Television – Format conversion – Progressive to interlace
Reexamination Certificate
1999-04-01
2003-12-02
Garber, Wendy R. (Department: 2612)
Television
Format conversion
Progressive to interlace
C348S222100
Reexamination Certificate
active
06657674
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image pickup apparatus for producing a video signal from an optical image by driving a solid imaging device and by performing video-signal processing, according to a plurality of scanning systems including a progressive-scanning system.
BACKGROUND OF THE INVENTION
A conventional image pickup apparatus of progressive-scanning type has structure, for example, as shown by the block diagram of FIG.
11
. The conventional image pickup apparatus of
FIG. 11
comprises a charge coupled device (CCD) imaging device
1
that is a solid imaging device of a progressive-scanning type, an imaging device driving circuit (hereinafter referred to as CCD driving circuit)
2
for driving the CCD imaging device
1
, a preamplifier
3
for obtaining a good video signal in regard to signal-to-noise (SN) ratio from the output signal of the CCD imaging device
1
, an analog-to-digital (A/D) converter
4
for converting the output signal of the amplifier
3
to a digital signal, a digital processing circuit
5
a
for providing various video-signal processing on the digital signal, a video tape recorder interface (VTR I/F) circuit
6
for converting the output signal of the digital processing circuit
5
a
to a signal that can be recorded by a VTR
7
that records a progressive-scanning signal, and a progressive-scanning synchronizing signal producing circuit
8
for supplying a progressive-scanning synchronizing signal, by which the output signals of all of the above composing members are synchronized.
The following is description on the operation of the conventional image pickup apparatus. The output signal of the CCD imaging device
1
is produced by performing progressive-scanning on the CCD imaging device
1
according to the progressive-scanning synchronizing signal. The low frequency noise that is included in the output signal of the CCD imaging device
1
is decreased by the preamplifier
3
comprising a correlated-double-sampling circuit. The output signal of the preamplifier
3
is converted to a digital signal by the A/D converter
4
, and undergoes various video-signal processing such as gamma correction, enhancement, matrix processing, and the like in the digital processing circuit
5
a
. The output signal of the digital processing circuit
5
a
is converted by the VTR I/F circuit
6
to the signal that can be recorded by the VTR
7
. In more detail, the VTR
7
records the progressive-scanning video signal of the studio standard of the 525/60P mode, which has 525 horizontal lines, 33.5 kHz horizontal frequency, and 59.94 Hz vertical frequency.
In the above structure, if the frequencies of the synchronizing signals supplied to all composing members including the CCD imaging device is changed to half, the progressive-scanning signal of the 525 horizontal lines, 15.75 kHz horizontal frequency and 29.97 Hz vertical frequency (hereinafter referred to as a 525/30P mode) can be obtained. An image pickup apparatus that is usable for the two modes of the 525/60P mode and the 525/30P mode can be thus obtained.
However, in the image pickup apparatus used for both 525/60P mode and 525/30P mode, the circuits of all composing members are to be operable for the two different modes, which result in extreme difficulty in optimizing the CCD imaging device
1
and the preamplifier
3
. In more detail, the frequencies of two horizontal driving pulses having respectively different phases for reading out by transferring horizontally the signal-electric-charge (hereinafter referred to as signal-charge) that is charged in the CCD imaging device
1
and the frequency of the reset-pulse at the output portion of the CCD imaging device
1
are, in general, as high as 30-50 MHz in the 525/60P mode and 15-25 MHz in the 525/30P mode, though these frequencies are different depending on the number of pixels of the CCD imaging device
1
. Therefore, it is extremely difficult to adjust optimally, for the two different modes, the phase positioning and the waveforms of the above three pulses, which are the factors of determining the performance such as sensitivity, frequency characteristics and the like of the CCD imaging device
1
.
Also, the preamplifier
3
produces a good video signal in regard to SN ratio from the output signal of the CCD imaging device
1
by decreasing the low frequency noise of the output signal in such a manner that the output signal is sampled by using two pulses having respectively different phases, and the difference between the waveforms of the two signal samples, which is a noise component, is eliminated, in which, the phase positioning and the waveforms of the two pulses for the signal sampling are the factors of determining the degree of the improvement of the signal quality in regard to the SN ratio, as in the case of the above CCD driving pulses. In this case also, it is extremely difficult to adjust optimally the phase positioning and the waveforms of the two pulses for the above two different modes, which also makes the circuit complicated.
In addition, for decreasing the influence of the pulses for driving the CCD imaging device
1
and for signal sampling for noise reduction in the preamplifier
3
, filters for intercepting these pulses are used in analog-processing of pre-processing before introducing the signal into the A/D converter
4
. In this case also, since the filters for the above two different modes are needed, the circuit becomes complicated.
The present invention is to address the above problems, i.e., the present invention aims to provide an image pickup apparatus that has a simple circuit and good performance for the use in the two modes of the 525/60P mode and the 525/30P mode, or three modes including one more the 525i mode of interlaced-scanning.
SUMMARY OF THE INVENTION
An image pickup apparatus of the present invention, for realizing the above aim, comprises a signal-charge reading-control circuit for switching either to mode-1 in which one pulse is supplied in each vertical scanning interval (hereinafter referred to as a field) of progressive scanning, or to mode-2 in which one pulse is supplied in every two fields of progressive scanning, for reading out the signal-charge that is charged in a CCD imaging device as the output signal of the CCD imaging device, a writing-control circuit that works for writing, into a memory, the output signal of the CCD imaging device, during the intervals when the output signal is obtained by reading out the signal-charge that is charged in the CCD imaging device, and, a reading-control circuit that works for reading out, in the mode-1, the signal written in the memory according to a progressive-scanning synchronizing signal, and for reading out, in the mode-2, the signal written in the memory according to an interlaced-scanning synchronizing signal in such a manner that odd scanning lines (hereinafter referred to as “line” for “scanning line”) are read out in each odd field and even lines are read out in each even field. The above structure enables the image pickup apparatus to have a simple circuit and good performance for the use in the two modes of the 525/60P mode and the 525/30P mode. More details are described hereinafter.
A first invention of the present invention is that the image pickup apparatus comprises a CCD imaging device, a progressive-scanning synchronizing signal producing circuit for supplying a progressive-scanning synchronizing signal, an interlaced-scanning synchronizing signal producing circuit for supplying an interlaced-scanning synchronizing signal having a vertical synchronizing signal of the frequency that is identical with the frequency of the vertical synchronizing signal of the progressive-scanning synchronizing signal, and a horizontal synchronizing signal of the frequency that is substantially the half of the frequency of the horizontal synchronizing signal of the progressive-scanning synchronizing signal, an imaging-device driving circuit for supplying a driving signal for performing scanning on the CCD imaging device according to the progre
Asada Ryoji
Nishikawa Shoji
LandOfFree
Image pickup apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image pickup apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image pickup apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3168616