Laser triangulation sensors use a laser diode to project a light spot onto a target surface. The reflection is focused onto a light detector, and the position of the reflected spot indicates the target's position. There are two main types of receivers - position sensitive devices and charge coupled devices. Position sensitive devices have been used for longer but are sensitive to surface conditions, while charge coupled devices can now react faster with new technology. Laser triangulation sensors offer non-contact measurement with high accuracy, but the laser beam can be a hazard and measurements cannot be made very close to the sensor. They are used for applications like ride height measurement, displacement measurement, and thickness measurement.

1. Presented by
ROHIT MISHRA
1107731084
ECE 3rd year
Under the guidance of
Er . PRATIK DUBEY

2. Laser triangulation sensors can also be used on highly
reflective or mirror surfaces , commonly referred to as
specular . With these surfaces the typical triangulation
sensor , can't be used because the laser light would bounce
directly back into itself . For these cases it is necessary to
direct the beam to the target at an angle . The beam will
reflect from the target at an equal but opposite angle and
focus onto the detector . MTII manufactures laser heads
specifically designed for specular surfaces or any of our
lasers can be mounted at an angle and operated in the
"specular mode" if necessary .
INTRODUCTION

3. CONSTRUCTION
The construction of LTS is as shown...

4. WORKING PRINCIPLE
Laser triangulation sensors determine the position of a target by
measuring reflected from the target surface . A 'transmitter'
(laser diode) projects a spot of light to the target , and its
reflection is focused via an optical lens on a light sensitive
device or 'receiver‘. If the target changes its position from the
reference point the position of the reflected spot of light on the
detector changes as well . The signal conditioning electronics of
the laser detects the spot position on the receiving element and
, following linearization and additional digital or analogue signal
conditioning , provides an output signal proportional to target
position .

6. The most critical element in this arrangement is the receiver ,
which can take one of two forms :
A position sensitive device (PSD) or charge coupled device (CCD).
PSD triangulation has been around for about 25 years and thus
tends to dominate the field. Under 'ideal' conditions , PSD sensors
perform to expectation . However, the reliability and repeatability
of the PSD receiver is compromised by a number of 'real world'
variations in the nature of the target.
Should surface conditions , target texture or tilt change , for
example , this will change the shape of the light spot , altering the
centre of light distribution , and inducing a change in output of
the PSD element , even though the true 'Z' position of the target
has not changed .

7. PSD systems are also very sensitive to light intensity , and if this
changes while the spot position remains the same , it will result
in an output change - the same net effect of a change in target
colour .
CCD lasers first surfaced in Europe around ten years ago , and
helped overcome many of the limitations of PSD technology.
However , the speed of response of the laser to changing surface
conditions was still limited by the controlling microprocessor . If
surface conditions changed rapidly , the device simply couldn't
react fast enough , resulting in a measurement error . But
technology moves on . Today , the latest CCD elements and DSP
devices have virtually eliminated these early shortcomings of the
CCD based receiver .

9. ADVANTAGE OF LTS
 Since it is non contact there is no friction and wear
 Unlimited number of operating cycles since it is not contact
 Can measure distance to small targets since spot size of laser beam
is very small
 High accuracy
 High Resolution
 High speed
 Good reliability
 Good linearity
 Long measurement ranges

10. DISADVANTAGE OF LTS
 No measurement zone of few mm infront of the sensor .
As the measurement range increases this also increases.
 Could be affected if the target surface is irregular
 Laser beam can be hazardous.

11. APPLICATION OF LTS
 Ride height measurement on the car
 Displacement measurement
 Thickness measurement
 Tyre deflection

12. HOW TO REMOVE THE DISADVANTAGE
 The disadvantage of CMMs though , is that it requires contact
with the object being ... Principle of a laser triangulation
sensor. ..... The solution is called segmentation , a manual or
automatic procedure that can remove the unwanted
structures ...
 laser triangulation sensors can be divided into two categories
based upon ... Their operatin principle, advantages/disadvantages
and how to successfully apply them. .... with filtering will
remove some unwanted higher frequency fluctuations.