it is safe to assume that variation of light detected by the light
receiver is a direct result of the variation in blood flow and concentration.
10.3 Device Development
10.3.1 Hybrid Sensor Probe
The objective is to develop a sensor that can capture both optical and bioelectrical data simultaneously by using a single sensor probe. A hybrid sensor
probe consists of the following components.
• Optical elements
• Electrode
• Amplifier
Optical elements include a light emitter, a light receiver, and a light-guiding transparent acrylic bar. Holography laser modules were used as light
sources for the optical sensors. The laser module has a laser diode and
photodiodes and is able to keep the size of the sensor small. Common
near-infrared imaging devices usually collect the light using optical fibers
and the optical signals are converted into electric signals on the external control board. The hybrid sensor probe converts optical signals into
electrical signals. Therefore, an optical fiber is not necessary, and handling of the hybrid sensor probe is easy. The light is emitted to the scalp
through the light-guiding bar. The light-guiding bar is also used to push
hair aside.
Biologically Inspired Robotics
have a uniform concentration, the fluid concentration and absorption rate
are not constant.
Arterial blood flow is periodical. Therefore, there are changes in pressure,
which are responsible for changes in the shape of the arteries. This variation
of shape changes the light path. Similar to venous blood, the presence of
blood flow means that the concentration and absorption rate are variable.
If S tissue , S vein , and S artery are constant, variation of absorbance is expressed
as formula (10.5):
ΔAbs = ε artery C artery Δd artery + K
(10.5)
ΔAbs is variation of absorbance. <Δd artery > is variation of the average length
of the path followed by the light in the artery. K is the constant including the
effect of tissues, veins, and scattering.
Therefore, it is safe to assume that variation of light detected by the light
receiver is a direct result of the variation in blood flow and concentration.
10.3 Device Development
10.3.1 Hybrid Sensor Probe
The objective is to develop a sensor that can capture both optical and bioelectrical data simultaneously by using a single sensor probe. A hybrid sensor
probe consists of the following components.
• Optical elements
• Electrode
• Amplifier
Optical elements include a light emitter, a light receiver, and a light-guiding transparent acrylic bar. Holography laser modules were used as light
sources for the optical sensors. The laser module has a laser diode and
photodiodes and is able to keep the size of the sensor small. Common
near-infrared imaging devices usually collect the light using optical fibers
and the optical signals are converted into electric signals on the external control board. The hybrid sensor probe converts optical signals into
electrical signals. Therefore, an optical fiber is not necessary, and handling of the hybrid sensor probe is easy. The light is emitted to the scalp
through the light-guiding bar. The light-guiding bar is also used to push
hair aside.