Histogram generator

Details Histogram generator Histogram generator

1998-03-04

2001-06-26

Tran, Phuoc (Department: 2621)

Image analysis

Histogram processing

Reexamination Certificate

active

06252983

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of histogram generators, and particularly to the detection of distribution of levels of input data such as input video signals.
BACKGROUND OF THE INVENTION
In general, histograms are created in a signal processing circuit for television signals to extract the characteristics of video signals. Applied technology for creating histograms has been introduced in the past. One example of a device employing such technology is disclosed in Japanese Laid-open Patent No. S58-63989.
FIG. 17
shows an example of a histogram which divides sampled input signals into more than one group based on the size of sample value. In
FIG. 17
, sampled signals are divided into four groups. In order to group the sample values, thresholds a
1
, a
2
, and a
3
are set, and four intervals, S
1
, S
2
, S
3
and S
4
are then formed in accordance with these thresholds. Continuous input video signals are sampled and sample values allocated to one of the intervals S
1
, S
2
, S
3
, and S
4
. A histogram is created based on the intervals S
1
, S
2
, S
3
, and S
4
, and the counted number of samples (frequency) allocated to each intervals.
In a histogram generator such as the one of the aforementioned patents, however, the created histogram may be unstable. A sample value of the input signal that lies in small neighborhood of the threshold al may be judged by the histogram generator as belonging to the interval S
1
at one moment while judged as belonging to the interval S
2
at another moment, due to factors like noise.
SUMMARY OF THE INVENTION
A histogram generating apparatus according to the present invention finds a frequency of an input video signal level by dividing a maximum range of the input signal level into several intervals using several threshold values as boundaries. The histogram generating apparatus comprises a weighting circuit for weighting samples occurring near a threshold value and a counting circuit for counting the output signals of the weighting circuit.


REFERENCES:
patent: 5594807 (1997-01-01), Liu
patent: 5808697 (1998-09-01), Fujimura et al.
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patent: 01082288 (1989-03-01), None

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