EP1091571A2
Expired / Lapsed
EP
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Apparatus and methods for detection and compensation of illumination flicker, detection and measurement of AC line frequency
Assignee: Panasonic Corp
•
Filing: 2000-10-06
•
Granted: —
•
Expires: 2020-10-06
Abstract
Abstract A video signal including illumination flicker component is integrated at each of unit areas (horizontal lines) in a frame (field) of the video signal. The integrated level at each of the unit areas at the frame and the integrated level at the corresponding unit area of an adjacent frame are averaged. Dividing is effected between results of the averaging and integrating every unit area. It is judged whether flicker exists in the video signal by frequency-analyzing results of the dividing result at the unit areas. The unit area may be plural adjacent lines where flickering are negligible. The averaging circuit may be circulation type of or FIR filter. Threshold level for judging the flicker is changed according to a shutter speed control signal. Flicker compensation may be executed by controlling shutter speed or the AGC according to flicker judging result. A still condition at a block in a frame may be detected from the integration result at plural frames. When the block is judged to be still, the flicker is judged. An ac line frequency detection is also disclosed to detect the frequency of the ac line from a video signal generated under illumination including flicker. An imaging circuit may be provided to generate the video signal therein.
Inventors
- 👤 Misa Kasahara
- 👤 Kenji Tabei
- 👤 Makoto Sube
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 11:43
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/70; H04N23/745
Claims Analysis
Total Claims: 47
Claim 1
Independent Claim
111 words
An illumination flicker detection apparatus comprising: integrating means for integrating levels of a video signal at
pixels at each of unit areas included in a frame or field of said video
signal; averaging means for averaging said integrated level at each of
said unit areas at said frame or field and said integrated level at the
corresponding unit area at an adjacent previous frame or field; dividing means for effecting division between results of said
averaging and integrating means every unit area; and flicker judging means for judging whether flicker exists in
said video signal by frequency-analyzing results of said dividing
means at said unit areas and outputting a judging result.
Claim 2
Dependent Claim
19 words
A n illumination flicker detection apparatus as claimed in claim
1, wherein said unit area is a horizontal line.
Claim 3
Dependent Claim
32 words
An illumination flicker detection apparatus as claimed in claim 1,
wherein said unit area is a plurality of adjacent horizontal lines
where variation in said levels due to said flicker is negligible.
Claim 4
Dependent Claim
41 words
An illumination flicker detection apparatus as claimed in claim 1,
wherein each of said unit areas includes a plurality of horizontal
lines with interval at a frame, said horizontal lines showing the same
phase in flicker component in said video signal.
Claim 5
Dependent Claim
20 words
An illumination flicker detection apparatus as claimed in claim 1,
wherein said averaging means comprising a circulation type of filter.
Claim 6
Dependent Claim
20 words
An illumination flicker detection apparatus as claimed in claim 1,
wherein said averaging means comprising a Finite Impulse Response
filter.
Claim 7
Dependent Claim
133 words
An illumination flicker detection apparatus as claimed in claim 1,
further comprising: first summing means for summing said result of said
integrating means at said frame or field and said result of said
integrating means at another frame or field at every said unit area;
and second summing means for summing said results of said
averaging means at said frame or field and said result of said
averaging means at said another frame or field at every unit area,
wherein said another frame or field is prior to said frame or field by
a predetermined number of frames or fields which is determined by a
frequency of said flicker and a frame frequency of said video signal
and said dividing means effects said division between said results of
first and second summing means.
Claim 8
Dependent Claim
84 words
An illumination flicker detection apparatus as claimed in claim 1,
further comprising: first summing means for summing said results of said
integrating means of a predetermined number of adjacent frames or
fields at every unit area, said adjacent frames or fields including said
frame or field; and second summing means for summing said results of said
averaging means of said adjacent frames or fields at every unit area,
wherein said dividing means effects said division between said
results of first and second summing means.
Claim 9
Dependent Claim
66 words
An illumination flicker detection apparatus as claimed in claim 1,
further comprising another averaging means for averaging said
results of said dividing means at a plurality of said unit areas at said
frame or field, wherein each of said unit areas includes a plurality of
horizontal lines with interval at a frame, said horizontal lines
showing the same phase in flicker component in said video signal.
Claim 10
Dependent Claim
55 words
An illumination flicker detection apparatus as claimed in claim
1, further comprising threshold level generating means for
generating a threshold level in accordance with a shutter speed
control signal which is used for generating said video signal,
wherein said flicker judging means judges whether said flicker exists
in said video signal using said threshold level.
Claim 11
Dependent Claim
151 words
An illumination flicker compensation signal generation
apparatus comprising: integrating means for integrating levels of a video signal at
pixels at each of unit areas included in a frame or field of said video
signal; averaging means for averaging said integrated level at each of
said unit areas at said frame or field and said integrated level at the
corresponding unit area at an adjacent frame or field; dividing means for effecting division between results of said
averaging and integrating means every unit area; flicker judging means for judging whether flicker exists in
said video signal by frequency-analyzing results of said dividing
means at said unit areas and outputting a judging result; and flicker compensation means for generating a shutter speed
control signal and an automatic gain controlling signal for
generating said video signal in accordance with said judging result
of said flicker judging means to compensate flicker in said video
signal.
Claim 12
Independent Claim
110 words
A method of detecting flicker in a video signal comprising the
steps of: (a) integrating video levels of a video signal at pixels at each
of unit areas included in a frame or field of said video signal; (b) averaging said integrated level at each of said unit areas
at said frame or field and said integrated level at the corresponding
unit areas at an adjacent frame or field; (c) effecting division between results of said steps of (a) and
(b) every unit area; and (d) judging whether flicker exists in said video signal by
frequency-analyzing results of said step (c) at said unit areas and
outputting a judging result.
Claim 13
Dependent Claim
15 words
A method as claimed in claim 12, wherein said unit area is a
horizontal line.
Claim 14
Dependent Claim
30 words
A method as claimed in claim 12, wherein said unit area is a
plurality of adjacent horizontal lines where variation of said video
levels due to said flickering is negligible.
Claim 15
Dependent Claim
38 words
A method as claimed in claim 12, wherein each of said unit
areas includes a plurality of horizontal lines with interval at a frame,
said horizontal lines showing the same phase in flicker component in
said video signal.
Claim 16
Dependent Claim
28 words
A method as claimed in claim 12, wherein said step (b)
comprises step of: circulating said integrated level every frame or field with a
coefficient less than one.
Claim 17
Dependent Claim
19 words
A method as claimed in claim 12, wherein said step (b)
comprises the steps of: Finite-Impulse-Response-filtering said integrated level.
Claim 18
Dependent Claim
123 words
A method as claimed in claim 12, further comprising: (e) summing said result of said step (a) at said frame or field
and said result of said step (a) at another frame or field at every said
unit area; and (f) summing said results of said averaging step at said frame
or field and said result of said step (b) at another frame or field at
every unit area, wherein said another frame or field is prior to said
frame or field by a predetermined number of frames or fields which
is determined by a frequency of said flicker and a frame frequency of
said video signal and said dividing means effects said division
between said results of said steps (e) and (f).
Claim 19
Dependent Claim
73 words
A method as claimed in claim 12, further comprising: (e) summing said results of said step (a) of a predetermined
number of adjacent frames or fields at every unit area, said adjacent
frames or fields including said frame or field; and (f) summing said results of said step (b) of said adjacent
frames or fields at every unit area, wherein said division is effected
between said results of said step (e) and (f).
Claim 20
Dependent Claim
62 words
A method as claimed in claim 12, further comprising the step of
averaging said results of said step (c) of a plurality of said unit areas
at said frame or field, wherein each of said unit areas includes a
plurality of horizontal lines with interval at a frame, said horizontal
lines showing the same phase in flicker component in said video
signal.
Claim 21
Dependent Claim
48 words
A method as claimed in claim 12, further comprising the steps
of: generating a threshold level in accordance with a shutter
speed control signal which is used for generating said video signal,
wherein it is judged whether said flicker exists in said video signal
using said threshold level.
Claim 22
Independent Claim
140 words
A method of compensating flicker in a video signal comprising
the steps of: (a) integrating video levels of a video signal at pixels at each
of unit areas included in a frame or field of said video signal; (b) averaging said integrated level at each of said unit areas
at said frame or field and said integrated level at the corresponding
unit areas at an adjacent frame or field; (c) effecting division between results of said steps of (a) and
(b) every unit area; and (d) judging whether flicker exists in said video signal by
frequency-analyzing results of said step (c) at unit areas and
outputting a judging result; and (e) generating a shutter speed control signal and an
automatic gain controlling signal in accordance with said judging
result of said step (d) to compensate flicker in said video signal.
Claim 23
Dependent Claim
139 words
An illumination flicker detection apparatus comprising: integrating means for integrating levels of a video signal at
pixels at each of unit areas included in a frame or field of said video
signal; averaging means for averaging said integrated level at each of
said unit areas at said frame or field and said integrated level at the
corresponding unit area at an adjacent frame or field; still portion judging means for judging whether image at
every block including a portion of said unit areas at a frame is still in
accordance with result of said integrating means; dividing means for effecting division between results of said
averaging and integrating means every unit area; and flicker judging means for judging whether flicker exists in
said video signal in accordance with results of said dividing means
and said still portion judging means.
Claim 24
Dependent Claim
18 words
An illumination flicker detection apparatus as claimed in claim
23, wherein said unit area is a horizontal line.
Claim 25
Dependent Claim
33 words
An illumination flicker detection apparatus as claimed in claim
23, wherein said unit area is a plurality of adjacent horizontal lines
where variation of said video levels due to said flickering is
negligible.
Claim 26
Dependent Claim
153 words
An illumination flicker detection apparatus as claimed in claim
23, wherein said blocks are arranged in the vertical direction at a
frame or a field, a vertical length of each block is determined in
accordance with an integer times one cycle of illumination variation
due to an ac line voltage, used for generating said video signal and a
frame frequency of said video signal, and said still portion judging
means comprises: summing means for summing integration results of unit areas
at every said block; variation detection means for detecting variation in result of
said summing means between each of said blocks of the present
frame or field and the corresponding block of a previous frame or
field; and comparing means for comparing said variation with a
threshold value, wherein said still portion judging means judges that
image at each of said blocks is still when said variation is lower than
said threshold value.
Claim 27
Dependent Claim
116 words
An illumination flicker detection apparatus as claimed in claim
26, wherein said variation detection means comprises: difference calculation means for calculating a difference in
results of said summing means between each of said blocks of the
present frame or field and the corresponding block of a previous
frame or field; dividing means for dividing result of said difference
calculating means by said result of said summing means of said
present frame or field; and comparing means for comparing result of said dividing means
with a threshold value, wherein said still portion judging means
judges that image at each of said blocks is still when said result of
said dividing means is lower than said threshold value.
Claim 28
Dependent Claim
126 words
An illumination flicker detection apparatus as claimed in claim
26, wherein said variation detection means comprises: variation detection averaging means for averaging results of
said summing means between present and previous frames or fields
at each of said blocks; difference calculation means for calculating a difference in
result of said summing means and said result of said variation
detection averaging means; dividing means for dividing result of said difference
calculating means by said result of said summing means of said
present frame or field; and comparing means for comparing result of said dividing means
with a threshold value, wherein said still portion judging means
judges that image at every block areas is still when said result of said
dividing means is lower than said threshold value.
Claim 29
Dependent Claim
184 words
An illumination flicker compensation signal generation
apparatus comprising: integrating means for integrating levels of a video signal at
pixels at each of unit areas included in a frame or field of said video
signal; averaging means for averaging said integrated level at each of
said unit areas at said frame or field and said integrated level at the
corresponding unit area of at least an adjacent frame or field; still portion judging means for judging whether image at
every block including a portion of said unit areas at a frame is still in
accordance with result of said integrating means; dividing means for effecting division between results of said
averaging and integrating means every unit area; and flicker judging means for judging whether flicker exists in
said video signal in accordance with results of said dividing means
and said still portion judging means ; and flicker compensation means for generating a shutter speed
control signal and an automatic gain controlling signal for
generating said video signal in accordance with said judging result
of said flicker judging means to compensate flicker in said video
signal.
Claim 30
Independent Claim
127 words
A method of compensating flicker in a video signal comprising
the steps of: (a) integrating levels of a video signal at pixels at each of unit
areas included in a frame or field of said video signal; (b) averaging said integrated level at each of said unit areas at
said frame or field and said integrated level at the corresponding
unit area at an adjacent frame or field; (c) judging whether image at every block including a portion
of said unit areas is still in accordance with result of said step (a); (d) effecting division between results of said steps of (a) and
(b) every unit area; and (e) judging whether flicker exists in said video signal in
accordance with results of said steps (c) and (d).
Claim 31
Dependent Claim
15 words
A method as claimed in claim 30, wherein said unit area is a
horizontal line.
Claim 32
Dependent Claim
30 words
A method as claimed in claim 30, wherein said unit area is a
plurality of adjacent horizontal lines where variation of said video
levels due to said flickering is negligible.
Claim 33
Dependent Claim
141 words
An illumination flicker detection apparatus as claimed in claim
30, wherein said blocks are arranged in the vertical direction at a
frame or a field, a vertical length of each block is determined in
accordance with an integer times one cycle of illumination variation
due to an ac line voltage, used for generating said video signal, and
said step (c) comprises the steps of: (f) summing integration results of unit areas at every said
block; (g) detecting variation in result of said step of (f) between
each of said blocks of the present frame or field and the
corresponding block of a previous frame or field; and (h) comparing said variation with a threshold value, wherein in said step (c), it is judged that image at each of said blocks
is still when said variation is lower than said threshold value.
Claim 34
Dependent Claim
112 words
An illumination flicker detection apparatus as claimed in claim
33, wherein said step (g) includes the steps of: (i) calculating a difference in results of said step of (f)
between each of said blocks of the present frame or field and the
corresponding block of a previous frame or field; (j) dividing result of said step (i) by said result of said step
(f) of said present frame or field; and (k) comparing result of said step (j) with a threshold value, wherein in said step (c) it is judged that image at each of said blocks
is still when said result of said step (j) is lower than said threshold
value.
Claim 35
Dependent Claim
114 words
A method as claimed in claim 33, wherein said step (g) includes
the steps of: (i) averaging results of said step of (f) between present and
previous frames or fields at each of said blocks; (j) calculating a difference in result of said step of (f) and said
result of said step (b); (k) dividing result of said step (j) by said result of said step (f)
of said present frame or field; and (l) comparing result of said step (k) with a threshold value, wherein in said step (c), it is judged that image at every block areas
is still when said result of said step (k) is lower than said threshold
value.
Claim 36
Independent Claim
163 words
A method of compensating flicker in a video signal comprising
the steps of: (a) integrating levels of a video signal at pixels at each of unit
areas included in a frame or field of said video signal; (b) averaging said integrated level at each of said unit areas at
said frame or field and said integrated level at the corresponding
unit area at an adjacent frame or field; (c) judging whether image at every block including a portion
of said unit areas is still in accordance with result of said step (a); (d) effecting division between results of said steps of (a) and
(b) every unit area; and (e) judging whether flicker exists in said video signal in
accordance with results of said steps (c) and (d); and (f) generating a shutter speed control signal and an automatic
gain controlling signal for generating said video signal in accordance
with said judging result of said step (e) to compensate flicker in said
video signal.
Claim 37
Dependent Claim
56 words
An ac line frequency detection apparatus comprising: flicker component detection means for detecting a flicker
component in a video signal generated with illumination of which
luminance varies with ac line voltage; and flicker judging means for judging whether flicker exists in
said video signal in accordance with said detected flicker component
and outputting the judging result.
Claim 38
Dependent Claim
99 words
An ac line frequency detection apparatus as claimed in claim 37,
wherein said flicker component detection means comprises: integrating means for integrating levels of said video signal at
pixels at each of unit areas included in a frame or field of said video
signal; averaging means for averaging said integrated level at each of
said unit areas at said frame or field and said integrated level at the
corresponding unit area at an adjacent frame or field; dividing means for effecting division between results of said
averaging and integrating means every unit area to output said
detected flicker component.
Claim 39
Dependent Claim
33 words
An ac line frequency detection apparatus as claimed in claim 37,
wherein said flicker judging means comprises: variation analyzing means for analyzing variation of said
detected flicker component with respect to horizontal lines.
Claim 40
Dependent Claim
27 words
An ac line frequency detection apparatus as claimed in claim 37,
wherein said flicker judging means comprises: spectrum analyzing
means for analyzing spectrum of said flicker component.
Claim 41
Dependent Claim
19 words
An ac line frequency detection apparatus as claimed in claim 37,
wherein said unit area is a horizontal line.
Claim 42
Dependent Claim
55 words
An ac line frequency measuring apparatus comprising: imaging means for generating a video signal with
illumination of which luminance varies with ac line voltage; flicker component detection means for detecting a flicker
component in said video signal; and frequency detection means for detecting a frequency of said
flicker component from said flicker component detection means.
Claim 43
Independent Claim
49 words
A method of measuring an ac line frequency comprising the
steps of: (a) detecting a flicker component in a video signal generated
with illumination of which luminance varies with ac line voltage;
and (b) judging whether flicker exists in said video signal in
accordance with said detected flicker component.
Claim 44
Dependent Claim
87 words
A method as claimed in claim 43, wherein said step (a)
comprising steps of: integrating levels of said video signal at pixels at each of unit
areas included in a frame or field of said video signal; averaging said integrated level at each of said unit areas at
said frame or field and said integrated level at the corresponding
unit area of at an adjacent frame or field; effecting division between results of said averaging and
integrating steps every unit area to output said detected flicker
component.
Claim 45
Dependent Claim
26 words
A method as claimed in claim 43, wherein said step (b)
comprising steps of: analyzing variation of said detected flicker component with
respect to horizontal lines.
Claim 46
Dependent Claim
20 words
A method as claimed in claim 43, wherein said step (b)
comprising steps of: analyzing spectrum of said flicker component.
Claim 47
Dependent Claim
15 words
A method as claimed in claim 43, wherein said unit area is a
horizontal line.
References Cited (Backward Citations)
US5384595A
Cited
EP0762742A2
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