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January 29, 2007Videometrics IX, Electronic Imaging 2007, San Jose, CA, U.S.A. Real-Time Range Imaging by Phase-Stamp Method Using Correlation Image Sensor.

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Presentation on theme: "January 29, 2007Videometrics IX, Electronic Imaging 2007, San Jose, CA, U.S.A. Real-Time Range Imaging by Phase-Stamp Method Using Correlation Image Sensor."— Presentation transcript:

1 January 29, 2007Videometrics IX, Electronic Imaging 2007, San Jose, CA, U.S.A. Real-Time Range Imaging by Phase-Stamp Method Using Correlation Image Sensor Akira Kimachi 1 and Shigeru Ando 2 1 Osaka Electro-Communication University, Japan 2 The University of Tokyo, Japan

2 Active Range Imaging Active range imaging — Image sensor + Active light –Time-of-flight methods –Triangulation methods # of frames (scans) Interpixel image processing Image intensity- dependence Light spotManyNoneYes Light stripeManyStripe detectionYes Time stamp light stripe 1NoneYes Structured light1Fringe detection Fringe order Yes Phase-shifting structured light 3-4 or moreNoneNo

3 Depth Scan angle of sheet beam Stripe image location Light Stripe Range Finder (LSRF)

4 Time Stamp LSRF (TSRF) Frame-rate operation Pixel-wise sensing –One image for one beam scan –Record a “Time Stamp” for light stripe arrival at each pixel “VLSI silicon range finder” –Gruss et al. (1991) –Kang et al. (1994) –Yokoyama et al. (1994) depth beam angle time stamp

5 TSRF threshold LSRF Effect of Spatially Nonuniform Reflectance/Background Intensity-dependent detection of light stripe causes errors in LSRF and TSRF nonuniform surface reflectance nonuniform background illumination nonuniform surface reflectance nonuniform background illumination

6 Objectives Goal — Real-time active range imaging –Frame-rate operation –Pixel-wise sensing (image processing error-free) –Robustness to spatial nonuniformity in Surface reflectance Background illumination Solution — Phase-Stamp Range Finder (PSRF) –Three-Phase Correlation Image Sensor (3PCIS) –Detect the sheet beam angle by “phase stamp”

7 Three-Phase Time-Domain Correlation Image Sensor (3PCIS) temporal correlation S. Ando and A. Kimachi, IEEE Trans. ED (2003) average intensity

8 Phase-Stamp Range Finder (PSRF) Three-phase reference signals : Frame rate : Object surface reflectance : Sheet beam intensity : Background light intensity : Arrival time of light stripe Image intensity at

9 Phase-Stamp Imaging (1) Sheet beam arrives (2) Phase stamped (3) Converted to beam angle one scan one image

10 Real-Time Range Imaging by PSRF 3PCIS output Phase stamp Total light image Sheet beam image Range imageBeam angle image known function by design Frame-rate range imaging Pixel-wise beam angle detection Robust to spatially nonuniform reflectance/background Phase stamp image uncorrelated to

11 3PCIS Output Images in PSRF Sheet beam-only intensity imageTotal light intensity image : Surface reflectance : Sheet beam intensity : Background intensity 0   /2  /2 Phase stamp image

12 Experimental PSRF System 3PCIS camera –200x200 pixels –Frame fps Sheet beam –7 mW laser diode –Cylindrical lens –Scanning scans/s Reference signals –PC + D/A board Hz Camera and geometry calibration –Based on Zhang’s method Reference signals Sheet beam angle

13 Real-Time 3D Video Capture Phase stampTotal light intensity Sheet beam intensity

14 3D Imaging Examples left thumb & palm cone-shaped surface 23 mm 17 mm 40 mm

15 3D Measurement Accuracy Flat mm from the camera phase stamptotal lightsheet beam PhaseStd. dev.4.08 deg Depth Std. dev.2.35 mm Syst. error-1.96 mm 0   /2  /2 3D surface plot

16 Nonuniform Background Illumination Backgroundabsentstriped Std. dev. [mm] Syst. err. [mm] phase stamptotal lightsheet beam

17 Nonuniform Surface Reflectance Reflectanceuniformstriped Std. dev. [mm] Syst. err. [mm] phase stamptotal lightsheet beam

18 Conclusions Phase-stamp range finder using the 3PCIS –Frame-rate operation –Pixel-wise sensing –Robustness to spatial nonuniformity in Surface reflectance Background illumination Evaluation by an experimental system –Real-time range fps –Accuracy Deviation — 2.35 mm → fixed pattern noise (~4 deg) removal Systematic error — mm → geometry calibration

19 Outline Introduction –Real-time active range imaging Phase-stamp range finder (PSRF) –Three-phase correlation image sensor (3PCIS) –Phase-stamp imaging Experimental system Results Conclusion

20 Previous Results Other real-time range finders using 3PCIS –Phase-modulated sheet beam Kimachi et al., Trans. IEE Japan (2001) –Phase-modulated structured light Goto et al., 19th Sensor Symposium (2002) Ono et al., 21st Sensor Symposium (2004) PSRF is simpler –No modulated light needed


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