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DESCRIPTION JPS62171292

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DESCRIPTION JPS62171292
[0001]
The present invention relates to a frequency separation type color signal separation circuit used
in combination with a solid-state imaging device. (2) Conventional Technology The circuit shown
in FIG. 3 is used as a circuit for frequency separating a luminance signal and a color signal from
the output of a solid-state imaging device. In the circuit shown in FIG. 3, the luminance signal
present in the low frequency region using the difference between the frequency of the luminance
signal supplied from the solid-state imaging device 1 and the frequency of the color signal is lowpass filter 2 and the color existing in the high frequency region Signals are respectively extracted
by the band pass filter 3. (3) Problems to be Solved by the Invention In the circuit shown in FIG.
3, when an object with clear contrast is picked up, a false signal due to ringing or the like is
generated in the color signal under the influence of the luminance signal. There is a problem of
that. If this is shown by a signal waveform, it will become like FIG. That is, when the output signal
of the solid-state imaging device 1 at the time of imaging a subject whose brightness is clear is
the signal A (FIG. 4 (a)), the luminance signal B has a rectangular wave as shown in FIG. become.
In the color signal C at this time, as shown in FIG. 4C, the rising and falling of the luminance
signal B cause ringing, and a false signal is generated over T1 during lj1. Therefore, when a video
camera of a frequency separation system captures an image of a subject with clear contrast, an
accurate color signal can not be obtained. (4) Means for Solving the Problems The present
invention has been made in view of the above points, and it is an object of the present invention
to suppress a false signal due to ringing or the like generated in a color signal when imaging a
subject with clear contrast In order to achieve this purpose, a clamp circuit for clamping the
output of the solid-state image sensor and a sample-hold circuit for sampling and holding the
output of the solid-state image sensor with reference to the output of the clamp circuit are
provided. ing. (5) Operation With this configuration, the clamp circuit and the sample hold circuit
operate to operate alternately at the color signal carrier frequency. (6) Embodiment The present
18-04-2019
1
invention utilizes that the color signals included in the frequency separation type solid-state
imaging device output are expressed as the level difference between adjacent signals output in
time series. Hereinafter, the present invention will be described based on the drawings. FIG. 1 is a
telok diagram showing an embodiment of a color signal separation circuit according to the
present invention. In the figure, the same components as in FIG. 3 are given the same reference
numerals, and the description thereof is omitted. In FIG. 1, the output of the solid-state imaging
device 1 is supplied to a low pass filter 2, a clamp circuit 5, and a sample hold circuit 6.
The clamp circuit 5 clamps the output signal A of the solid-state imaging device 1 for each clock
signal 1+ (FIG. 2 (b)). The sample and hold circuit 6 samples and holds the output signal A of the
solid-state imaging device 1 based on the output of the clamp circuit 5 in the clock signal t2 (FIG.
2 (b)). The frequencies of these clock signals 1 and t2 are matched to the carrier frequency of the
color signal, and they are mutually out of phase so that the clamping operation and the sample
and hold operation are alternately performed. By the clamp operation of the clamp circuit 5 and
the sample hold operation of the sample hold circuit 6, a color signal shown in FIG. 2 (d) is
obtained from the sample hold circuit 6. According to this color signal, a false signal is generated
at the rising and falling portions of the output signal of the solid-state imaging device 1, but it
returns to a normal color signal one cycle after the rising or falling. It is possible to suppress
generation of a false signal during T2 (FIG. 2 (d)), and a false signal is generated over a long
period of time T1 as in the color signal by the conventional circuit shown in FIG. Can be
prevented. (7) Effects of the Invention As described above, the present invention comprises a
clamp circuit for clamping the output of the solid-state imaging device, and a sample hold circuit
for sampling and holding the output of the solid-state imaging device based on the output of the
clamp circuit. Since the clamp circuit and the sample and hold circuit are alternately operated at
the color signal carrier frequency, false signals due to ringing or the like generated in the color
signal can be suppressed when an object with clear contrast is captured. It becomes possible.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram showing an embodiment of a color signal separation circuit according to the
present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3
is a block diagram showing a conventional color signal separation circuit. FIG. 4 is a waveform
diagram for explaining the operation of the circuit shown in FIG.
18-04-2019
2
1 solid image pickup element 2 low pass filter 3 band pass filter 5 clamp circuit 6 sample and
hold circuit patent applicant Nippon Electric Home Electronics Co., Ltd. Attorney Attorney Yama
1) Takeshi Tree Fig. 2 (b) t2 tttt ↑ Fig. 3 J @ 4 Fig. 2 T 1-1
18-04-2019
3
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