JPH03185988A - White balance system - Google Patents

Abstract

PURPOSE:To eliminate need for a special externally mounted component and to simplify the constitution by converting an output of a photoelectric conversion section into a current so as to charge and discharge a capacitor thereby outputting the result as a voltage output or a time output. CONSTITUTION:Photoelectric conversion sections 11, 12 output a voltage in response to light sources 23, 24 representing the color characteristic of light and voltage current conversion sections 21, 22 apply current conversion in response to an output voltage of the photoelectric conversion sections 21, 22. The current output charges/discharges a capacitor 5 via switches 7, 8 to output a voltage or a time. Through the constitution above, a current ratio generated in response to the light in the light sources 23, 24 is obtained, and for example, when the light source 23 radiates a light in response to red light wavelength area and the light source 24 radiates a light in response to blue light wavelength area, since the distribution ratio of the blue and red wavelength areas of the light sources 23, 24 is obtained, the characteristic of the light sources 23, 24 required for controlling white balance is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance sensor output section of a video camera or the like.

[Conventional technology]

FIG. 7 is a block diagram of a conventional white balance system. In the figure, (1) is a diode, (2) is an amplifier, (6) is a photosensor, (If), Q2) is a photoelectric conversion unit, a is a power supply, @, Q@ are a light source, ■ is an output, O
Old calculation circuit, @ is temperature correction, (7) is A/D conversion.

A light source that expresses the characteristics of light using color filters, etc.

(to) is input to a photosensor (6) such as a photodiode, and a photoelectric conversion unit Q composed of a diode (IIDI, D2. amplifier (2) AI, A2) is inputted to a photosensor (6) such as a photodiode.
l), (121 outputs it as a voltage signal. The output voltage is subjected to temperature correction (2) through a subtraction circuit 6Φ and outputted as an output (aS)VOUT. In the case of digital control, the output @VOUT is subjected to A/D conversion ω.

Next, the operation will be explained. According to the light source ■, c2@, the photo sensor (61P1. The current ILI generated in P2,
IL2 is a diode (1), and the voltage is converted by D2. The output voltages Vl and V2 at this time are as follows.

k; Boltzmann constant q; charge T; absolute temperature l5nu
i diode (11D 1 forward saturation current ■sD2;
Forward saturation current of diode (1) D2, then subtraction circuit O
The output of Φ is as follows, and the characteristics of the light source (to), c2@, can be expressed as the ratio of ILI and IL2. Since this output is proportional to T, it is output after temperature correction.

[Problem to be solved by the invention]

Conventional white balance systems are configured as described above, which requires temperature correction using an external temperature-sensitive resistor, and also has problems such as the need for external A/D conversion for digital output. There was a point.

This invention solves the above-mentioned problems and makes it possible to configure a white balance sensor capable of analog or digital output with a simple configuration, thereby providing a white balance system that does not require special external parts. The purpose is to

[Means to solve the problem]

In this invention, the output of the photoelectric conversion section for white balance is converted into a current, and the capacitor is charged and discharged with the current.
It is designed to output voltage or time.

[Effect]

In the white balance system according to the present invention, the output of the photoelectric conversion section for white balance is converted into a current to charge and discharge a capacitor.

〔Example〕

FIG. 1 is a block diagram of a white balance system according to an embodiment of the present invention, FIG. 2 is a sequence diagram showing signal waveforms of each part of FIG. 1, and FIGS. 3 and 5 are respectively other embodiments of the present invention. A block diagram of a white balance system according to an example, FIG. 4 is a sequence diagram showing signal waveforms of each part in FIG. 3, and FIG. 6 is a sequence diagram showing signal waveforms of each part in FIG. In the figure (11, +21, (8
1, OD, (2), 09° (to), (to), ■ are the same as those shown in the conventional example of FIG. 7, and therefore their explanation will be omitted. (3) is an amplifier, (4) is a comparator, (5) is a capacitor, (7) to QOI are switches, and (13).

0 is a level shifter, 09 is a counter control logic.

00 is constant current source, (+7), Gυ, ■ is power supply, Ql
), C121 is the voltage.

This is a current converter (hereinafter referred to as a VI converter).

Photoelectric conversion units 01) and (2) are light sources that exhibit color characteristics of light;
Voltage output is performed according to (to). VI converter Ql)
, C12 performs current conversion according to the output voltages of the photoelectric conversion units (11) and (2). The current output is a switch (71S
, , via switch (8) S2, capacitor (5)
It is designed to charge and discharge C. The amplifier (3) and the capacitor (5) C constitute an integrating circuit that outputs the results of charging and discharging as a voltage.

In FIG. 1, the photoelectric conversion sections (11, 02) are constructed by level-shifted and appropriately biased transistors. Power supply 07) and GID each have a bias potential VEI p VH2, and level shifter C13)
, (1@ shift amount VLI p VL2 may be fixed or variable.

The output current can be set to an optimal value by making it variable.

In FIG. 2, the sequence is such that an output corresponding to the light source (to) can be obtained after the light source (to), but the order does not matter in particular. Output current according to light source ■, @11.
I has the following relational expression.

■! = A x nl IL+ That is, l1=AntIta ~ ■ Similarly, 12-Bn211-2 ~ ■ In Figure 1, when the switch (91S3) is turned on and the charge of the capacitor (5) is discharged, the output (5) V OUT
If the power supply (2) is reset to VD. Next, switch (7
) When S1 is turned on, the capacitor (5) C is charged with the output current ■ expressed by the formula ■, so similarly, when the switch (81S2) is turned on after reset, the capacitor (5) C is charged with the output current ■ expressed by the formula ■. 5) Since C is charged, if we calculate the ratio of VOI and VO2, we can find the ratio of the current generated in the light source (to) and □□□ in response to the light.For example, if the light source (to) is red If the light wavelength range and the light source (to) are input light according to the blue light wavelength range, the distribution ratio of the red and blue wavelength ranges of the light source (23) and (to) can be found, that is, the white It is possible to detect the characteristics of the light source (to) and c2@ required for balance control.

■As you can see from the formula, ni, n2. A, B, T.I.
, T2 can be set as known quantities and do not depend on temperature, so there is no need for temperature correction.

In Fig. 3, the output current corresponding to the light source (to) is V-I converted in the direction of flowing out, and as shown in Fig. 4, the light source (to) is
The capacitor (5) C is charged with an output current 11 corresponding to the time T□ and then discharged with I2, and the amplifier (3)
When the output VOUT reaches the reset level power supply (E) VD, the signal V is output by, for example, a comparator (4). I tried to issue the following. This signal ■. V from the start of discharge due to I2. The time T until it appears. output using a counter etc. so that it can be measured.

At this time, the distribution ratio of the output current corresponding to the light source ■) and (company), that is, the distribution ratio of the light source ■, (to) can be obtained as the time ratio T (+ / Tl. As can be seen from the formula ■ The color characteristics of , light source (to), and @ can be directly output as digital quantities regardless of temperature.

Figure 5 shows the charging and discharging of capacitor (5)C between the light source (to) and (
The output current of the comparator (4) is determined by the current 1r of the reference constant current source 0ω and the output current of the comparator (4) as shown in FIG. The time ratio of 1 and T (of the light source) and (to) the color characteristic ratio can be obtained.

In any of the above embodiments, the level shift amount VL, p
VL2 p V I converter an, o2 applied voltage V
Itl, VIE2 switch control time Ti, 'r2.
By setting the Tr and the reference current Ir according to the input intensity of the light source (to) and (to), it is possible to always obtain an output with high accuracy. In this case, the above set value may be varied after monitoring the -power level or by monitoring the state of the light amount in a separate system.

Furthermore, the direction and sequence of current can be freely set.

〔Effect of the invention〕

As described above, according to the present invention, since the output corresponding to the input light source is obtained by charging and discharging the capacitor with current, there is no need for special parts, there is no temperature dependence, and highly accurate white balance control is achieved. The values can be obtained as analog or digital quantities.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a white balance system according to an embodiment of the present invention, Fig. 2 is a sequence diagram showing signal waveforms of each part of Fig. 1, and Figs. A block diagram of the white balance system according to the embodiment, FIG. 4 is a sequence diagram showing signal waveforms of each part in FIG. 3, FIG. 6 is a sequence diagram showing signal waveforms of each part from ζ to FIG. 5, and FIG. 7 is a conventional FIG. 2 is a block diagram showing a white balance system. In the figure, (1) is a diode, (21, (31 is an amplifier), (4) is a comparator, (5) is a capacitor, (6) is a photosensor. Q; t) is a photoelectric conversion unit, 03), (+4) is a level shifter, 00
is the counter control logic, θ0 is the constant current source, 07) ~ (
A) is the power supply, ci>, a is the V-I converter, @, (to)
is the light source, and (5) is the output. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] It has at least two or more photoelectric conversion units that detect the characteristics of the light source, and a voltage-current conversion unit that outputs the output voltage of the photoelectric conversion unit as a current output, and charges and discharges a capacitor with the output current of the voltage-current conversion unit. A white balance system characterized by voltage output or time output.