Television – Camera – system and detail – Optics
Reexamination Certificate
1998-10-16
2003-07-01
Christensen, Andrew (Department: 2615)
Television
Camera, system and detail
Optics
C348S229100, C348S230100
Reexamination Certificate
active
06587149
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a video camera and, more particularly, to a video camera that can perform enlargement of dynamic range of such as a video movie, successive picturing of frame still images, and enlargement of dynamic range of frame still images.
DESCRIPTION OF PRIOR ART
Operation of Prior Art
As a method for enlarging the dynamic range of a video camera, there is a method which is described in Japanese Published Patent Application No. Hei 6-13207. In this method, a first exposure signal such as a long term exposure signal (hereinafter, “Slong signal”) and a second exposure signal such as a short term exposure signal (hereinafter, “Sshort signal”) are synthesized, thereby enlarging the dynamic range on appearance.
This method will be briefly described with reference to the drawings.
FIG. 17
is a block diagram illustrating an example of construction of a prior art video camera
6
.
FIG. 18
is a diagram schematically showing the storage state and transferring state of Slong signals and Sshort signals which are light-electricity converted by a progressive scanning CCD
11
in the prior art video camera.
This video camera
6
is constituted by a taking lens
10
, a progressive scanning CCD
11
, a switch
12
, a signal synthesizing means
18
, and a camera signal processing part
20
.
In addition, the progressive scanning CCD
11
is constituted by light-electricity conversion parts
50
, vertical transfer parts
52
transferring charges in the vertical direction, which charges are transferred from the light-electricity conversion parts
50
, a horizontal transfer part
54
which outputs serially in the horizontal direction the charges which are transferred from the vertical transfer parts
52
, and an output amplifier
56
which amplifies output of the horizontal transfer part
54
.
The light-electricity conversion part
50
comprises photodiodes
51
, the number of which corresponds to the pixel number, and the vertical transfer part
52
comprises a plurality of CCD
53
which are respectively vertically arranged respectively corresponding to the photodiode
51
.
While in
FIG. 18
an array which has 4 rows of pixels and 6 columns of pixels is illustrated, in an actual construction of such as VGA (Video Graphics Array), a construction which has 640 rows of pixels and 480 columns of pixels is adopted.
In the video camera
6
constructed as above, the light incident to the video camera through the taking lens
10
is light-electricity converted in the progressive scanning CCD
11
.
In other words, in this progressive scanning CCD
11
, as shown in
FIG. 19
, in the period of one field, i.e., the vertical scanning period (hereinafter also referred to as “1V”), the exposure time is switched between the long exposure time T1′ and the short exposure time T2′ by means of an electronic shutter (not shown here) so that the exposure amount against the light-electricity conversion part
50
in the progressive scanning CCD
11
may be different.
Here, T1′ is set to about {fraction (1/60)} second, and T2′ is set to about {fraction (1/1000)} second. Video images of one screen are respectively imaged during T1′ and T2′, thereby outputting a signal to the vertical transfer part
52
at the timing shown in FIG.
19
. The signal read out during T1′ becomes a Slong signal and the signal read out during T2′ becomes a Sshort signal.
The Slong signals and the Sshort signals which are obtained with light-electricity converted by the respective photodiodes
51
of the light-electricity conversion part
50
are read out to the vertical transfer part
52
as shown by arrows in the figure so that outputs from the upper and lower photodiodes
51
which are adjacent each other are added respectively, in a vertical blanking period (in this case during T1′-T2′). Therefore, in the vertical transfer part
52
, the Slong signal and the Sshort signal are respectively stored at the position of CCD
53
designated by a black circle and at the position of CCD
53
designated by a white circle, alternatingly.
Therefore, the respective Slong signal and Sshort signal stored in the vertical transfer part
52
are transferred alternatingly to the horizontal transfer part
54
by line by line, and thereby they are output from the light-electricity conversion part
50
through the output amplifier
56
. Accordingly, when, for example, the progressive scanning CCD
11
comprises 480 pixels in the vertical direction, Slong signals of 240 lines and Sshort signals of 240 lines are respectively output from the light-electricity conversion part
50
in the period of one field, i.e., 1V.
After the Slong signal and the Sshort signal, which are serially output line by line from the progressive scanning CCD
11
, are separated into the Slong signal and the Sshort signal by the switch
12
, these signals are synthesized in the signal synthesizing means
18
to be output to the camera signal processing part
20
as a signal of one series. Accordingly, in the case of non-interlacing system, the above example results in synthesized signals of 240 lines (hereinafter, “Smix signal”) in the period of one field, i.e., 1V.
Here, while as shown in
FIG. 20
the above Slong signal is saturated at the light incident amount of L1′ due to the large exposure amount, this Slong signal has a large change of signal level at the light incident amount below that, thereby resulting in a preferred S/N ratio and keeps the gradation at the low luminescent part.
On the other hand, while the Sshort signal has low gradation at the low luminescent part due to the low exposure amount, it keeps the gradation without saturating up to the high luminescent part on the contrary. Therefore, the gradation characteristics of the Smix signal, which has synthesized the both, is enlarged relative to the gradation characteristics of the Slong signal only, and thus, the dynamic range on appearance is enlarged.
In this way, the Smix signal whose dynamic range is thus enlarged by the signal synthesizing means
18
is processed to a video signal which is adaptive to the television display (such as NTSC system) by the camera signal processing means
20
, and is output to the outside.
PROBLEMS TO BE SOLVED
However, the above-described prior art video camera
6
has the following problems.
First of all, since in the prior art video camera
6
T1′ is set to {fraction (1/60)} sec. and T2′ is set to {fraction (1/1000)} sec. as described above, the enlargement rate (&thgr;1′/&thgr;s′) of dynamic range in this case is about 16 times [≈({fraction (1/60)})/({fraction (1/1000)})].
However, when T2′ is quite a short time, such as when T2′ is {fraction (1/1000)} sec., not only the S/N ratio of the Sshort signal itself is insufficient but also the gradation of the video image imaged by the video camera
6
becomes insufficient as well.
In other words, in case where such enlargement rate of dynamic range amounts to about 16, and when the scenery inside the room and that outside as shown in
FIG. 21
are imaged together, while the video images of the clear part
72
(scenery outside) and of the dark part
71
(inside the room) are obtained as clear ones, the video images of the intermediate part
73
(periphery of a window, such as a desk adjacent to the window) for which the enlargement rate of dynamic range of about 2~4 times is made the most appropriate cannot be made clear images due to the too large enlargement rate of dynamic range in the prior art device, thereby resulting in a large problem.
With reference to
FIG. 20
, this problem is explained as a fact that when the light incident amount is within a range of L1′ to L2′, since the signal level of the Sshort signal at that timing is low while the Slong signal is saturated, the S/N ratio is deteriorated, whereby the Smix signal is affected by noise components to result in non-preferred video images.
In the above-described prior art video camera
6
, when the progressi
Nakayama Masaaki
Toyomura Kohichi
Yamamoto Yasutoshi
Yoneyama Masayuki
Christensen Andrew
Harris Tia M.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Video camera with progressive scanning and dynamic range... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Video camera with progressive scanning and dynamic range..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Video camera with progressive scanning and dynamic range... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3076654