US4736241A
Expired / Lapsed
US
⏱️ 0.0 years remaining
White balance adjusting device of color video camera
Assignee: Hitachi Ltd
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Filing: 1986-12-03
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Granted: 1988-04-05
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Expires: 2006-12-03
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 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 has a circuit for generating a color temperature change detection signal from at least two different chrominance signals, a comparator/amplifier 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
US
Data Source
google_patents
Last Synchronized
2026-10-29 00:34
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
133 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 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 are supplied and a gain of which is controlled by a control signal; detection means for detecting a change of a color temperature from at least two different chrominance signals and providing a corresponding output signal; and compare/amplify means for comparing the output signal of said detection means with a distinct reference voltage source to generate the control signal to be fed back to said variable gain amplifiers.
Claim 2
Dependent Claim
133 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 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 are supplied and a gain of which is controlled by a control signal; detection means for detecting a change of a color temperature from at least two different chrominance signals and providing a corresponding output signal; and compare/amplify means for comparing the output signal of said detection means with a distinct reference voltage source 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 1 wherein said detection means includes means for processing the red (R) signal and blue (B) signal and filtering (averaging) the processed signals to generate a detection signal representative of color temperature change.
Claim 4
Dependent Claim
59 words
A white balance adjusting device for a color video camera according to claim 2 wherein said detection means includes logarithmic compression circuits to which the red (R) signal and blue (B) signal are supplied, respectively, a processing circuit for subtracting the outputs of said logarithmic compression circuits, and a filter circuit for filtering the output of said processing circuit.
Claim 5
Dependent Claim
96 words
A white balance adjusting device for a color video camera according to claim 2, wherein said compare/amplify means for providing said feedback control signal includes a comparator/amplifier having two inputs, one of which is for applying said reference voltage source and the other is to apply thereto the detection signal representative of color temperature change generated at the output of said detection means wherein said comparator/amplifier has a non-linear amplification characteristic with respect to an input compare level, and has an amplification factor to effect in a negative feedback loop gain of less than 20 db.
Claim 6
Dependent Claim
77 words
A white balance adjusting device for a color video camera according to claim 2, wherein said variable gain amplifiers include two variable gain amplifiers and wherein there is further included a tracking correction circuit for converting the feedback control signal from said compare/amplifying means to two central signals to be supplied to said two variable gain amplifiers and wherein said two control signals change on different loci of change in accordance with a change of color temperature.
Claim 7
Dependent Claim
117 words
A white balance adjusting device for a color video camera according to claim 2, further including level compare means for comparing the output of said detection means with the reference voltage source to generate a high level or low level feedback control signal depending on the comparison result, count means for counting up or down clock pulses in accordance with the level of the control signal outputted by said level compare means, digital/analog conversion means for converting the count of said count means to an analog signal, control means 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 8
Dependent Claim
45 words
A white balance adjusting device for a color video camera according to claim 1 wherein said detection means includes means for filtering (averaging) the red (R) and blue (B) signals and processing the filtered signals to generate a detection signal representative of color temperature change.
Claim 9
Dependent Claim
50 words
A white balance adjusting device for a color video camera according to claim 7, wherein said detection means further includes respective logarithmic compression circuits for logarithmically compressing the filtered R signal and B signal and then processing the filtered signals to generate a detection signal representative of color temperature change.
Claim 10
Dependent Claim
96 words
A white balance adjusting device for a color video camera according to claim 7, wherein said compare/amplify means for providing said feedback control signal includes a comparator/amplifier having two inputs, one of which is for applying said reference voltage source and the other is to apply thereto the detection signal representative of color temperature change generated at the output of said detection means, wherein said comparator/amplifier has a non-linear amplification characteristic with respect to an input compare level, and has an amplification factor to effect in a negative feedback loop gain of less than 20 db.
Claim 11
Dependent Claim
117 words
A white balance adjusting device for a color video camera according to claim 7, further including level compare means for comparing the output of said detection means with the reference voltage source to generate a high level or low level feedback control signal depending on the comparison result, count means for counting up or down clock pulses in accordance with the level of the control signal outputted by said level compare means, digital/analog conversion means for converting the count of said count means to an analog signal, control means 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 12
Dependent Claim
50 words
A white balance adjusting device for a color video camera according to claim 10, further comprising amplifiers for setting the white balance under illumination by the reference color temperature and being interposed on the input side of said variable gain amplifiers and on respective R signal and B signal paths.
Claim 13
Dependent Claim
42 words
A white balance adjusting device for a color video camera according to claim 1 wherein said detection means includes means for processing two different differential chrominance signals and filtering (averaging) the processed signals to generate a detection signal representative of color temperature.
Claim 14
Dependent Claim
96 words
A white balance adjusting device for a color video camera according to claim 12, wherein said compare/amplify means for providing said feedback control signal includes a comparator/amplifier having two inputs, one of which is for applying said reference voltage source and the other is to apply thereto the detection signal representative of color temperature change generated at the output of said detection means, wherein said comparator/amplifier has a non-linear amplification characteristic with respect to an input compare level, and has an amplification factor to effect in a negative feedback loop gain of less than 20 db.
Claim 15
Dependent Claim
77 words
A white balance adjusting device for a color video camera according to claim 12, wherein said variable gain amplifiers include two variable gain amplifiers and wherein there is further included a tracking correction circuit for converting the feedback control signal from said compare/amplifying means to two central signals to be supplied to said two variable gain amplifiers and wherein said two control signals change on different loci of change in accordance with a change of color temperature.
Claim 16
Dependent Claim
42 words
A white balance adjusting device for a color video camera according to claim 1 wherein said detection means includes means for filtering (averaging) two different differential chrominance signals and processing the filtered signals to generate a detection signal representative of color temperature.
Claim 17
Dependent Claim
59 words
A white balance adjusting device for a color video camera according to claim 1 wherein said detection means includes logarithmic compression circuits to which the red (R) signal and blue (B) signal are applied, respectively, a processing circuit for subtracting the outputs of said logarithmic compression circuits, and a filter circuit for filtering the output of said processing circuit.
Claim 18
Dependent Claim
63 words
A white balance adjusting device for a color video camera according to claim 1 wherein said detection means includes filter circuits for filtering the red (R) signal and blue (B) signal, logarithmic compression circuit for logarithmically compressing the filtered signals, and a processing circuit for subtracting the outputs of said logarithmic compression circuits to generate a detection signal representative of color temperature change.
Claim 19
Dependent Claim
96 words
A white balance adjusting device for a color video camera according to claim 1 wherein said compare/amplify means for providing said feedback control signal includes a comparator/amplifier having two inputs, one of which is for applying said reference voltage source and the other is to apply thereto the detection signal representative of color temperature change generated at the output of said detection means, wherein said comparator/amplifier has a non-linear amplification characteristic with respect to an input compare level, and has an amplification factor to effect in a negative feedback loop gain of less than 20 db.
Claim 20
Dependent Claim
77 words
A white balance adjusting device for a color video camera according to claim 1, wherein said variable gain amplifiers include two variable gain amplifiers and wherein there is further included a tracking correction circuit for converting the feedback control signal from said compare/amplifying means to two central signals to be supplied to said two variable gain amplifiers and wherein said two control signals change on different loci of change in accordance with a change of color temperature.
Claim 21
Dependent Claim
117 words
A white balance adjusting device for a color video camera according to claim 1, further including level compare means for comparing the output of said detection means with the reference voltage source to generate a high level or low level feedback control signal depending on the comparison result, count means for counting up or down clock pulses in accordance with the level of the control signal outputted by said level compare means, digital/analog conversion means for converting the count of said count means to an analog signal, control means 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.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-04-05 | 1991-10-05 | 1992-04-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-05 | 1995-10-05 | 1996-04-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-05 | 1999-10-05 | 2000-04-05 | $7700.00 | Window Closed / Lapsed |