Daewoo DTK-28 Series, Service Manual, Page: 52 / 71

CP-850/F Service Manual
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5.3.2.5 Luma Sharpness Enhancer (LSE)
Sharpness is one of the most critical features for optimum picture quality. This important processing is performed in the
LSE circuitry of DDP 3315C. It consists of the dynamic peaking, the luma transient improvement (LTI) and an adaptive
mixer. The luma input signal is processed in the peaking and LTI block in parallel. Both output signals are combined in
the mixer depending on the selected LSE characteristic.
5.3.2.6 Dynamic Peaking
The dynamic peaking improves the details of a picture by contour emphasis. It adapts to the amplitude and the
frequency of the input signal. Small detail amplitudes are sharpened, while large detail amplitudes stay nearly
unmodified.
5.3.2.7 Luma Transient Improvement (LTI)
For small detail amplitudes the dynamic peaking is the most appropriate processing to improve the sharpness.
However, for large amplitudes even small over-and/ or undershoots of the peaking are too annoying. The luma transient
improvement enhances the slope of picture detail without these effects by a non-linear processing. The contour
correction signal calculated in this block, is limited to the adjacent extreme values to prevent over- and undershoots.
The LTI features an adjustable gain control and an adjustable coring threshold to prevent the enhancement of small
noise amplitudes.
5.3.2.8 Mixing of Dynamic Peaking and LTI
The contour correction signals of the dynamic peaking and the LTI block are combined by the mixer. Controlled by the
amplitude of a picture edge, this circuitry fades between these two signals. Thus, small and medium picture detail is
enhanced by contour emphasis (peaking) and large picture detail is enhanced by step-improvement (LTI).
5.3.2.9 Chroma Transient Improvement
The intention of this block is to enhance the chroma resolution. A correction signal is calculated by differentiation of the
colour difference signals. The differentiation can be selected according to the signal bandwidth, e.g. for
PAL/NTSC/SECAM or digital component signals, respectively. The amplitude of the correction signal is adjustable.
Small noise amplitudes in the correction signal are suppressed by an adjustable coring circuit. To eliminate “wrong
colours”, which are caused by over and undershoots at the chroma transition, the sharpened chroma signals are limited
to a proper value automatically.