Toshiharu Mizukaki*, Takeshi Seto**, Kazuyoshi Takayama* * Tohoku University, Sendai, 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 *) 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 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 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 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 ICOSN2001 Yokohama, Japan

6. Experimental Approach • Measurement methodDigital 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 ICOSN2001 Yokohama, Japan

7. Design of the test section • rays have to be parallel after passing the test section ncel ntube nenv 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) 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) ICOSN2001 Yokohama, Japan

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

11. Measurement system ICOSN2001 Yokohama, Japan

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

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