# US 5,347,320 A · Circuit for preventing automatic white balance error operation

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- Number: US 5,347,320 A
- Document ID: US5347320A
- Status: Granted
- Kind: A
- Application number: 07/963,547
- Filed: 1992-10-20
- Granted: 1994-09-13
- Earliest claimed: 1991-11-30
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Jong-Gyun Lim
- Web page: https://patentgrep.com/patent/US5347320A

## CPC

- H04N 23/88: for colour balance, e.g. white-balance circuits or colour temperature control
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An error operation in a white balance circuit is prevented from occurring. This error operation occurs when a white balance control is mistakenly executed upon recognizing that a color temperature of the environment is changed during a counter light correction either when an iris is adjusted or when an amplifying gain in an amplifying stage is controlled. The counter light correcting function is executed in order to account for the fact that an object appears shaded in the vicinity of a bright background. The error operation is prevented by maintaining the white balance correction at a present state when a voltage from a counter light correction circuit becomes greater than a reference voltage.

## Claims

### Claim 1

In a camera provided with an automatic white balance circuit, an automatic white balance circuit error operation preventing circuit comprising:
counter light correcting means for executing a counter light correction,
comparing means for outputting a control signal for maintaining a present white balance state when a counter light correcting voltage outputted from said counter light correcting means is greater than a reference value; and
maintaining means for maintaining a present white balance correcting state when the control signal is outputted by the comparing means and outputting a white balance corrected video signal.

### Claim 2 (depends on 1)

An automatic white balance circuit error operation preventing circuit as defined in claim 1, wherein said counter light correcting means comprises a counter light correcting section for outputting the counter light correcting voltage, and an iris adjusting section for outputting a second control signal for adjusting an opening state of an iris in accordance with the counter light correcting voltage outputted from said counter light correcting voltage section.

### Claim 3 (depends on 1)

An automatic white balance error operation preventing circuit as defined in claim 1, wherein said counter light correcting means comprises a variable resistor for adjusting an amplifying gain of an amplifier.