R F I D

Presented by

ROHIT MISHRA

1107731084ECE 3rd year

Under the guidance of

Er . PRATIK DUBEY

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

CONSTRUCTION

The construction of LTS is as shown...

WORKING PRINCIPLE

Laser triangulation sensors determine the position of a target bymeasuring 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 .

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 thustends to dominate the field. Under 'ideal' conditions , PSD sensorsperform to expectation . However, the reliability and repeatabilityof 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 .

PSD systems are also very sensitive to light intensity , and if thischanges 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 .

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

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.

APPLICATION OF LTS

Ride height measurement on the car

Displacement measurement

Thickness measurement

Tyre deflection

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.