| 摘要 |
An aperture compensating circuit for enhancing the contour compensating in the picture and S/N ratio is disclosed. The aperture compensating circuit comprises a means for separating the luminance signal from the input signal, sample and hold means for sampling, holding and switching the luminance signal level input to the monitor with two times subcarrier frequency, 2 fs, a first control means for controlling the aperture edge quantity to emphasize the contour signal according to the value of the level output from the sample and hold means, a clamping means between the sample/hold means and a second control means to prevent the unstablization of the luminance signal level due to a distribution level between a source and a gate of the field effect transistor in the sample/hold means by clamping the source stage of said field effect transistor; and a second control means for controlling the aperture edge quantity in such a manner that when the edge quantity is controlled by the first control means, if the level of the luminance signal is high, the edge quantity is to be increased regardless of the difference of the luminance levels within the 1 H period, while if the level of the luminance signal is low, the edge quantity is to be decreased.
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