JPH01309490A - Automatic white balance system - Google Patents

Abstract

PURPOSE:To easily attain temperature compensation by providing a temperature sensor in common to both a white balance detection circuit and a circuit regulating a level of each chroma signal and regulating the level of each chroma signal based on a preset conversion data in response to the output. CONSTITUTION:A temperature sensor 21 to detect ambient temperature is arranged at a position detecting temperature in common to any of a white balance sensor 1, inverse amplifiers 3, 4 and an image pickup signal processing circuit 18. The output of the temperature sensor 21 is amplified by the inverse amplifier 22, converted into a digital value by an A/D converter 23 and the result is inputted to data curve conversion sections 11, 12 of a microcomputer 8. The conversion data for the conversion sections 11, 12 is provided as a ROM table and the ambient temperature detected by the temperature sensor 21 is inputted to the conversion section 11, 12 to convert the color temperature information R/G, B/G of the white balance sensor 1 in response to the ambient temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an auto white balance system, and more specifically, an auto white balance system that performs white balance adjustment by adjusting each chroma signal level based on the output of a white balance detection circuit. Concerning improvements in temperature compensation in balance systems.

[Prior Art] In a conventional auto white balance system, as shown in FIG.
Information R/G and B/G regarding the color temperature of the three primary colors of B are detected, respectively, and the respective information R/G and B/G are amplified by inverting amplifiers 53 and 54. Inverting amplifier 53 (54
), the resistor 53b is connected to the operational amplifier 53a (54a).

53c (54b, 54c) determines the slope, and resistor 53d (54d) determines the offset voltage. The signals amplified by these inverting amplifiers 53 and 54 are then passed through a low pass filter (hereinafter referred to as LPF).
) 55 and 56 to suppress ripple components included when a fluorescent light or the like is turned on, and further curve converter 57 .
After analog curve conversion is performed in step 58, this signal is used as a white balance control signal, and gain control of the chroma signals R and B is performed in gain control amplifiers 19 and 20 in the imaging signal processing circuit 18. The curve conversion section 57 (58) includes diodes 57a (58a) and a resistor 57b.

57c (58b, 58c) and an electromotive force source 57d (5
8d).

[Invention or problem to be solved] By the way, white balance sensor 1 + inverting amplifier 5
B, 54. The input/output characteristics of the imaging signal processing circuit 18 and the like change depending on the ambient temperature. When the ambient temperature is Ta, for example, when Ta=Tal and when Ta=Ta2 (<
Tag), the output voltage of the white balance sensor 1 changes differently with respect to the color temperature as shown in FIG. The control signal voltage required to adjust and achieve correct white balance adjustment also varies differently, as shown in FIG. Note that, assuming that color temperature is T, the horizontal axis in FIGS. 7 and 8 uses MIRED (106/T). Once, the ambient temperature T
If a changes, the white balance will not be adjusted properly.

Therefore, in order to compensate for such changes in ambient temperature, for example, the resistors 53b, 53c, 53d (54b, 54c,
54 d) It is common practice to use a thermistor. However, in this case, since there are many parameters that change, complicated experiments such as trial and error are required to determine the optimal compensation constant, such as determining the temperature coefficient of the thermistor that should be used.

In view of these problems, an object of the present invention is to provide an auto white balance system that makes it possible to easily perform temperature compensation without the complexity of determining compensation constants, etc. [Means and effects for solving the problem] The present invention The auto white balance system adjusts the white balance by adjusting the level of each chroma signal based on the output value of the white balance detection circuit. A common temperature sensor is provided for both to detect the temperature related to the circuit for adjusting the signal level, and according to the output of this temperature sensor, the conversion data set in advance in the control signal forming means is adjusted. Then set the level of each chroma signal above! Do one verse.

[Embodiment] FIG. 1 shows a block diagram of an embodiment of an auto white balance device to which the present invention is applied. Information R/G and B/G regarding color temperature detected by the auto white balance white balance sensor shown in FIG. 1 are amplified by inverting amplifiers 3 and 4, respectively. The inverting amplifier 3 (4) is an operational amplifier 3a (4a
) to resistors 3b (4b), 3c (4c), 3d (4d
), and nonlinear elements such as thermistors are not used. These amplified signals are sent to the LPF 5.6 to suppress ripple components contained in fluorescent lights, etc., and then sent to the microcomputer 8, where they are converted into digital values by the internal A/D converters 9 and 10. converted. The signal converted into a digital value is sent to a data curve converter 11.12. The outputs of the data curve converters 11 and 12 are converted back to analog values by D/A converters 13 and 14 with latches, and then converted to analog values by the DC level shift circuit 15.

After DCC level summation with the imaging signal processing circuit 18 is performed in step 16, the signal is input to the imaging signal processing circuit 18 as a white balance control signal, and the gain control amplifier 1.9, 20 in the same processing circuit 18 outputs the chroma signal R. , B gain control is performed. The output of the gain control amplifiers 19, 20 is sent to the chrominance signal processing circuit.

Here, the amplified output voltage of the white balance sensor taken into the data curve converter 1.1.12 changes depending on the ambient temperature Ta, and the white The color temperature of the light incident on the balance sensor 1 changes as shown in FIG. The data curve converter 11.12 converts the input voltage (required voltage) of the white balance control signal to the curve shown in FIG. 3(C) so that it can be changed as shown in FIG. 3(B). Perform data conversion.

On the other hand, the temperature sensor 21 for detecting the ambient temperature is disposed at a position where the temperature is commonly used for both the white balance sensor 11, the inverting amplifiers 3 and 4, and the imaging signal processing circuit 18. The output of this temperature sensor 21 is amplified by an inverting amplifier 22, then converted to a digital value by an A/D converter 23, and inputted to the data curve converter 1.1.12 of the microcomputer 8.

The conversion data of the data curve converter 1.1.12 is provided as a ROM table, and the ambient temperature detected by the temperature sensor 21 is input to the data curve converter 1.1.12. The values of the color temperature information R/G and B/G of the white balance sensor 1 are converted according to the above.

Next, the temperature compensation sequence operation of the microcomputer 8 will be explained in more detail using the flowchart shown in FIG. First, information R/G from the white balance sensor 1 is taken in, and then information B/G is taken in.

As described above, the output information of the white balance sensor taken into the microcomputer 8 changes depending on the ambient temperature Ta, and as shown in FIG. It changes linearly with respect to information (mired). After this, temperature sensor 2
Information on the ambient temperature Ta is taken in from 1.

Then, according to the data table of the data curve converter 11, the above information R/G is converted to (R/G) 1, and the above information B/G is converted to (B/G) 1 according to the data table of the data curve converter 12. Convert to After this, from the information of the ambient temperature Ta taken in from the temperature sensor 21, at the data curve conversion section]1°12, (R/G)
(B/G) □1'1 Compensation voltage values ΔTa R, ΔTaB are expressed as p or,
For example, it is determined by data conversion using a data table that describes the characteristics shown in FIG. Next, the above (R/G
) Add the compensation voltage value ΔTaR to 1 to make (R/G), and add the compensation voltage value ΔTaB to the above (B/G) to make (B/G) 2, and then convert these data to D/A. Transfer to converter 3.14 and exit. therefore,
The D/A converters 13 and 14 each have (R/G)
(B/2″G)2 is latched and these values are given as control signal voltages to the gain control circuits 19 and 20 through the DC level shift circuits 15 and 16, respectively, and the control signal voltages change the chroma signals R and B. This adjusts the level of
White balance adjustment is performed with temperature compensation taken into account.

In the embodiment shown in FIG. 1 above, the outputs of the LPF 5.6 are input to individual A/D converters 9 and 10 for A/D conversion, but for example, as shown in FIG. As shown above, the output of the LPF 5°6 is input to one A/D converter 26 via the multiplex 25 which is switched by the switching signal from the white balance microcomputer, and the A/D converted white balance sensor 1 ( (See Figure 1) information R/G.

As described above, the amplified signal regarding B/G may be subjected to data curve conversion in accordance with the ambient temperature Ta detected by the temperature sensor 21 (see FIG. 1) in the microcomputer 27.

[Effects of the Invention] As described above, according to the present invention, it is possible to adjust the constant of the element as in the case where temperature compensation is performed by adjusting each chroma signal output of the white balance detection circuit individually using a nonlinear element such as a thermistor. There's nothing complicated about what you're looking for. Furthermore, the configuration is simplified because temperature compensation can be performed for both the white balance sensor and the level adjustment section for each chroma signal based on the output of a single temperature sensor.

[Brief explanation of the drawing]

FIG. 1 is an auto white balance to which the present invention is applied. FIG. 2 is a flowchart 1 showing the sequence operation of temperature compensation of the microcomputer in FIG. , a diagram for explaining the data conversion action of the data curve conversion unit in FIG. 1, FIG. 4 is a diagram showing an example of compensation voltage characteristics with respect to ambient temperature, and FIG. Fig. 6 is a block diagram showing an example of conventional auto white balance, and Fig. 7 shows how the color temperature is adjusted according to changes in ambient temperature. A diagram showing how the output voltage characteristics of the white balance sensor change with respect to information (mired). Figure 8 shows the required voltage characteristics of the imaging signal processing circuit with respect to color temperature information (millet) in response to changes in ambient temperature. FIG. 1... White balance sensor 8, 27 Microcomputer (control signal forming means) 11, 12... Data curve conversion section (control signal forming means) 21... Temperature sensor

Claims (1)

[Claims] (1) In an auto white balance system that adjusts white balance by adjusting the level of each chroma signal based on the output value of the white balance detection circuit, the temperature related to the white balance detection circuit and the level of each chroma signal are Each of the above chroma An auto white balance system comprising: a control signal forming means for obtaining a control signal for adjusting a signal level;