Feature Article 10 dynamically moving specimen. On the other hand, hand, other the On holography specimen. of moving measurement the for dynamically useless or are they process specimen, of sequential need (3-D) information three-dimensional measure to scanning techniques techniques. these imaging Since noninvasive as the coherence specimens measure to living used optical usually an are on so mens. and tomography microscopy, speci ng force livi atomic for an microscopy, valuable confocal a microscopy, optical is Conventional image rement Furthermore, cells. measu and tissues bodies, of living function and structure of measurement for necessary are means noninvasive Also, medicine. to them applying and technologies two the combining by life human future in happiness and welfare achieve to important It is on. so and pharmacy, science, life in invent materials, to and functional new phenomenon Biotechnology new discover to us information. enables been large-capacity have process to biotechnology us enables electronics Advanced and advanced. drastically electronics Recently Introduction of cells. measurement image of three-dimensional capabile is technique this using microscopy the that confirmed also was It experiment. preliminary a by confirmed was technique the of holography. validity array. The device digital phase-shifting a by in implemented is wave multiplexing reference space-division The the of multiplexing space-division using phase-shifting simultaneously out carries and interferometry holography digital parallel as called been has technique The objects. moving formeasurement image three-dimensional of capable technique a developed and inventedauthor The Yasuhiro Awatsuji — Parallel Digital Holography Feature Article holography is useless for 3-D image measurement for for measurement image conventional 3-D for useless process, is the of holography Because photographs. of process development the as way same the in fixed and developed, chemically 3-D is plate, ns photographic ai resolution cont which plate, a high- holographic plate. holographic The the records mage, i raphy nge i r on holog beams f laser by two generated of object, an information ference Conventional nter i object. an of Three-Dimensional ImageMeasurement Technique for Moving Cells English Edition No.14 February 2011 English Edition No.14February [1] can instantaneously record 3-D information information 3-D record instantaneously can measurement of dynamically moving objects. moving of dynamically measurement moving object. In recent years, digital holography digital years, recent object. In moving holography digital parallel invented author the Then, object. moving a of measuring incapable is but measurement, 3-D precise and capable of accurate indeed is technique The changed. sequentially are wave reference the of phases the which of holograms several requires technique holography.The an of image digital the in-line the by image only reconstructed the from object extracting of capable technique Holography Holography problem, phase-shifting digital holography was was holography digital invented phase-shifting the solve To problem, decrease. measurement of precision and accuracy the Therefore, object. an of image the is which are wave, which desired the on image, superimposed are waves, unwanted conjugate the and wave diffraction non- problem that a such serious holography has digital in-line However, holography. digital of implementation fine interference fringe using an image sensor, in-line in-line sensor, holography image digital an using fringe interference Torecord fine fringe. interference fine resolve to small too however, is, sensor pixel image pitch of The an computer. a using object an of image 3-D reconstructs numerically and sensor, image an using image image fringe interference 3-D the for records technique This technique objects. a moving of as measurement studied actively been [5] . The phase-shifting digital holography is a is holography digital phase-shifting The . [1] [6-8] was invented as a technique for recording recording for technique a as invented was capable of accurate and precise 3-D 3-D precise and accurate of capable [3] has been frequently adopted for for adopted frequently been has [2-4] — has has Technical Reports
Mirror Feature Article LASER Half mirror LASER Mirror
Lens Lens Lens Mirror Illumination Reconstructed Reference Mirror wave Parallel Digital Holography wave wave — Three-Dimensional Image Measurement Technique for Moving Cells —
Yasuhiro Awatsuji Reconstructed Observer Object Object wave Holographic image Hologram plate (Virtual image)
The author invented and developed a technique capable of three-dimensional image measurement for (a) (b) moving objects. The technique has been called as parallel digital holography and carries out phase-shifting interferometry simultaneously using space-division multiplexing of the reference wave in digital holography. Figure 1 Schematics of holography. The space-division multiplexing is implemented by a phase-shifting device array. The validity of the technique (a) Recording, (b) reconstuction. was confirmed by a preliminary experiment. It was also confirmed that the microscopy using this technique is and reconstructing 3-D image of an object. When light The other beam does not contain the information of the capabile of three-dimensional image measurement of cells. wave irradiates an object, the light wave is scattered from object and is called as the reference wave. The two waves each point of the object. Then, the amplitude and phase irradiate the holographic plate, and then generate an of the light wave are modulated by the object, and the interference fringe image on the plate. The medium that wavefront containing 3-D information of the object is records the interference fringe image of an object is called generated. To record the wavefront, both amplitude and hologram in general. After chemical development process phase are needed to be recorded. However, a holographic of the plate, the plate is illuminated by the same laser plate and an image sensor can record only the light wave’s beam as the reference wave, then the reconstructed image intensity, which is the same as the amplitude. To record appears at the same position where the object was. the phase, the phase information is converted into intensity information by using the reference wave and is Digital Holography recorded as form of interference fringe image. Figure 1 shows the schematic diagrams of the recording and Figure 2 shows a schematic diagram of the concept of reconstruction of hologram. A laser beam is divided into digital holography[2-4]. This technique records the two beams. One beam irradiates the object and is interference fringe image using an image sensor such as scattered. The scattered wave is called as the object wave. CCD and CMOS, and numerically reconstructs 3-D
Recording Half mirror Object wave Mirror Lens LASER Object
Image Reconstruction Reference Beam sensor wave combiner
Mirror Mirror Lens
Figure 2 Schematic of digital holography.
English Edition No.14 February 2011 11 Feature Article 12 shifting technique has been applied been has technique shifting interference of phase- object, To an image the only fringes. obtain fine record to large too are sensors of image pitch pixel and size pixel the because is the of This image object. the on superimposed are wave diffraction non- the and image conjugate the is both because allows image inaccurate single reconstructed the a holography measurement, from digital instantaneous this object an Although of image hologram. the reconstructs author proposed a parallel digital holography. digital aparallel proposed author for the measurement, useless instantaneous is perform can that it method object, phase-shifting a To the achieve measurement. of instantaneous image true achieves method phase-shifting the Although mirror. transducer shifts. phase wave by ora piezoelectric- using plates changed sequentially is wave different reference the of phase with the Usually, waves reference using recorded sequentially holograms two than more requires Parallel digital holography digital Parallel Parallel Digital Holography Fresnel transform A sensor. image an by fringe interference record to as so fringe of interference interval the enlarge to sensor image digital this In an irradiates wave orthogonally reference holography,the holography. digital of implementation for adopted frequently been has holography digital In-line plate. holographic uses that holography conventional the to comparison in limited not is beam of laser wavelength available process; focusing mechanical a without acquired instantaneously be can depth desired at of objects 3-D images focused and objects; of images 3-D for easy is evaluation quantitative required; not is media recording developing for process a chemical features: following the attractive has technique acomputer. The using image fringe interference the from propagation wave light the calculating by ofobject image Feature Article The in-line digital holography using the Fresnel Fresnel the using holography transform digital in-line image. the The reconstruct to sensor image the on recorded example shows the case that the number of the phase phase the of This number four. is shifts the that algorithm. case digital the shows example parallel reconstruction of the and holography implementation the of example a from wave hologram. single object the only of distributions phase and wave of in the conventional in-line digital holography. holography. digital in-line reference the conventional in the in placed of is wave array device phase-shifting holography. digital in shown As parallel English Edition No.14 February 2011 English Edition No.14February [3] alone is the simplest implementation and and implementation simplest the is alone Figure 3(a) Figure [3] Figure 3 Figure is generally applied to the hologram hologram the to applied generally is [6-8]
schematically illustrates an an illustrates schematically shows the principle of the the of principle the shows Parallel Digital Holography can reconstruct amplitude amplitude reconstruct can [5] . The technique technique The . Fig.3(b) , a , sensor, respectively.sensor, image the to object the from distance the and beam, laser Here, i Here, U(X, Y) can be calculated by applying the same same the digital follows.phase-shifting as applying holograms four the holography to by conventional the in calculated calculation be wave can object Y) the of U(X, amplitude complex The obtained. I holograms, four shifts, phase four the for interpolation and relocation this out carrying being pixel adjacent the values. By using interpolated are image before 2-D the in relocated not located pixels of values were The they extracted. which at same the at image 2-D addresses another in relocated are pixels extracted the shift, phase each For the from hologram. recorded extracted are shift pixels phase The same the technique. containing proposed the of reconstruction 1(c) Figure obtained. A laser operating at 633 nm, serving as the the as serving nm, 633 at operating laser A be to obtained. hologram the produce equivalently to plate wave of ahalf-wave aquarter- holography plateand consisting digital phase-shifting conventional in employed system optical an used author the available, commercially not is device array phase-shifting a the Since verify technique. to proposed conducted was experiment preliminary A Preliminary Experiment the image sensor by using polarization technique polarization by using sensor image the on attached be can device array For phase-shifting example, holography. digital parallel implement to are possible configurations Other distributions. a phase four-step captures sensor image the wave reference the the containing with recorded hologram Thus, pixel. the of that as same the is sensor image the on cell imaged ofthe size The sensor. image the in pixels of arrangement the the with corresponds of plane sensor image distribution the on wave an phase by reference the that sensor so image system the onto imaging imaged is The device thickness. array four-step periodical a with plate a using glass implemented be can device array The shifting. phase the for required 3π/2, π, π/2, 0, four-step distributions, phase periodical the generates which 2×2-cell a with configuration array segmented a is device array The U(X,Y) =∫ , λ and Z are the imaginary unit, the wavelength of wavelength the unit, imaginary the are Z and exp -∞ ∞
∫ ⎦――⎤ -∞
∞
shows the processing procedure for for procedure processing the shows 2πi ⎠――⎞
λ {I(0)-(π)}+i/2)-(3/2)}
⎠ ⎞ ⎬ ― ― Z+ (X-x) 2Z 2 +(Y-y) 4 (0), (0),
2 I
⎛ ⎨ ⎝ (π/2), ― ―
⎣――⎡ ⎝――⎛ dxdy. I (π), (π), … I ……… (3π/2), are (3π/2),are [7] . (1) Technical Reports
Feature Article Parallel Digital Holography
Phase-shifting array device Phase Image distribution sensor Hologram 1pixel
Reference wave−>
(a)
Beam splitter Object
Mirror
LASER Imaging system Image sensor
Phase-shifting array device Beam combiner (b)
Hologram Reconstructed image
Sampling Calculation of Interpolation light propagation
Phase-shifting interferometry
Complex amplitude
(c)
Figure 3 Schematics of the parallel digital holography. (a) Principle, (b) an example of optical implementation of parallel digital holography, (c) algorithm for reconstructing the image of object.
light source, and a CCD camera with 768(H)×493(V) For the hologram recorded using each phase-retardation, pixels of pixel size 11 μm (H)×13 μm (V) were used. Four the pixels corresponding to the same phase retardation by holograms, I(ø) (ø= 0, π/2, π, 3π/2), were optically the phase-shifting device were extracted at 1-pixel obtained in sequence using the half-wave plate and intervals. The extracted pixels for the four holograms quarter-wave plate. Here, ø represents the phase shift of were relocated in a single 2-D image at the same the reference wave. addresses at which they were located before being
English Edition No.14 February 2011 13 Feature Article 14 and and W he n a wat e r-f le a wa s u se d a s a n obje c t , t he he t , t c are obje n in shown holography a digital s a parallel the d and se technique u alone s transform wa Fresnel the by a obtained le images r-f reconstructed e wat a n he W in shown holography are digital parallel the and alone transform Fresnel using holography digital in-line single-shot conventional the by images reconstructed The the generated. using equivalently was device array recorded be to hologram the Thus extracted. Feature Article Figure 5 Figure 4 Figure (b) English Edition No.14 February 2011 English Edition No.14February . Cells of onion skin were chosen as an object. object. an as chosen were skin onion of Cells . Figs. 5(a)Figs. (a) Fresnel transform alone technique, (b) parallel digital holography. Each image consists of 512 of ×512 pixels. consists image Each holography. digital (b) parallel technique, alone transform (a) Fresnel 512 of ×512 pixels. consists image Each holography. digital (b) parallel technique, alone transform (a) Fresnel flea. awater was object The experiment. preliminary the in images Reconstructed peer. onion of cells were objects The experiment. preliminary the in images Reconstructed (a) (a) 300µm 100µm and and
(b) Parallel Digital Holography , respectively. Internal Internal respectively. , Figs. 4(a)Figs.
(b) (b) more accurately than the Fresnel transform alone alone transform Fresnel the technique. than accurately more much object the reconstructs holography digital parallel from only seen Fig. 5(b) clearly been has object the of structure . Both experimental results show that the the that show results experimental Both . Technical Reports
Feature Article Parallel Digital Holography Conclusion
Parallel digital holography has been introduced as a technique capable of noiseless instantaneous measurement of 3-D objects. The results of a preliminary experiment have shown the validity of the proposed technique. The technique will contribute to the measurement of dynamically moving 3-D objects, such as those of interest in biology, structure of a living cell, spatial distribution of cells, flow inside a cell.
Reference
[1] D. Gabor, “A new microscopic principle,” Nature (London) 161, 777-778 (1948). [2] J. W. Goodman and R. W. Lawrence, “Digital image formation from electronically detected holograms,” Appl. Phys. Lett. 11, 77-79 (1967). [3] U. Schnars and W. Jueptner: Digital Holography, Springer (2005). [4] T. –C. Poon, “Recent progress in optical scanning holography” J. Holography Speckle 1, 6-25 (2004). [5] I. Yamaguchi and T. Zhang, “Phase-shifting digital holography,” Opt. Lett. 22, 1268-1270 (1997). [6] M. Sasada, Y. Awatsuji, and T. Kubota, “Parallel quasi-phase-shifting digital holography that can achieve instantaneous measurement,” in Technical Digest of the 2004 ICO International Conference: Optics and Photonics in Technology Frontier 187-188 (International Commission for Optics, 2004). [7] M. Sasada, A. Fujii, Y. Awatsuji, and T. Kubota, “Parallel quasi-phase-shifting digital holography implemented by simple optical set up and effective use of image-sensor pixels,” in Technical Digest of the 2004 ICO International Conference: Optics and Photonics in Technology Frontier (International Commission for Optics, 2004), 357-358. [8] Y. Awatsuji, M. Sasada, and T. Kubota, “Parallel quasi-phase-shifting digital holography,” Appl. Phys. Lett. 85 1069-1071 (2004).
Yasuhiro Awatsuji Division of Electronics Graduate School of Science and Technology Kyoto Institute of Technology
English Edition No.14 February 2011 15