Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1998-10-02
2003-06-03
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S241000, C348S229100, C348S230100
Reexamination Certificate
active
06573933
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image processing apparatus as well as to an image processing method for processing image signals transmitted from an image pick-up tube or an image pick-up element, and more specifically to an image processing apparatus and an image processing method for suppressing flickers of a fluorescent lamp as well as to a computer-readable recording medium with a program for making a computer execute the method stored therein.
BACKGROUND OF THE INVENTION
Generally a television camera (an image pick-up device) for picking up image of an object converts pixel information to an image signals for enabling reproduction of an image on a television receiver. In this step, the pixel information is expressed with brightness values for pixels two-dimensionally distributed, and the television camera (an image pick-up device) converts the pixel information to one-dimensional image signals based on a prespecified transmission system.
In a television system, generally luster scanning is employed as processing for conversion to one-dimensional image signals, namely as scanning, and basically image information for an entire screen is fetched by means of horizontal scanning for fetching a brightness value or color information at each pixel position on a screen and vertical scanning for repeatedly executing the horizontal scanning from a top to a bottom of a screen. Especially skip scanning is executed in which the horizontal scanning is executed for every n−1 scanning lines and the vertical scanning is executed n times for the entire screen. To form a screen, namely one frame in the skip scanning, n times of vertical scanning, namely n fields are required.
As a transmission system for a color television currently being used, there are the three systems of NTSC system, PAL system, and SECAM system, but herein consideration is made for a case,where the NTSC system is employed.
In the NTSC system, the number of scanning lines is 525 lines, and one frame comprises two fields, one consisting of an odd number field and another consisting of an even number field. Also in the NTSC system, a frame frequency is 30 Hz, namely scanning is executed at a rate of 60 fields per second.
When picking up image of an object using an analog type of image pick-up tube as a television camera based on this NTSC system and a fluorescent lamp using a 50 Hz power as illumination, image signals each including twinkling with a constant cycle, namely flickers are generated.
FIG. 7
is an explanatory view for illustrating field scanning in a television camera using a 50 Hz power fluorescent lamp and executing scanning at a rate of 60 fields per second and flickers generated under the conditions.
As shown in
FIG. 7
, in ordinary fluorescent lamps generally used outdoors, flickers with a frequency of 100 Hz, namely discharge of a {fraction (1/100)} second cycle is repeated with a 50 Hz AD voltage. In contrast, in a television camera executing scanning at a rate of 60 fields per second, {fraction (1/60)} second is required for scanning one field. For this reason, both a time required for executing discharge 5 times in a fluorescent lamp and a time required for 3 times of field scanning in a television camera executing scanning a rate of 60 fields per second are {fraction (1/20)} sec, and under this time interval, discharge timing in the fluorescent matches timing for scanning pixel positions within one field of the television camera.
Immediately after a discharge voltage is loaded to a fluorescent lamp, the brightness becomes relatively high, so that also a reflected light from an object at the point of time and on has relatively large magnitude, and a large signal can be obtained at a pixel position with a reflected light having large magnitude therefrom detected at the point of time. When this signal is transmitted as an image signal to a television receiver for reproduction of the image, twinkling with a frequency of 20 Hz, namely flickers is felt.
For instance, in
FIG. 7
, under the discharge timings No.
1
, No.
6
, and No.
11
in a fluorescent lamp as well as the scanning times for fields No.
1
, No.
4
, and No.
7
in a television camera, flickers No. a
1
, No. a
2
, and No. a
3
corresponding thereto respectively are generated. Also for other discharge numbers in the fluorescent lamp and other fields each having a different field number in a television camera, flickers for 3 fields numbered as b
1
, b
2
and b
3
; c
1
, c
2
and c
3
; d
1
, d
2
and d
3
; or e
1
, e
2
and e
3
as one cycle respectively is generated.
Also in a case where a digital type of solid image pick-up device such as a CCD (Charge Coupled Device) is used as a television camera, as a shuttering speed of a shutter for making pixels arrayed two-dimensionally receive a reflected light from an object is equivalent to a field scanning frequency in an analog type of image pick-up tube, if the shuttering speed is 60 Hz or 60 times per second, the flickers described above is generated.
So there has been proposed an image pick-up device capable of suppressing flickers in a fluorescent lamp for suppressing the flickers as described above.
FIG. 8
is a block diagram showing general configuration of an image pick-up device capable of suppressing flickers in a fluorescent lamp based on the conventional technology.
In.
FIG. 8
, a brightness signal outputted from an image pick-up element
101
is inputted into a gain control unit
102
, and a level of the inputted brightness signal is adjusted therein. The brightness signal is transmitted via the gain control unit
102
to an A/D converter
103
to convert the signal to a digital signal, and the converted signal is subjected to appropriate signal processing in a digital image signal processing unit
104
. The digital brightness signal having been subjected to digitalizing processing in the image signal processing unit
104
is transmitted to the D/A converter
105
and is converted to an analog signal therein, and is displayed as an image in an output device
106
.
The digital brightness signal having been subjected to the digitalizing processing in the image signal processing unit
104
is also transmitted to an integrator
107
. In the integrator
107
, an integrated value digital data signal for one field is generated by adding thereto each of the digital brightness signals sequentially transmitted as described above. The generated integrated value digital data signal is transmitted to a gain computing unit
108
. In the gain computing unit
108
, a gain is computed by dividing a reference value by an integrated value indicated by the integrated value digital data signal.
Herein the integrated value digital data signal is a signal including an excessive brightness signal generated due to flickers, and by computing a gain with the gain computing unit
108
, correction of an integrated value digital data signal not including a reference value, namely flickers becomes possible. The computed gain is transmitted as a gain signal to a one-field delay unit
109
, and is inputted into the gain control unit
102
after passage of one field scanning time. In the gain control unit
102
, a level of a brightness signal inputted from the image pick-up element
101
according to a gain signal, and then the processing described above is repeated.
A timing chart for the processing above is shown in FIG.
9
. In
FIG. 9
, each of the brightness signals from start to end of scanning for the n-th field is added in the integrator
107
for obtaining an integrated value for the n-th field. Then each of brightness signals from start to end of scanning for the n+1-th field is also added in the integrator
107
to obtain an integrated value for the n+1-th field. In this step, the integrated value for the n+1-th field is inputted into the gain computing unit
108
at the same timing to obtain a gain for the n-th field.
Further, each of brightness signals from start to end of scanning for the n+2-th field is added in the integrator
107
to obtain an i
Fujitsu Limited
Garber Wendy R.
Staas & Halsey , LLP
Ye Lin
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