Kazunori Shinoda

Three-dimensional microscopy by optical scanning holography

We first briefly review a new 3-D imaging technique called optical scanning holography (OSH). We then discuss the techniques 3-D holographic magnification in the context of optical scanning and digital reconstruction. Finally, we demonstrate the 3-D imaging capability of OSH by holographically recording two planar objects at different depths and reconstructing the hologram digitally.

Optical scanning holography

This paper provides a tutorial on the principles of holography, followed by a review of a newly developed 3-D imaging technique in which 3-D optical information of an object cam be extracted by a 2-D optical scan of the object. The technique is called optical scanning holography (OSH). In the context of optical scanning holography, we discuss some of its potential applications such as holographic information transmission and television (TV) system, 3-D image coding and decoding, 3-D microscopy, and 3-D optical remote sensing. In most cases, feasibility has been proven but awaits broader application.

Effective suppression of beam divergence for a high-power laser diode bar by an external-cavity technique.

We describe effective suppression of beam divergence for a high-power laser diode bar by use of an external-cavity technique. Nineteen off-axis external-cavity laser diodes of the high-power laser diode are formed by feedback with a stripe mirror. At three times the threshold current, the diverging angle (1/e2) of the external-cavity laser diode bar is reduced to 1.5 degrees from 6.6 degrees (free running) with 14.1-W peak output power and 70.4% of the radiated power of the free-running state without the external cavity. This technique effectively improves the beam quality of the high-power laser diode bar.

Beam-shaping technique for improving the beam quality of a high-power laser-diode stack.

We report a beam-shaping technique that reconfigures the beams to improve the beam quality and enhance the power density for a ten-array high-power laser-diode stack by using two optical rectangular cubes and two stripe-mirror plates. The reshaped beam has threefold improvement in beam quality, and its power density is effectively enhanced. On the basis of this technique, we focus the beam of the high-power laser-diode stack to effectively end pump a high-power fiber laser.

Twin-image elimination in optical scanning holography

We propose a novel multiplexing technique to solve the twin image problem in optical scanning holography without the use of a spatial carrier, as commonly used in conventional off-axis holography. The technique involves simultaneously acquiring sine and cosine Fresnel zone-lens plate coded images by optical scanning. A complex addition of the two coded images will then be performed and decoded to give a twin-image rejection reconstruction. Computer simulations will be presented to demonstrate the validity of the idea.

Real-Time Optical Holography Using a Spatial Light Modulator

A real-time technique for recording and reconstructing optical holograms is proposed. Holographic recording is accomplished by scanning an object with two superposed light beams of different temporal frequencies. For reconstruction, the scanned information is transferred to an electron beam addressed spatial light modulator for coherent processing and optically read out to reconstruct an image of the scanned object.

Enhancement of emitting power density with a beam-shaping technique for a high-power laser-diode array stack

We present a beam-shaping technique to enhance emitting power density for a high-power laser-diode array stack. By use of a stripe mirror and a high-reflection mirror, the laser source height of 42 mm is folded to 21 mm and the emitting power density is increased to 365 W/cm 2 from a raw emitting power density of 194 W/cm 2 . Moreover, the beam parameter product (BPP) that is used to evaluate the beam quality is effectively improved to 168-mm mrad from a raw BPP of 336-mm mrad in the fast axis for the collimated high-power laser-diode array stack.

Real-time Reconstruction of Scanned Optical Holograms Using an Electron Beam Addressed Spatial Light Modulator

Real-time holographic recording has recently been demonstrated (1990, Jpn J. appl. Phys., 29 L1840) using the optical heterodyne scanning technique proposed by Poon (1985, Jp. Opt. Soc. Am. A, 2 521). In this paper we discuss the reconstruction of holograms generated by the heterodyne scanning technique. The primary concentration is on real-time reconstruction using an electron beam addressed spatial light modulator (EBSLM). For comparison, coherent reconstruction methods are also presented. Additional topics to be addressed are the spatial frequency limitations of the EBSLM and the derivation of the incoherent point spread function (PSF) of the holographic imaging system. Based upon the derived PSF, the reconstructed real image of a simple slit object is formulated and compared with experimental observations. Descriptions of the scanning holographic recording technique and the operation of the EBSLM are also presented.

Development Of A New Synchroscan Tube Incorporating A Microchannel Plate

In the development of synchroscan tube operated over wide sweeping frequency, multi-pactor discharge which increases back ground noise of the tube, has been investigated in detail. It has been found that the problem of discharge can be solved mainly by suppressing the secondary electron emission from the electrodes in the deflecting section in the tube. On this result, a new synchroscan tube has been developed. This tube can be operated over wide sweeping frequency from 80MHz to 160MHz and the limiting time resolution of the tube itself of about 8ps has been obtained at 80MHz. Driving the tube in synchroscan mode is very easy because the tube has high deflection sensitivity, 50mm/kVp-p. Moreover, this tube incorporating a microchannel plate(MCP) is very high sensitive, by adding the effect of synchroscan mode.

Advances on the fabrication of microchannel plate spatial light modulator based on LiNbO3 waveguide array

Recently, we report a new type of micro channel plate spatial light modulator (MSLM), in which the bulk LiNbO3 crystal plate is replaced by an electro-optic composite material, namely, single crystal waveguide array. This array is a 2D LiNbO3 single crystal waveguide array, which consists of single crystal waveguides with filling materials among adjacent waveguides. Since the dielectric constant of LiNbO3 single crystal is much higher than that of gap filling materials such as polymer/epoxy, the electric field can mostly be constrained inside the crystal material. In addition, by selecting proper opaque filling material, there are also no optical crosstalks among adjacent waveguides. Thus, this special waveguide array works as a 2D set of optically and electrically isolated light guides. While the sensitivity is unchanged, the spatial resolution can be increased. In this paper, a prototype of such a MSLM is presented. The manufacturing processes of the MSLM is introduced. The evaluation on the performance of the MSLM is also reported. The advantages and limitations of the MSLM are addressed.