Television – Synchronization – Sync separation
Reexamination Certificate
1999-09-10
2004-09-21
Garber, Wendy R. (Department: 2612)
Television
Synchronization
Sync separation
C348S521000
Reexamination Certificate
active
06795124
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera system and, more particularly, to an external synchronization camera system using a composite synchronization signal containing a horizontal synchronization signal and a vertical synchronization signal provided as a system synchronization signal from an external source.
2. Description of the Related Art
In a monitoring camera system, usually, a slave camera is synchronized by using synchronization signals (a horizontal synchronization signal HD, a vertical synchronization signal VD, and a composite synchronization signal SYNC containing these signals) for a master camera. This is a well-known technique called “external synchronization”. In this external synchronization, a process is performed for causing the phase of the synchronization signal of the slave camera to coincide with that of the synchronization signal of the master camera. At this time, ultimately, video signals are input from a plurality of cameras to one monitor.
However, depending on the location at which the slave camera is disposed, the time required for the synchronization signal of the master camera to reach each slave camera differs. If locked as it is, an out-of-synchronization video is produced on the monitor. For this reason, in each slave camera, adjustments are made so that out-of-synchronization does not occur on the monitor by phase-shifting a synchronization signal provided from the master camera so as to absorb out-of-synchronization portions which occur on the monitor.
When out-of-synchronization adjustments by this phase shift are made, two methods are available: a method in which a horizontal synchronization signal HD and a vertical synchronization signal VD are used as synchronization signals provided from the master camera, and a method in which a composite synchronization signal SYNC containing a horizontal synchronization signal HD and a vertical synchronization signal VD is used.
FIG. 8
shows each waveform of the horizontal synchronization signal HD, the vertical synchronization signal VD, and the composite synchronization signal SYNC of the EIA (Electronic Industries Association) method (NTSC (National Television System Committee)-compatible black-and-white method). Generally speaking, the synchronization signal provided from the master camera is input to a timing controller IC within the slave camera. The construction of a camera system for each method is described below.
First, referring to
FIG. 9
, a description is given of a camera system using a horizontal synchronization signal HD and a vertical synchronization signal VD as synchronization signals provided from the master camera. In
FIG. 9
, an output signal of a CCD image pickup device
101
is input to a signal processing IC
102
whereby various signal processings are performed thereon, after which the signal is output as a video signal Video-OUT. A timing controller IC
103
generates a CCD driving signal for driving the CCD image pickup device
101
, a signal processing driving signal for driving the signal processing IC
102
, etc.
Here, the horizontal synchronization signal HD (master HD) and the vertical synchronization signal VD (master VD) provided from the master camera are input to the timing controller IC
103
after passing through an HD phase adjusting circuit
104
and a VD phase adjusting circuit
105
. Then, the external vertical synchronization signal VD is provided to a V period counter
106
, as a reset signal therefor, within the timing controller IC
103
. The V period counter
106
counts up for each horizontal scanning period (
1
H) and generates an internal vertical synchronization signal VD′.
On the other hand, in a phase comparator
107
within the timing controller IC
103
, the external horizontal synchronization signal HD is compared in phase at the rise edges with an internal horizontal synchronization signal HD′ which is generated by an internal HD generating circuit
108
. This comparison result of the phase comparator
107
is provided to a PLL circuit
109
. The PLL circuit
109
outputs a DC voltage corresponding to the comparison result of the phase comparator
107
and applies it across both ends of a variable-capacity diode
111
of a clock oscillator
110
which generates a clock 2MCK of a frequency twice as high as the master clock MCK which is a reference clock of this camera system.
In the camera system constructed as described above, phase shift for the external horizontal synchronization signal HD and the external vertical synchronization signal VD provided from the master camera is performed by the HD and VD phase adjusting circuits
104
and
105
before these signals are input to the timing controller IC
103
. For the phase shift, generally, an analog monostable multivibrator having a simple circuit configuration is used.
This analog monostable multivibrator is capable of changing the phase of a signal by providing a fixed amount of a delay with respect to the fall or rise of the signal. Therefore, as is clear from the waveform chart of
FIG. 8
, phase adjustments can be performed on the horizontal synchronization signal HD and the vertical synchronization signal VD having a fixed period by the HD and VD phase adjusting circuits
104
and
105
using an analog monostable multivibrator, respectively.
Next, referring to
FIG. 10
, a description is given of a camera system using a composite synchronization signal SYNC as a synchronization signal provided from the master camera. In
FIG. 10
, an output signal of a CCD image pickup device
201
is input to a signal processing IC
202
whereby various signal processings are performed thereon and then the signal is output as a video signal Video-OUT. A timing controller IC
203
generates a CCD driving signal for driving the CCD image pickup device
201
, a signal processing driving signal for driving the signal processing IC
202
, etc.
Here, the composite synchronization signal SYNC (master SYNC signal) provided from the master camera is input to the timing controller IC
203
, and the signal is separated into a horizontal synchronization signal HD and a vertical synchronization signal VD by a synchronization separation circuit
204
within the relevant IC
203
. Then, the separated external vertical synchronization signal VD is provided to a V period counter
205
, as a reset signal therefor, within the timing controller IC
203
. The V period counter
205
counts up for each horizontal scanning period and generates an internal vertical synchronization signal VD′.
On the other hand, in a phase comparator
206
, the separated external horizontal synchronization signal HD is compared in phase at the rise edges with an internal horizontal synchronization signal HD′ which is generated by an internal HD generating circuit
207
. This comparison result of the phase comparator
206
is provided to a PLL circuit
208
. The PLL circuit
208
outputs a DC voltage corresponding to the comparison result of the phase comparator
206
and applies it across both ends of a variable-capacity diode
210
of a clock oscillator
209
which generates a clock 2MCK of a frequency twice as high as the master clock MCK which is a reference clock of this camera system.
In a manner as described above, in the camera system of the former case using a composite synchronization signal SYNC as a synchronization signal provided from the master camera, as is clear from the waveform chart of
FIG. 8
, the composite synchronization signal SYNC has mixed synchronization signals of a 1H period and a 1/2H period, and the period of the composite synchronization signal SYNC is irregular; it is thereby impossible to directly perform phase adjustment on the composite synchronization signal SYNC by using an analog monostable multivibrator before the signal is input to the timing controller IC
203
.
Therefore, when phase adjustment is required in this type of camera system, as shown in
FIG. 11
, it is necessary to separate the composite synchronization sign
Gamo Naoyasu
Sato Masa-aki
Frommer William S.
Frommer & Lawrence & Haug LLP
Garber Wendy R.
Rosendale Matthew L
Smid Dennis M.
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