| 摘要 |
PURPOSE:To record gradation of a picture correctly by making gamma- correction beforehand every time when using, and keeping the maximum value and minimum value of beam current constant during recording operation, and thereby removing variation of intermediate value of beam current due to temperature change in initial stage of operation. CONSTITUTION:A change-over switch 18 is made to the state of switching as shown in the figure, and reference staircase wave voltage SR is supplied from a staircase wave generator 19 to a gamma correcting circuit 17. When input/output characteristic of the gamma correcting circuit 17 is set to conform with input/output characteristic of an EBR 1, the change-over switch 18 is set to the state reverse to that shown in the figure, and video signals from an input terminal 10 are supplied to the grid 3 of the electron beam picture recording device EBR 1, and recorded in a film F making electron beam Br a stylus. In this case, the maximum value and minimum value of beam current are kept constant, and intermediate value is regulated by set input/output characteristic of the gamma correcting circuit 17. Therefore, it is not influenced by temperature change of the EBR 1 in initial stage of operation.
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