Microscopic Laser Doppler Vibrometer

Transcription

1 Microscopic Laser Doppler Vibrometer

2 System Configuration - 1 PC Controller (APU-Analog processing unit, DPU-Digital processing unit) Optic Head (MEMS Type, XS Type) Function Generator Power Supply Testing Sample

3 System Configuration - 2 Pre-AMP P Q AVID Optical head OUTPUT Displacement Bode Plot FFT RRO&NRRO Mechanical System Post-Amp Swept sine Function Generator Q P High Speed A/D card

4 Optical configuration Microscope type

5 Optical configuration Dual beam type Rotatable Mount LASER FIBER APERTURE MIRROR PBS 1 R/A MIRROR BEAM 1 CCD OBSERVING PORT BEAM 2 4 % NPBS SINGLE / DUAL BEAM CHANGING MECHANISM PBS 3 QW(45) FOCUSING LENS 2 FOCUSING LENS 1 PD 1 PD 4 PBS 2 PBS 4 PD 2 PD 3 R/A MIRROR ( WITH PZT)

6 Mechanical configuration Built in stages

7 Quardrature Signal (90degrees phase difference) Ψ 1 (t) = A sin(2 πυt) I 1 (t) = A 2 sin 2 (2 πυ t) Ψ1(t) = A sin(2 πυt+ф/4) I1(t) = A2sin2 (2 πυ t+ Ф/2)

8 Quardrature Signal (90degrees phase difference) Formula Q/2π = Displacement / λ

9 Circular Polarization Interferometry Polarization Details Net linear polarization vector L rotates 2π for every wavelength of relative movement Quadrature signals P and Q obtained by measuring L thru polarizers placed at θ and θ + 45 o Electronic signals oscillate 2π whenever L rotates π P,Q signals oscillate 2π whenever the two measurement surfaces have π( = λ/ 2) relative movement

10 Specification Laser source Model: Phase 1103P (He-Ne Gas Laser) Wave length: 632.8nm Beam diameter: 0.63mm Beam divergence: 1.3mrad Objective Lens 10X: WD: 33mm, NA: 0.28, Focal Length: 20mm, DOF: 3.5um 50X: WD: 13mm, NA: 0.55, Focal Length: 4mm, DOF: 0.9um Spot diameter 10X: 10um 50X: 5um

11 Specification Band width DPU (Digital processing unit) 20MHz for Doppler signal APU (analog processing unit) 3MHz for Doppler signal Displacement error 0.4% of F.S Max. Velocity detectable DPU (Digital processing unit) 6.3m/s APU (analog processing unit) 0.95m/s Displacement detectable 0.1 nm ~ 0.5 mm Operation modes Absolute Modes

12 Specification ME scopeves Vibration analysis software (Optional) * First Mode *Second Mode *Third Mode

13 Application PZT Actuator PZT vibrator - Displacement: 329.5nm - Frequency: 1790Hz - Velocity: 3.70 mm/s Measurement Data (0.4% error) - Displacement: nm - Frequency: Hz - Velocity: 3.71 mm/s

14 Application Micropump Displacement of a micro-pump (Used by permission of CSIST, Taiwan)

15 Application - Bode plots of pickup head Sweeping frequency : from Hz Sweeping points : 400 pts Sweeping mode : Log Scale First resonant frequency (f 0 ) : 57.8 Hz High resonant frequency (f 0 ) : ~ khz

16 Application - Ultrasonic acoustic surface wave Laser Interferometer trigger signal Q-Switch pulse laser Digitizer Oscilloscope Displacement (nm) Cp Laser interferometer specimen Precision micro-meter conical transducer Translation Stage x-y Voltage (V) NBS conical transducer Time ( ) Ultrasonic wave measurement (Used by permission of NDT lab.,)

17 Application Spindle Motors Spindle Motor Optical head of AVID Optical Table 1000 Total Indicated Runout of An Air-Bearing Spindle Motor Runout (nm) time (m s)