Okio Yoshida

Calculations of Image Lag in Vidicon-Type Camera Tubes. I. Beam Discharge Lag and Total Image Lag, Including Photoconductive Lag

Image lag in vidicon-type camera tubes is analyzed, taking scanning processes with a low-velocity electron beam into consideration. As the beam landing characteristics, not only usual form of ib=Ibexp (av) but also newly invented one of ib=Ib/{1+exp (-av)} are employed. The latter shows much better agreement to the measured characteristics than the former, but the difference between them is negligible at the regions where image lags become troublesome. First, by expressing target surface potentials and target output currents in exponential forms, the relationship between them is obtained analytically and presented graphically as the target surface potential curves under steady state conditions. Then, the fundamental expressions for beam discharge lag or capacitive lag are obtained for both rise and decay by applying the above-mentioned relationship to transient cases. Finally, the total image lag, including photoconductive lag, is analyzed. From the results obtained by computer calculation, the general features of image lag and the lower limit of image lag are known.

Calculations of Image Lag in Vidicon-Type Camera Tubes. II : Image Lag for Moving Object:Dynamic Image Lag

Image lags with delayed timing where the change of target illumination on a particular element occurs at a somewhat delayed time after the passing of the scanning electron beam are analyzed in vidicon-type camera tubes. Calculated image lags by varying the delayed time are rearranged into spatial order corresponding to the position of picture elements to obtain the dynamic image lags which reveal the pictures of moving objects displayed on a TV monitoring screen. The leading edges of moving bright objects are shown in the smooth rising curve, while their trailing edge are not shown in the smooth decaying curve, but the curves appear in waves, contrary to expectation. This will make the decay lag more objectionable than the rise lag in vidicon performance.

Measurements of Lags in Vidicons Using GaP Red-Emitting Diodes as a Light Source

A novel apparatus for measuring lags in vidicons using GaP red-emitting diodes as a light source is described. By using GaP diodes, the light source becomes compact and the whole measuring system is controllable electrically. Furthermore, measurement can be carried out under the condition of appropriate timing or delayed timing, where the change of light levels occurs just after scanning of the electron beam of vidicons or at a somewhat delayed time. Some of the measured results are also shown.

Target Currents of Vidicons at Slow Scan Performance

ビジコンの緩速走査のターゲット電流について, 通常のフレーム蓄積とともに走査線の重なりから生ずるライン蓄積も考慮した計算式を導いた.式中のフレーム時間の代わりに, これをターゲットの暗時の時定数で割った換算フレーム時間を使用することにより, 計算式とそのグラフ化が簡単になった.グラフとしてターゲット電流一フレーム時間特性と光電変換特性を, 瞬間露光と連続露光の場合について示す.これらのグラフを測定結果と比較することにより, ターゲットの時定数などのパラメーターがわかり, 緩速走査特性の解析に役立てることができる.