To have higher resolution of distance in the laser scanner using the phase demodulation method, signal should be modulated with a high frequency. In the signal processing of modulation and demodulation, it is inevitable to amplify the signals. However, it is not easy to amplify the high frequency since the amplifying gain is restricted by the frequency bandwidth. It is advantageous to demodulate using an intermediate frequency in which high gain amplification as well as less contaminated signal is obtained. Analytical and experimental results are presented to show how the intermediate frequency demodulation method works and how good performance is obtained in the time and frequency domains.

The homodyne interferometer has the advantages of simple optical configuration and low cost. However, it requires a caution in using an electronic filter such as high pass filter (HPF) to get rid of low frequency electronic noises and the dc offset associated with the optical intensity in the photodiode electronic circuitry. When the vibration amplitude is smaller than at least 12 of the wavelength of He-Ne laser, a problem of incorrect velocity or distorted velocity measurement can be caused since a dc value of the interference signal is eliminated by using the HPF. To solve this problem of using the HPF in the homodyne interferometer, a synthetic interferometer using a mechanical modulation method is proposed in this work by exciting a reference mirror with the displacement larger than 12 of the wavelength. In this work, the analytical work is presented to show how the synthetic interferometer solves the problem of incorrect velocity measurement by using the Fourier-Bessel function description of the interference signals. Simulation and experimental works are also presented to validate the synthetic heterodyne interferometer proposed in this work.

Projection images of a metal mesh produced by directional MeV electron beam together with directional proton beam, emitted simultaneously from a thin foil target irradiated by an ultrashort intense laser, are recorded on an imaging plate for the electron imaging and on a CR-39 nuclear track detector for the proton imaging. The directional electron beam means the portion of the electron beam which is emitted along the same direction (i.e., target normal direction) as the proton beam. The mesh patterns are projected to each detector by the electron beam and the proton beam originated from tiny virtual sources of ~20 µm and ~10 µm diameters, respectively. Based on the observed quality and magnification of the projection images, we estimate sizes and locations of the virtual sources for both beams and characterize their directionalities. To carry out physical interpretation of the directional electron beam qualitatively, we perform 2D particle-in-cell simulation which reproduces a directional escaping electron component, together with a non-directional dragged-back electron component, the latter mainly contributes to building a sheath electric field for proton acceleration. The experimental and simulation results reveal various possible applications of the simultaneous, synchronized electron and proton sources to radiography and pump-probe measurements with temporal resolution of ~ps and spatial resolution of a few tens of µm.

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