The electro-optic coefficient γ63 of ADP crystal which is significant in the application of electro-optic effect of the basal section of ADP is measured by a static method of reading the voltage required to produce a half wave retardation. Besides the value of γ63 its relation to wavelength is also treated. It is recognized that the voltage required to produce a half wave retardation has linear relation to wavelength, and that the value of γ63 decreases about 2% in the range 400_??_600 nm. In the experiment two basal sections of ADP were used and the measured voltage was that produced a quarter wave retardation to each crystal, because in order to get high sensitivity in measuring the voltage of a half wave retardation it was necessary to raise the voltage to that of nearly three quarter wave retardation and the voltage of break down around the edge of crystal was no more than 11000 volt. About the errors caused by difference of the orientation of two crystals and by discord of the direction of beam and the Z-axis of the crystal are discussed rather minutely. The gaps between electrodes and crystal were filled with gel composed of sodium stearate dissolved in glycerine with polyvinyl alcohol.
Employing ADP crystals as light-modulators with frequency selecting characteristics which are caused by the mechanical resonance of the crystals, an instantaneously recording type speech sound analyser and a synthesizer controlled by the visible-speech pattern have been devised. Simple tentative sets of the analyzer and the synthesizer by this principle have been constructed and successful results have been obtained. This synthesizer has seven main (timbre) channels and a separate subsidiary channel for the signal controlling the fundamental pitch of the voice source or introducing the noise (hiss) source as prescribed. As a more useful apparatus, a practical design of the analyser-synthesizer which is now under' construction by the authors is given. The optical system comprises 25 timbre channels (including 25 resonators with consecutively different resonance frequencies around 45 kc/s) and three subsidiary channels for pitch, hiss and total intensity signals. The same opticalsystem is utilized both for the analyser and for the synthesizer. By this apparatus, the speech with any length is analysed and recorded on a running photographic film simultaneously as spoken, and after developing the pattern, the recorded film is driven by the same driving system, thus the original speech being played back. The revision of any particularly interested features, such as pitch inflections, stresses, spike or hiss characteristics, transients of the formants etc. can be made on the recorded (or originally hand-painted) pattern. The speed of the speech on the play back can be changed as desired. The possibility of the application of this system to the vocoder is also discussed.