This document discusses various photo optical techniques used to capture and analyze human movement, including cinematography, video, and optoelectric techniques. It describes cine cameras, their characteristics, types, lenses, and camera positioning. It also discusses other measurement devices like accelerometers, gyroscopes, force platforms, footswitches, and instrumented walkways that are used along with video recordings to measure temporal gait parameters and forces during walking. The analysis of gait cycle and advantages of using video recording for gait analysis are also summarized.

1. PRESENTED BY :-
PRABHAT KUMAR
ARYA
PIYUSH BHARDWAJ
HEMANT AGGARWAL

2.  THE chinease saying “A PICTURE IS WORTH MORE
THAN TEN THOUSAND WORDS” gives a very
important message to biomechanics
 The imaging measurement techniques give
description of human movement in a very purposeful
manner i.e. presentation of the position or of the body
part in space & time.

3. INTRODUCTION
 Photo optical devices, are the devices which are utilize
to capture movement of body from images sensors to
triangulate the 3D position of subjects between 2 or
cameras calibrated to provide overlaping projections.

4. THERE ARE 4 TECHNIQUES
Cinematography
Video
Optoelectric techniques

5. Cinematography
 cine cameras
these are available in 8mm, super 8 ,16 mm ,35 mm &
70mm
 8mm, super 8 are least expensive but the image size is
small & also these have become obsolete(out-dated)
 35 mm & 70mm cameras offer a large images size but
are expensive
 16 mm cameras are used for biomechanical research
purpose as these a compromise between the cost & the
images size

6. CHARACTERISTICS OF A CINE CAMERA
 It must have stabilized frequency.
It must provide a range of frequency between 64-200
frames per second .The preferable upper limit is 500 f.P.S.
 It should provide time information on the film itself.
It should synchronize with another cameras or the other
measurement devices eg. dynamometric platform or
electrogoniormerters

7. Types of cine cameras
 The are three type of cine cameras
Intermittent pin-registered
Rotating prism
Streak cameras.

8.  The type of mechanical
movement puts constraints of
the maximum possible speed
of these cameras.
 Operate up to 500 frames per
sec.
 Advantage of these camera is
that these produce extremely
high resolutions.

9. • Rotating prism cameras provide a frequency up to 2500
fps with a short exposure time.
• The disadvantage of these cameras is the poor
resolution than the intermittent cameras

10.  These are used to study the self-luminous events in the
linear motion.
 These cameras operates in the range of 20,000 picture
per se. to 1 million pictures per sec.
For evaluation of technique, usually pin registered
cameras are used as these give good resolution as well as
the range of camera speed is sufficient for most of the
events

11. LENS
 The choice of the lens depends upon the purpose & the
filming situations but there are certain other factors:-
Distance from the object: usually the distance between
the object & camera is kept large to keep the distortion or
the perspective error to the minimum.thus, preference goes
towards a tele lens.
 Recording area : usually zoom lenses are used as with
zoom lens desired area can be obtained by keeping the
camera & the object distance large

12. Camera position
 For biomechanical evaluation, camera should be
placed perpendicular to the plane of motion of the
object.
 In case it is not possible to position the camera
perpendicular to the plane of motion then a necessary
correction should be made using trigonometric rules.

13. Accelerometers
 Accelerometers, measure acceleration.
 The type of accelerometer used in gait analysis is
usually very small, weighing only a few grams.
 It normally only measures acceleration in one
direction, but more than one may be grouped together
for two- or three-dimensional measurements.
 Typically, accelerometers have been used for gait
analysis in one of two ways:
 1. either to measure transient events
 2.to measure the motion of the limbs.

14. GYROSCOPES
 A gyroscope is a device used for measuring or
maintaining orientation and angular velocity

15. FORCE PLATFORMS
 The force platform, which is also known as a
‘forceplate’, is used to measure the ground reaction
force as a subject walks across it .
 a ‘typical’ design being about 100 mm high, with a flat
rectangular upper surface measuring 400mm by 600
mm
 Within the platform, a number of transducers are used
to measure tiny displacements of the upper surface, in
all three axes, when force is applied to it.


16. Cont…
 a force platform should be mounted below floor level,
the upper surface being flush with the floor.
 If this is not possible, it is usual to build a slightly
raised walkway, to accommodate the thickness of the
platform.

17. Uses in gait analysis:
 Methods of gait analysis-
1. visual gait analysis:- Simplest form of gait analysis
made by unaided human eyes
2.using video recording :- high technology gait
analysis photo optical devices

18. Advantages:
 It helps to overcome two of the limitations of
visual gait analysis:
 the lack of a permanent record
 the difficulty of observing high-speed events.
1. It reduces the number of walks a subject needs to
do during gait analysis
2. It makes it possible to show the subject exactly
how they are walking gait analysis
3. It makes it easier to teach visual gait analysis to
someone else.

19. Analysis of gait cycle through
photo optical devies
 A number of systems have been described which
perform the automatic measurement of the timing of
the gait cycle, sometimes called the temporal gait
parameters.
 Such systems may be divided into two main classes:
1.footswitches
2. instrumented walkways

20. Fooswitches:
 Footswitches are used to record the timing of gait
 If one switch is fixed beneath the heel
 and one beneath the forefoot,
 it is possible to measure the timing of initial contact, foot
flat, heel rise and toe off, and the duration of the stance
phase
 If switches are mounted on both feet, the single and double
support times can also be measured
 The footswitches are usually connected through a trailing
wire to a computer, although alternatively either a radio
transmitter or a portable recording device may be used to
collect the data and transfer them to the measuring
equipment.

21. Instrumented walkways
 used to measure the timing of foot contact, the
position of the foot on the ground, or both
 A conductive walkway is a gait analysis walkway which
is covered with an electrically conductive substance,
such as sheet metal, metal mesh or conductive rubber
 The speed needs to be determined independently,
typically by having the body of the subject interrupt
the beams of two photoelectric cells, one at each end
of the walkway, again connected to the computer

22. Cont…
 An alternative arrangement is to have the walkway
itself contain a large number of switch contacts, which
detect the position of the foot, as well as the timing of
heel contact and toe off.
 This has the advantage that no trailing wires are
required and the walkway can be used to measure both
step lengths and the stride length.