JPS63278480A - Automatic white balance device - Google Patents

Abstract

PURPOSE:To accurately operate a device even for a light source having a specific spectral characteristic such as a light lamp, by converting the value of a conversion table corresponding to the size of an AC component obtained by detecting the AC component included in the output voltages of two or more photoelectric transducers. CONSTITUTION:The titled device is constituted in such a way that logarithmic amplifiers 2a-2c which apply logarithmic compression on at least one output out of the outputs of the photoelectric transducers 1a-1b and an AC component detector 5 which detects the AC component of the output voltages of the logarithmic amplifiers 2a-2c are provided, and the values of the conversion tables of table converters 6a, 6b, and 7 corresponding to the size of the output of the AC component detector 5 are is varied. In such a way, it is possible to perform prescribed white balance with high accuracy by computing a ratio of the AC component to all of the light quantities and varying a gain control voltage based on a computed value even in a case of using discharge lamp illumination such as a fluorescent lamp, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention primarily relates to an automatic white balance device applied to a color video camera device.

[Prior Art] FIG. 3 is a block diagram showing the configuration of a conventional automatic white balance device, which is often adopted in home color video camera devices. (lb), (lc) are photoelectric conversion elements, (2a), (2b), (2c) are logarithmic amplifiers connected to the photoelectric conversion elements (la), (lb), (lc), respectively, (Fa) , (:lb), (3c) are the logarithmic amplifiers (2a), (2b).

Smoothing circuits connected to (2c), (4a),
(4b) is the smoothing circuit (3a), (:lb), (3
c) a subtraction circuit for calculating the difference between two of the outputs;
(6a) and (6b) are the subtraction circuits (4a) and (4
(13) converts the outputs of the A/D converters (6a) and (6b) into tables using them as two independent variables to generate two outputs. It is an arithmetic circuit that performs

(9) is an image sensor; (10) is a color signal separation circuit (Ila) that separates a color signal from the output of the image sensor (9);

(llb) is a variable gain amplifier that varies the amplitude of the color signal output from the color signal separation circuit (10) according to the output of the arithmetic circuit (13); (12) is a variable gain amplifier suitable for processing the color signal in a subsequent stage; This is an encoder that converts the signal into a signal.

Next, the operation of the above configuration will be explained.

The photoelectric conversion elements (la), (lb), and (lc) are each set to have different spectral sensitivity characteristics, and have three independent output voltages (Er) for the wavelength distribution of external light.
, (Eg) and (Eb) are generated. When the above external light includes illumination light from a discharge lamp light source such as a fluorescent lamp, the above output voltages (Er), (Eg), and (Eb) are AC components with a frequency twice the frequency of the power supply voltage of the light source (hereinafter referred to as , also called ripple component). This output voltage (Er)
, (Eg), (Eb) are logarithmic amplifiers (2a), (2b
) and (2c), respectively. A logarithmic amplifier (2a), (
The output voltages of 2b), , (2c) change. The output voltage (EL
r), (ELg), (ELb).

El, r m a conflict log(Er) +
βELg = a − log (Eg) + β α, β are constants −(1) ELb = a − log (Eb) + β.

As mentioned above, each of the photoelectric conversion elements (la), (lb
).

Since the output voltages (Er), (Eg), and (Eb) of (lc) include ripple components, this logarithmic amplifier (2a)
, (2b), (2c) output voltage (ELr), (
ELg) and (ELb) also include ripples.

Next, in the smoothing circuits (3a), (:lb), (:lc), the above output voltages (ELr), (ELg), (EL
b) Smooth the ripple included in the output voltage (E
Lr), (ELg), (ELb) time average voltage (
Er), (Eg), and (Eb) are output, and the subtraction circuit (4a
), (4b), the differences (Er-'Eg) and (Eb-Eg) between the time-average voltage combinations are output. Here, the above output voltages (Er), (Eg),
(Eb) is proportional to the brightness of external light, and the time average voltage (Er
), (Eg), (Eb) are the output voltage (
For the logarithm of (Er), (Eg), (Eb), (
Since formula 1) is satisfied, the subtraction circuits (4a) and (4b
) is (Er-Eg)-log(Er/Eg)...(2) (Eb-Eg)" log(Eb/Eg), which corresponds to the voltage ratio of the combination of two photoelectric conversion elements. do.

Next, in the A/D converters (6a) and (6b).

After quantizing the outputs of the subtraction circuits (4a) and (4b), the arithmetic circuit (13) ends up with a photoelectric conversion element (la
) and (1b) and the ratio of the incident light amount of the photoelectric conversion element (la
Two data corresponding to the ratio of the amount of incident light between ) and (lb) are input. In this arithmetic circuit (1 circuit), table conversion is performed using a two-dimensional table that makes the two input data independent changes, and the control voltage (Ar),
(Ab) is output. This arithmetic circuit (13) uses a microcomputer and uses a ROM as a table for conversion. In this case, the control voltage output (Ar), (Ab
) may be output after D/A conversion.

On the other hand, the signal obtained by the image sensor (9) is input to the color signal separation circuit (10) and is divided into three independent color signals (
R), (G), and (B). Of these color signals, (R) and (B) are transmitted through variable gain amplifiers (Ila) and (Ia).
lb) and this variable gain amplifier (lla), (
llb), the control voltage output (Ar), (
The gain is controlled in proportion to Ab). This color signal is then input to an encoder (12) and converted into a signal suitable for subsequent processing.

In an automatic white balance device with such a configuration,
By setting the conversion table of the arithmetic circuit (13) that performs table conversion to an appropriate value determined by the spectral characteristics of the photoelectric conversion elements (Ia), (lb), (Ic) and the spectral characteristics of the image sensor (9). Even when the color temperature of external light takes on various values, the color signal input to the encoder (12) can be kept constant, and a predetermined white balance operation can be performed.

[Problems to be Solved by the Invention] Since the conventional automatic white balance device is configured as described above, the photoelectric conversion elements (la) and (lb).

It was difficult to set the spectral characteristics of (1c) and the image sensor (9),
Malfunctions are likely to occur when using light sources with special spectral characteristics such as fluorescent lamps, and in order to perform accurate operation, it is necessary to increase the capacity of the conversion table, that is, the number of elements. There were problems such as the fact that they tend to be expensive.

This invention was made to solve the above-mentioned problems, and it can operate accurately even with light sources with special spectral characteristics such as light lamps, and it can be used with a small conversion table as well as the conventional one. An object of the present invention is to provide an automatic white balance device that can obtain a certain level of white balance accuracy.

[Means for Solving the Problems] The automatic white balance device according to the present invention detects an alternating current component included in the output voltage of two or more photoelectric conversion elements, and detects the alternating current component included in the output voltage of two or more photoelectric conversion elements, and The present invention is characterized in that it is configured to convert the values of the conversion table.

[Operation] According to the present invention, the ratio of the AC component to the DC component is obtained by detecting the AC component of the output of the photoelectric conversion element, and this ratio is A/D converted and input to the arithmetic circuit. It is processed. This calculates the proportion of the AC component in the total amount of light and changes the gain control voltage based on the calculated value to achieve a predetermined white balance with high precision even in the case of discharge lamp lighting such as fluorescent lamps. obtain.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a J white balance device according to an embodiment of the present invention, in which the same components as the conventional example shown in FIG. , their detailed explanation will be omitted.

In No. 11, (5) is an AC component detector, and logarithmic amplifiers (2a), (2b), (2c) are connected to the photoelectric conversion elements (la), (Ib), and (Ic), respectively.
An alternating current component in the output voltage of one of the logarithmic amplifiers (2a) is detected. (7) is "-Record AC component detection" 1A (
(5) is an A/D converter that converts the output of (8) into an A/D converter.
D converter (6a).

This is an arithmetic circuit that performs table conversion using the three output voltages (6b) and (7) as independent variables to generate two output voltages.

Next, we will explain the operation of VII.

Three photoelectric conversion elements each with different spectral characteristics (
The output voltage (Er) of la), (lb), (lc)
), (Eg), (Eb) are logarithmic amplifier (2a)
, (2b), (2c) and smoothing circuit (3a)
, (3b) and (3c) to the subtraction circuit (4a),
(4b), log(Er/Eg) and lo
Output voltage ('i:r-Eg) corresponding to g(Eb/Eg)
) Operations to obtain H and (″F, b-100g), operations to quantize these output voltages (Nr-Eg) and (rb-”Mg) by A/D conversion (6a), (6b) is the same as before.

Here, the output voltage (Eg) of the photoelectric conversion element (lb) is
It includes ripples generated by a discharge lamp light source such as a fluorescent lamp at a frequency twice the power supply frequency of the lighting. Therefore, the output voltage (ELg) of the logarithmic amplifier (2b) also includes this ripple. This output voltage (ELg
) is time-averaged in the smoothing circuit (3b), but apart from this, the output voltage (E
Lg) is also guided to an AC component detector (5).

In this AC component detector (5), the output voltage (ELg
), the output voltage (Eg) of the AC component detector (5) is as shown in FIG. 2.

Tg=log ([:g(AC+oc)-10g([:
g(oc))”lOg (Eg(Ac〇’)/E
g(oc)) ...-(:l) where Eg) is the output voltage of the AC component detector (5), and (
The peak voltage value of the AC component of (ELg), (Eg(Ac +
oc) ) is the peak voltage value of the output voltage of the photoelectric conversion element (1b), and (Eg(oc)) is the average value of the output voltage of the photoelectric conversion element (1b).

That is, the output voltage (Eg) of the AC component detector (5) is equal to the ratio of the peak value including the AC component of the output voltage (Eg) of the photoelectric conversion element (lb) and the average value of (Eg), and The voltage corresponds to the ratio between the peak value and the average brightness of external light incident on the conversion element (1b).

Generally, in the case of illumination using a discharge lamp such as a fluorescent lamp or a mercury lamp, the ratio of the peak value to the average value of the usage is large, so the output voltage (I:g) of the AC component detector (5) is large (f
It becomes i, self r &'it! :For bulbs, etc., the ratio of the peak brightness value to the average brightness value is small, so the output voltage (Eg) is also a small value. In addition, the output voltage (Eg) becomes zero under natural light such as sunlight. Furthermore, as is clear from equation (3) above, the output voltage (Eg) of the AC component detector (5) depends only on the ratio between the peak value and the average brightness of the incident external light, and the brightness itself Not related to. Therefore, the output voltage (Eg) has a unique value depending on the type of light source.

The output voltage (Eg) of the AC component detector (5) having the above properties is quantized by the A/D conversion circuit (7), and the two A/D conversion circuits (6a) described above are quantized.

It is input to the arithmetic circuit (8) together with the output of (6b).

In this arithmetic circuit (8), each of the above A/D conversion circuits (
The outputs of 6a), (6b), and (7) are transformed into three independent transformations using a three-dimensional table.
Outputs two control voltages (Ar) and (Ab). This arithmetic circuit (8) can be easily realized by using a microcomputer and using a ROM as a table for conversion. In this case, the control voltage (Ar), (Ab) is D/A
Just convert and output.

On the other hand, the signal obtained by the image sensor (9) is input to a color signal separation circuit (10) and becomes three independent color signals (+1), (G), and (R). Of these color signals, (R) and (B) 4 are transferred to variable gain amplifiers (lla) and (Il).
b) and this variable gain amplifier (lla), (l
lb), the gain is controlled in proportion to the control voltages (Ar) and (Ab). This color signal is then input to an encoder (12) and converted into a signal suitable for subsequent processing.

In the above embodiment, the conversion cheatle for table conversion in the arithmetic circuit (8) is replaced by the charging conversion element (l).
Spectral characteristics of a), (Ib), and (IC) and image sensor (9)
Based on the spectral characteristics of the output voltage (E
For the elements corresponding to the parts where g) is not zero, by setting the control voltage to correspond to artificial lighting such as fluorescent lamps, the color temperature of outside light can take various values. Even in the case of artificial lighting using a discharge lamp such as a fluorescent lamp, the color signal input to the encoder (12) can be kept in an optimal state, and automatic white balance operation can be performed as specified.

In addition, in the above embodiment, three charging conversion elements (la),
(lb) and (lc) are used, but the number of light source conversion elements can be any number greater than or equal to 0.If the number of light source conversion elements is increased, more information about the light source can be obtained, so the accuracy is better. improves.

Further, in the above embodiment, the output voltage (ELg) of the logarithmic amplifier (2b) was input to the AC component detector (5), but (
A similar effect can be obtained by inputting (ELr) or (ELb) instead of El, g).

Furthermore, a configuration may be adopted in which a plurality of AC component detectors are provided and outputs of a plurality of logarithmic amplifiers are processed.

[Effects of the Invention] As described above, according to the present invention, the ripple of discharge lamp lighting such as a fluorescent lamp, which has not been used as information in the past, is also utilized as information, so a special Even for light sources with spectral characteristics, there are fewer malfunctions and the desired automatic white balance can be performed with high precision. Furthermore, compared to the conventional method, a conversion table having a small capacity can achieve an accuracy equal to or higher than that of the conventional method, and the entire device can be made smaller and lower in cost.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an automatic white balance device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram for explaining the input and output voltages of a logarithmic amplifier, and Fig. 3 is a conventional automatic white balance device. FIG. 2 is a block diagram showing the configuration of the device. (la), (lb), (lc)... photoelectric conversion element,
(2a), (2b). (2C)...logarithmic amplifier, (5)--alternating current component detector, (8)...arithmetic circuit. Note that the same reference numerals in Figure 1 indicate the same or corresponding parts.

Claims (1)

[Claims] (1) comprising two or more photoelectric conversion elements and a table converter that performs table conversion using a plurality of data corresponding to a ratio of combinations of outputs of the photoelectric conversion elements as independent variables; the output of the table converter; In an automatic white balance device configured to adjust white balance using a control voltage that
a logarithmic amplifier that logarithmically compresses at least one output; and an AC component detector that detects an AC component of the output voltage of the logarithmic amplifier; An automatic white balance device characterized in that it is configured to change the value of a conversion table.