Laser displacement sensor (LDS)

http://www.em4sys.com/

Diffused reflection type

• The light source (LD: Laser Diode) and PSD (Position sensitive detectors) are placed in one body. The laser beam is reflected by the surface (pa-per, plastic, metal, etc) that is in mo-tion

http://www.measurecentral.com/technology/semiconductor.php

Direct reflection type

• The light source (LD) and PSD are placed in one body. The laser beam is reflected by the mirror attached to the moving surface

[5]

Measurement Principle

Light spot falls

on the PSD

Light spot falls

on the PSD

Electric charge(Proportional to the light

energy)

Electric charge(Proportional to the light

energy)

Charge is driven and collected

by electrodes

Charge is driven and collected

by electrodes

Photo-currentsby the electrodes

are inversely proportional

to the distance

Photo-currentsby the electrodes

are inversely proportional

to the distance

Photo-currents are processed

using the processing board

We can get the distance from output voltage

Photo-currents are processed

using the processing board

We can get the distance from output voltage

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Our Setup (Total reflection type)

– Head model: TBMPH– Processing board model: ASPB-

TRI– Full scale (FS): ±10 mm – Nominal distance: 32 mm– Resolution: FS/4000(peak-peak)

FS/10000(R.M.S)

– Bandwidth: 100 Hz– Non-linearity: below 0.2 %– Output: ±10 V– Wavelength: 850 nm, 5 mW– Power: AC 220 V/ 60Hz

[7]

Stage Z Movement Measurement

Up and down according to the distance between

sensor and mirrorStage up and down

Optical head