EP0224904A2
Expired / Lapsed
EP
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White balance adjusting device of color video camera
Assignee: Hitachi Ltd
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Filing: 1986-12-02
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Granted: —
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Expires: 2006-12-02
Abstract
Abstract A white balance adjusting device detects a change of color temperature for an illuminating light source from chrominance signals supplied from an image pickup device (l) of a color video camera and controls gains of circuits of a chrominance signal processing circuit for processing red (R) signal and blue (B) signal in accordance with the detected signal to automatically adjust the white balance. The device comprises a circuit (l0, l0′, ll, lll - ll4) for generating a color temperature change detection signal from at least two different chrominance signals, a comparator/amplifier (l2, l4, l2′, l9, 20, 2l) for amplifying a difference between the detection signal and a reference voltage, a tracking correction circuit to which the output of the comparator/amplifier is supplied and which produces two control signals, and gain control circuits for controlling gains for the red (R) signal and blue (B) signal in accordance with the two control signals. The color temperature change detection circuit, comparator/amplifier, tracking correction circuit and gain control circuits constitute a negative feedback loop.
Inventors
- 👤 Toshio Murakami
- 👤 Yasushi Takagi
- 👤 Hiroyasu Ohtsubo
- 👤 Yutaka Satoh
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 11:09
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/57; H04N23/00; H04N23/80; H04N23/84; H04N23/88; H04N9/00; H04N9/64; H04N9/73
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
134 words
A white balance adjusting device for a color video camera for automatically white-balancing by controlling a chrominance signal processing circuit by a white balance control signal derived from chrominance signals supplied from an image pickup device, comprising: variable gain amplifiers (3, 4) to which at least red (R) and blue (B) signals of the chrominance signals generated by processing the output signals of said image pickup device (l) are supplied and a gain of which is controlled by a control signal; detection means (l0, l0′, ll, lll - ll4) for detecting a change of a color temperature from at least two different chrominance signals; and compare/amplify means for comparing the output signal of said detection means with a reference voltage to generate the control signal to be fed back to said variable gain amplifiers.
Claim 2
Dependent Claim
134 words
A white balance adjusting device for a color video camera for automatically white-balancing by controlling a chrominance signal processing circuit by a white balance control signal derived from chrominance signals supplied from an image pickup device, comprising: variable gain amplifiers (3, 4) to which at least red (R) and blue (B) signals of the chrominance signals generated by processing the output signals of said image pickup device (l) are supplied and a gain of which is controlled by a control signal; detection means (l0, l0′, ll, lll - ll4) for detecting a change of a color temperature from at least two different chrominance signals; and compare/amplify means for comparing the output signal of said detection means with a reference voltage to generate the control signal to be fed back to said variable gain amplifiers.
Claim 3
Dependent Claim
46 words
A white balance adjusting device for a color video camera according to Claim l wherein said detection means includes means (l0, ll) for processing the red (R) signal and blue (B) signal and filtering (averaging) the processed signals to generate a color temperature change detection signal.
Claim 4
Dependent Claim
46 words
A white balance adjusting device for a color video camera according to Claim l wherein said detection means includes means (l0, lll, ll2) for filtering (averaging) the red (R) and blue (B) signals and processing the filtered signals to generate a color temperature change detection signal.
Claim 5
Dependent Claim
43 words
A white balance adjusting device for a color video camera according to Claim l wherein said detection means includes means (l0, ll) for processing two different differential chrominance signals and filtering (averaging) the processed signals to generate a color temperature change detection signal.
Claim 6
Dependent Claim
44 words
A white balance adjusting device for a color video camera according to Claim l wherein said detection means includes means (ll3, ll4, l0) for filtering (averaging) two different differential chrominance signals and processing the filtered signals to generate a color temperature change detection signal.
Claim 7
Dependent Claim
63 words
A white balance adjusting device for a color video camera according to Claim l wherein said detection means includes logarithmic compression circuits (l7r, l7b) to which the red (R) signal and blue (B) signal are applied, respectively, a processing circuit (l8) for subtracting the outputs of said logarithmic compression circuits, and a filter circuit (ll) for filtering the output of said processing circuit.
Claim 8
Dependent Claim
63 words
A white balance adjusting device for a color video camera according to Claim 2 wherein said detection means includes logarithmic compression circuits (l7r, l7b) to which the red (R) signal and blue (B) signal are supplied, respectively, a processing circuit (l8) for subtracting the outputs of said logarithmic compression circuits, and a filter circuit (ll) for filtering the output of said processing circuit.
Claim 9
Dependent Claim
66 words
A white balance adjusting device for a color video camera according to Claim l wherein said detection means includes filter circuits (lll, ll2) for filtering the red (R) signal and blue (B) signal, logarithmic compression circuit (l7r, l7b) for logarithmically compressing the filtered signals, and a processing circuit (l8) for subtracting the outputs of said logarithmic compression circuits to generate a color temperature change detection circuit.
Claim 10
Dependent Claim
35 words
A white balance adjusting device for a color video camera according to Claim 3 wherein said detection means further includes logarithmic compression circuits (l7r, l7b) for logarithmically compressing the filtered R signal and B signal.
Claim 11
Dependent Claim
85 words
l0. A white balance adjusting device for a color video camera according to Claim l wherein said feedback means includes a comparator/amplifier (l2, l2′) which has the reference voltage applied to one input thereof and the color temperature change detection signal at the output of said detection means applied to the other input thereof, has a non-linear amplification characteristic to an input compare level, and has an amplification factor to render a loop gain of the negative feedback loop to be less than 20 dB.
Claim 12
Dependent Claim
84 words
A white balance adjusting device for a color video camera according to Claim 2 wherein said feedback means includes a comparator/amplifier (l2, l2′) which has the reference voltage applied to one input thereof and the color temperature change detection signal at the output of said detection means applied to the other input thereof, has a non-linear amplification characteristic to an input compare level, and has an amplification factor to render a loop gain of the negative feedback loop to be less than 20 dB.
Claim 13
Dependent Claim
84 words
A white balance adjusting device for a color video camera according to Claim 3 wherein said feedback means includes a comparator/amplifier (l2, l2′) which has the reference voltage applied to one input thereof and the color temperature change detection signal at the output of said detection means applied to the other input thereof, has a non-linear amplification characteristic to an input compare level, and has an amplification factor to render a loop gain of the negative feedback loop to be less than 20 dB.
Claim 14
Dependent Claim
84 words
A white balance adjusting device for a color video camera according to Claim 4 wherein said feedback means includes a comparator/amplifier (l2, l2′) which has the reference voltage applied to one input thereof and the color temperature change detection signal at the output of said detection means applied to the other input thereof, has a non-linear amplification characteristic to an input compare level, and has an amplification factor to render a loop gain of the negative feedback loop to be less than 20 dB.
Claim 15
Dependent Claim
68 words
A white balance adjusting device for a color video camera according to Claim l wherein said feedback means further includes a tracking correction circuit (l4) for converting the control signal to be supplied to said two variable gain amplifiers to two control signals which change on different loci of change in accordance with a change of color temperature and supplying the controlled signals to said variable gain amplifiers.
Claim 16
Dependent Claim
68 words
A white balance adjusting device for a color video camera according to Claim 2 wherein said feedback means further includes a tracking correction circuit (l4) for converting the control signal to be supplied to said two variable gain amplifiers to two control signals which change on different loci of change in accordance with a change of color temperature and supplying the controlled signals to said variable gain amplifiers.
Claim 17
Dependent Claim
68 words
A white balance adjusting device for a color video camera according to Claim 4 wherein said feedback means further includes a tracking correction circuit (l4) for converting the control signal to be supplied to said two variable gain amplifiers to two control signals which change on different loci of change in accordance with a change of color temperature and supplying the controlled signals to said variable gain amplifiers.
Claim 18
Dependent Claim
117 words
A white balance adjusting device for a color video camera according to Claim l wherein said feedback means includes level compare means (l2′) for comparing the output of said detection means with the reference voltage to generate a high level or low level signal depending on the comparison result, count means (l9, 20) for counting up or down clock pulses in accordance with the output of said level compare means, digital/analog conversion means (2l) for converting the count of said count means to an analog signal, control means (22) for controlling the supply of the clock pulses to said count means, and means for feeding the output of said digital/analog conversion means to said variable gain amplifiers.
Claim 19
Dependent Claim
117 words
A white balance adjusting device for a color video camera according to Claim 2 wherein said feedback means includes level compare means (l2′) for comparing the output of said detection means with the reference voltage to generate a high level or low level signal depending on the comparison result, count means (l9, 20) for counting up or down clock pulses in accordance with the output of said level compare means, digital/analog conversion means (2l) for converting the count of said count means to an analog signal, control means (22) for controlling the supply of the clock pulses to said count means, and means for feeding the output of said digital/analog conversion means to said variable gain amplifiers.
Claim 20
Dependent Claim
117 words
A white balance adjusting device for a color video camera according to Claim 3 wherein said feedback means includes level compare means (l2′) for comparing the output of said detection means with the reference voltage to generate a high level or low level signal depending on the comparison result, count means (l9, 20) for counting up or down clock pulses in accordance with the output of said level compare means, digital/analog conversion means (2l) for converting the count of said count means to an analog signal, control means (22) for controlling the supply of the clock pulses to said count means, and means for feeding the output of said digital/analog conversion means to said variable gain amplifiers.
Claim 21
Dependent Claim
46 words
A white balance adjusting device for a color video camera according to Claim l9 further comprising amplifiers (34, 35) for setting the white balance under illumination by the reference color temperature, in previous stages of said variable gain amplifiers for the R signal and B signal.
References Cited (Backward Citations)
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