METHOD AND APPARATUS FOR MEASURING
THICKNESS OF FAT USING INFRARED LIGHT
BACKGROUND OF THE INVENTION
The present invention relates to measuring the thick
ness of body fat. More speci?cally, the present inven
tion includes a method and apparatus for non-invasively
determining body fat thickness using infrared light.
In today’s health conscious world, people are becom
ing aware ?tness involves more than maintaining proper
body weight as indicated by a bathroom scale. Muscle
tissue is heavier, and generally more desirable than fat
tissue, but a scale treats their weights the same. It is
necessary to determine the amount of body fat to get an
accurate indication of total ?tness.
Body fat has been measured using many different
techniques. By immersing a body in water, its total fat
composition can be determined. A simpler technique
involves measuring the thickness of fat at various loca
tions on the body using a skinfold caliper. Unfortu
nately, accurate results with a skinfold caliper require
not only consistent operation of the calipers, but also
require a second person to take the measurements in
his therefore a principal object of the present inven
tion to provide a device for noninvasively determining
the thickness of a layer of fat.
It is a principal feature of the present invention to use
infrared light to measure the thickness of fat.
The foregoing and other objectives, features and
advantages of the present invention will be more readily'
understood upon consideration of the following de
tailed description of the invention taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is general block diagram of an illustrative
embodiment of a device for measuring the thickness of
a layer of fat according to the present invention.
FIG. 2 is a bottom view of the sensor of the device of
FIG. 3 is a elevational view of the sensor in contact
with ?esh, taken along line 3-—3 of FIG. 2.
FIG. 4 is a schematic diagram of a circuit for a device
which embodies the present invention.
DETAILED DESCRIPTION OF THE
locations where the person being measured cannot
Referring to the drawings, in FIG. 1 a block diagram
is shown of a meter 10 which embodies the present
readily see the caliper reading if attempting to do the
invention. The meter comprises a power supply 12, two
measurement on him or herself.
infrared emitting diodes (IREDs) 16 and 18, ?ve photo
transistors 20, a summing ampli?er 22, an analog-to
The measurement of fat layer thicknesses is also im~
portant to the meat packaging industry, with the result
that various methods have been used to measure fat on
animals. However, many of the fat measurement tech
niques used in that industry are invasive and thus inap
propriate for ?tness measurement purposes. For exam
ple, Shigeo Tauchi et al. Japanese laid-open patent ap
plication No. 56-160622 describes using colored ?lters
digital (A/D) converter 24, and a display 26. The
IREDs and the photo-transistors constitute a sensor 28
which is enclosed on all sides except its bottom by a
light shield 30. The power supply 12 biases the ?rst
IRED 16 to provide a steady, low-intensity infrared
(IR) light. The timer 14 controls the second IRED 18 to
provide periodic pulses of high intensity IR light.
to optically determine the fat thickness for a butchered
cross section of meat, and Knudsen et al US. Pat. No.
3,671,858 discloses a method of using a needle having
Referring now to FIG. 2, the two IREDs 16 and 18
are positioned adjacent each other and are equidistant
from each of the ?ve photo-transistors 20. The light
electrical contacts to measure electrical resistances be 40 shield 30 surrounds the IREDs and photo-transistors on
tween various layers of flesh.
the four sides and top while allowing their bottom sur
Yoshio Takemori Japanese laid-open application No.
faces to be exposed.
60-181606, Hiroyuki Toyokawa Japanese laid-open ap
The sensor 28 is shown in contact with skin tissue 40
plication No. 62-156508, and Stouffer US. Pat. No.
in FIG. 3. Beneath the skin tissue is a layer of adipose,
4,785,817 each disclose a noninvasive method of mea 45 or fat, tissue 42, beneath which is muscle tissue 44. The
suring fat thickness using ultrasonic waves.
light shield 30 prevents the photo-transistors 20 from
being exposed to ambient light. The ?rst IRED 16
SUMMARY OF THE INVENTION
(FIG. 2) floods the adjacent volume of flesh with low
intensity IR light, establishing a base illumination level
The present invention provides apparatus and means
using infrared radiation for quickly, accurately, and’ and thereby reducing the effect of ambient light on the
noninvasively measuring the thickness of body fat.
measurement. The second IRED 18 emits periodic
pulses of high intensity IR light. The IR light from both
In accordance with the present invention, a pair of
IREDs is refracted by the adipose tissue; its intensity at
infrared emitting diodes, one emitting a steady, low
locations distant from the IREDs being indicative of the
intensity light, and the other emitting periodic, high
intensity pulses of light, are placed against the skin 55 thickness of the layer of fat 42.
Each of the photo-transistors 20 provides a detection
where the fat is to be measured. The low-intensity,
signal representative of the intensity of IR light present
steady illumination provides a base infrared level in the
at its respective location. Referring again to FIG. 1,
fat and reduces the effect of ambient light, while the
high-intensity pulses refract through the fat, providing
these detection signals are combined by the summing
an indication of its thickness. An array of infrared-sensi 60 ampli?er 22, resulting in a composite signal. The A/D
converter 24 converts the composite signal to digital
form and supplies it to the display 26 which provides an
indication of the thickness of the fat layer.
from ambient light. The photo-transistors provide de
It will be appreciated by those of ordinary skill in the
tection signals proportional to the amount of infrared
light detected, which are then summed and ampli?ed, 65 art that other types of infrared detectors, such as photo
diodes, may be used in place of the photo-transistors
forming a composite signal. The amplitude of this com
described above. The larger surface area of the photo
posite signal is indicative of the thickness of the layer of
diodes may have the advantage of being less sensitive to
fat and may be displayed and recorded.
tive photo-transistors are placed against the skin at pre
determined locations near the two diodes, yet shielded