Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1999-09-25
2002-04-30
Ho, Tuan (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S234000
Reexamination Certificate
active
06380974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital video camera and, more particularly, to an apparatus suitably used in a video camera apparatus for converting an analog video signal obtained by an image pickup element into a digital video signal and performing digital signal processing.
2. Related Background Art
FIGS. 1A and 1B
show a conventional video camera apparatus for A/D-converting an analog signal output from a solid-state image pickup element, and performing signal processing in a digital form. Referring to
FIGS. 1A and 1B
, a video signal obtained via a lens element
1
, a solid-state image pickup device
2
, a correlation double sampling circuit
3
, and a gain adjustment circuit
4
is sampled by an A/D converter
5
to be converted into a digital signal.
The sampled digital signal is supplied to a digital signal processing circuit
6
. The digital signal processing circuit
6
generates a digital luminance signal and digital color-difference signals from the input digital signal. The digital luminance signal generated by the digital signal processing circuit
6
is converted into a band-limited analog luminance signal via a D/A converter
12
and a low-pass filter
13
.
The digital color-difference signals are converted into band-limited analog color-difference signals via D/A converters
35
and
36
and low-pass filters
37
and
38
. Furthermore, the analog color-difference signals are supplied to a modulation circuit
39
to be converted into an analog chrominance signal. The analog chrominance signal is supplied to a digital signal recording device
21
together with the analog luminance signal. The processing so far is executed at the sampling frequency of the image pickup element.
When YC-separated input signals are externally input as a video signal, these signals are respectively input to switch circuits
8
and
9
. When a composite video signal VIDEO is input, the signal VIDEO is separated into luminance and chrominance signals by a luminance/chrominance separation circuit
7
, and the separated signals are input to the switch circuits
8
and
9
. One of these YC-separated input signals and the composite video signal is selected by the switch circuits
8
and
9
.
The analog luminance and color-difference signals from a camera and externally input analog luminance and color-difference signals are selected by switch circuits
14
and
15
. The frequency band of the analog luminance signal is limited by a low-pass filter
17
. The band-limited analog luminance signal is supplied to an A/D converter
18
to be converted into a digital luminance signal.
The analog chrominance signal is converted into analog color-difference signals by a demodulation device
40
, and the analog color-difference signals are then converted into digital color-difference signals by A/D converters
41
and
42
. In this case, the A/D conversion is performed at the sampling frequency of a digital VTR.
The digital signal recording device records the digital luminance and color-difference signals, which are converted, as described above, on a magnetic tape
22
. Thus, a digital video signal is recorded.
At this time, switch circuits
25
and
26
are switched to the REC side, and the analog luminance and chrominance signals are selected and output by the switch circuits
25
and
26
. An EVF
33
performs a display operation based on the output luminance and chrominance signals for monitoring an image pickup operation.
In a reproduction mode, the digital signal recording device
21
generates digital reproduced luminance and color-difference signals from a signal reproduced from the magnetic tape
22
. Of these signals, the reproduced luminance signal is converted into an analog luminance signal by a D/A converter
23
which operates at the sampling frequency of the digital VTR, and thereafter, the frequency band of the analog luminance signal is limited by a low-pass filter
24
, thus obtaining an analog reproduced luminance signal.
On the other hand, the digital color-difference signals are converted into analog color-difference signals by D/A converters
28
and
29
which operate at the sampling frequency of the digital VTR. The frequency bands of these analog color-difference signals are then limited by low-pass filters
30
and
31
to obtain an analog reproduced color-difference signal. Furthermore, the analog reproduced color-difference signal is modulated by a modulation device
32
.
At this time, the switch circuits
25
and
26
are switched to the PB side, selecting the modulated analog reproduced color-difference signals together with the analog reproduced luminance signal, and output these signals as a reproduced video signal.
In the case of the conventional digital video camera apparatus shown in
FIGS. 1A and 1B
, in order to allow recording/reproduction of both digital luminance and color-difference signals from the camera and external analog luminance and color-difference signals, many A/D converters, D/A converters, and the like are required. For this reason, the circuit scale constituting the digital video camera apparatus becomes large, and it is difficult to reduce cost.
In conventional image pickup recording apparatuses adopting a digital signal processing system, an image pickup signal processing circuit is an analog circuit, and an output signal from the analog processing circuit is converted into a digital signal. For this reason, due to a large circuit scale, the number of components becomes large, and current consumption undesirably increases. Also, it is difficult to make the apparatus compact, and to reduce cost.
Since the apparatus includes both an analog signal processing circuit and a digital signal processing circuit, a sufficient S/N ratio cannot often be obtained due to interference such as mixing of a digital signal into an analog signal, and the apparatus cannot be rendered compact.
Since the image pickup signal processing circuit adopts analog processing, image quality is determined by performance such as the frequency characteristics, noise characteristics, a change in performance due to a change in temperature, a variation in characteristics in units of circuits, and the like, and it is difficult to achieve high image quality.
In order to attain special effects using a frame memory and a digital calculation, a still larger number of circuit components are required. As a result, it is difficult to make the apparatus compact, and power consumption undesirably increases.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-mentioned problems, and has as its object to simplify the circuit arrangement of a digital video camera apparatus which selects one of a video signal from a digital video camera and a video signal from an external input terminal, and records the selected video signal on a recording medium.
The present invention has been made to solve the above-mentioned problems, and has as its another object to provide a digital video camera apparatus having a small number of components.
The present invention has been made in consideration of the above-mentioned problems, and has as its still another object to simplify the circuit arrangement of an apparatus for digitally recording an image pickup signal.
In a digital video camera apparatus according to an aspect of the present invention, which comprises a digital signal processing circuit and a digital signal recording device and in which an analog video signal supplied from an image pickup element is converted into a digital video signal, the converted digital video signal is supplied to the digital signal processing circuit, and the digital signal recording device records the digital video signal on a recording medium after predetermined signal processing, and of signals to be supplied from the digital signal processing circuit to the digital signal recording device, a luminance signal is supplied in a state of an analog signal and a chrominance signal is supplied in a state of a digital signal.
Accor
Hieda Teruo
Kawahara Norihiro
Ueda Osamu
Ho Tuan
Morgan & Finnegan L.L.P.
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