1. ICOSN2001 Yokohama, Japan 1 Measurement of density distribution in a small cell by digital phase-shift holographic interferometry Toshiharu Mizukaki*, Takeshi Seto**, Kazuyoshi Takayama* * Tohoku University, Sendai, Japan ** Seiko-Epson Corporation, Japan (presented by Harald Kleine *)

2. ICOSN2001 Yokohama, Japan 2 Objectives Ordinary sensors require finite volume in the area of interest.  optical diagnostics  no seeding !  appropriate density-sensitive visualization technique Development of a non-intrusive measurement system for the evaluation of fluid flow in micro-machines

3. ICOSN2001 Yokohama, Japan 3 Objectives determine density changes in liquid –in a small cylinder (dimensions: order of millimeters) –under high-frequency oscillation –with high precision (within a few percent)  interferometry

4. ICOSN2001 Yokohama, Japan 4 Experimental Approach Cylindrical test section: Light rays are distorted. Compensation of distortion  adequately shaped outer surface of the cylinder  cylinder material: plexiglass  optical method: holographic interferometry

5. ICOSN2001 Yokohama, Japan 5 Experimental Approach Reference beam interferometry: Sensitivity of the apparatus is limited and fixed. In plane flows: : wavelength K: Gladstone-Dale constant L: depth of test section Increased accuracy of interpolation between fringes  multiple reference beams

6. ICOSN2001 Yokohama, Japan 6 Experimental Approach Measurement method Digital phase-shift holographic interferometry (DPSHI) - two reference beam interferometry - digital data acquisition and image processing - accuracy/resolution of the order of 1/100 fringe Test section design - cylinder with aspheric-lens-type outer surface

7. ICOSN2001 Yokohama, Japan 7 Design of the test section rays have to be parallel after passing the test section n tube n cel n env

8. ICOSN2001 Yokohama, Japan 8 DPSHI – recording system Laser: Ruby laser (694.3 nm, 2J/pulse, 30 ns pulse width) Recording material: Holographic film (ILFORD HOTEC-R, 7000 lines/mm) Method: Double exposure Fresnel hologram (with diffuse object beam, two reference beams)

9. ICOSN2001 Yokohama, Japan 9 DPSHI – reconstruction system Optics: Michelson interferometer (with PZT mounted mirror, tilted mirror and two reconstruction beams) Laser: He-Ne laser (632.8 nm, 35 mW, cw) Image capturing device: CCD camera (480 pixels by 640 pixels)

10. ICOSN2001 Yokohama, Japan 10 Phase demodulation +α +α +α I 0 I 1 I 2 I 3 I 4 φ-3/2α φ-1/2α φ+1/2α φ+3/2α φ i,j (unknown) φ i,j (calculated) recorded intensity (I 1,I 2,I 3,I 4 ) By shifting a mirror with PZT i j φ(x,y) φ : target phase α : added phase by PZT ψ : fringe phase Ｉ : image intensity γ: contrast function

11. ICOSN2001 Yokohama, Japan 11 Measurement system

12. ICOSN2001 Yokohama, Japan 12 Conditions Cylinder dimensions:  7.8 mm x 37 mm Liquid: distilled water Oscillation frequency: 20 kHz with 17  m amplitude Observation trigger: Maximum wall pressure, minimum wall pressure

13. ICOSN2001 Yokohama, Japan 13 Experimental results Min. Max. Wall-pressure profilePhase map Density change along A-B

14. ICOSN2001 Yokohama, Japan 14 Conclusions Digital phase shift holographic interferometry can non-intrusively measure small density changes –at high frequency –in liquid –in confined test sections