JPH0334278B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a white balance correction device for a color imaging device.

Generally, in a color imaging device, the red primary color signal E _R obtained as the color imaging output, the edge primary color signal
E _G , and the three primary color signals E _R , E _G , and the blue primary color signal E _B ,
At E _B , a luminance signal E _Y , a red primary color difference signal E _R -E _Y , and a blue primary color difference signal E _B -E _Y are formed, and each of these signals E _Y , E _R -E _Y , E _B - _E
It is designed to synthesize and output NTSC color composite video signals. In order to obtain a color image with faithful color reproducibility using the above color composite video signal, each primary color difference signal E _R −E _Y , E _B −E _Y with accurately maintained white balance is supplied to the encoder. There is a need to.

When a standard white subject is imaged _, white balance _{correction in a color imaging device is performed using three primary color signals E R , E G ,} Each signal level of E _B is E _R =
Each of the above primary color difference signals E _R −E _Y , so that E _G =E _B.
This is done by adding or subtracting a correction signal from E _B −E _Y respectively.

However, in the conventionally widely used white balance adjustment device, each primary color difference signal E _R −E _Y ,
Using a first level adjuster and a second level adjuster that independently and variably adjust the signal level of each correction signal applied to E _B -E _Y , each of the primary color difference signals E _R -
The signal levels of _{E Y} and _{E B} −E _{Y are} expressed _as
Since the correction was made by varying the white balance along the axis, it was generally difficult to find the best white balance correction amount using a level meter or the like.
Therefore, with conventional white balance correction devices,
For example, a first level adjuster and a second level adjuster that variably adjust the signal level of each correction signal are repeatedly operated alternately to obtain an appropriate white balance point through critical adjustment operations. .

If the imaging conditions do not change, there is no need to change the correction amount of white balance correction as described above, but in general, the imaging location, proof light source, etc. are often changed when imaging, so the imaging conditions Each time the value changes, complicated adjustment operations such as those described above must be performed. Furthermore, even when imaging is always performed at the same imaging location, the color temperature of the illumination light source generally changes over time, so the white balance must be corrected in accordance with the change in color temperature. Furthermore, the white balance may be corrected depending on the type of filter attached to the optical system of the imaging device or the type of film used, such as in a color imaging device for transporting film images.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a white balance correction device that can correctly perform white balance correction performed in accordance with various imaging conditions as described above with simple operations. Another object of the present invention is to provide a white balance correction device capable of correcting changes in imaging conditions over a wide correction range.

Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment.

FIG. 1 is a basic configuration diagram showing a first embodiment of a color imaging device to which a white balance adjustment device according to the present invention is applied.

In FIG. 1, an imaging output unit 1 of a color imaging device outputs three primary color signals E _R ,
_EG and _EB are supplied to the matrix circuit 2. The matrix circuit 2 outputs the three primary color signals at a ratio specified in a predetermined standard television system.
E _R , E _G , _and E _B are combined to form a luminance signal EY, as well as a red primary color difference signal _ER - _EY and a blue primary color difference signal _EB - _EY . The luminance signal E _Y formed by this matrix circuit 2 is supplied to a white balance correction circuit 3 and an encoder circuit 4.
Further, the primary color difference signals E _{R -EY} and E _{B -EY} formed by the matrix circuit 2 are supplied to the encoder circuit 4 via the white balance adjustment circuit 3 . The encoder circuit 4 has a luminance signal
E _Y and each primary color difference signal E _R −E _Y , E _{B −E}
By performing signal processing according to the method, a color composite video signal is output from the output terminal 5.

Here, in the NTSC system, E _Y = 0.299E _R + 0.587E _G + 0.114E _B ... Since the luminance signal E _Y is specified as shown in the first equation, this first The signal synthesis of the formula is performed in the matrix circuit 2, and the color composite video signal E _NTSC is expressed in color difference format as E _NTSC =E _Y +1/1.14(E _R −E _Y )・cosωt +1/2.03 (E _B −E _Y )・sinωt...Since it is specified as shown in the second equation,
By performing this second type of signal processing in the encoder circuit 4, a color composite video signal compatible with the NTSC system can be obtained at the output terminal 5.

In this embodiment, the white balance correction circuit 3 provided between the matrix circuit 2 and the encoder circuit 4 is configured as follows. That is, this white balance correction circuit 3 receives the red primary color difference signal from the encoder circuit 4.
First to third signal input terminals 11 _R , 1 to which E _R -E _Y , blue primary color difference signal E _B -E _Y , and luminance signal E _Y are supplied.
1 _B and 11 _Y , each primary color difference signal E _R −E _Y , E _B −E _Y
The first and second signal input terminals 11 are supplied with
_R , 11 _B are the first and second signal adders 12 _R , 12 _B
The third signal input terminal 11Y, to which the luminance signal _EY is supplied, is connected via an inverter ₁₃ to a first pair of level adjusters _14R ,
14 _B and a second pair of level adjusters 14 _R ′,1
4 Connected to _B '.

The first pair of level adjusters 14 _R and 14 _B
is composed of two variable resistors 15 _R and 15 _B. One fixed terminal a 1 of the variable resistor 15 _R constituting one level adjuster 14 _R is connected to the output terminal of the inverter 13 , and the other fixed terminal _{b 1 is} connected to the output terminal of the inverter 13 . It is connected to the input terminal, that is, the third signal input terminal _11Y , and further, the movable terminal _c1 is connected to the third signal adder _12R ' via a non-inverting buffer amplifier _16R . Also, the other level adjuster 14 _B
One fixed terminal a ₂ of the variable resistor 15 _B constituting the variable resistor 15 B is connected to the third signal input terminal 11 _Y , and the other fixed terminal b ₂ is connected to the inverter 13
The movable terminal _c2 is further connected to the fourth signal adder _12B ' via a non-inverting buffer amplifier _16B .

That is, the level adjuster 1 forming the first pair
4 _R and 14 _B are composed of two variable resistors 15 _R and 15 _B connected in parallel in a cross-section between the input and output terminals of the inverter 13 connected to the third signal input terminal 11 _Y. and the third signal input terminal 11
The brightness signal E _Y supplied to _Y is connected to the variable resistor 15 _R , 1
5 _B , and the buffer amplifier 16
Correction signals of opposite polarity to each other via _R , 16 _B -
Outputs ΔE ₁ and +ΔE ₂ . The above correction signal −ΔE ₁ , +
The signal level of ΔE ₂ is variably adjusted in an antiphase manner by the interlocking operation of the first pair of level adjusters 14 _R and 14 _B.

Further, the level adjuster 14 forming the second pair
_R ′, 14 _B ′ are two variable resistors 15 _R ′, 15
It is composed of _B '. The variable resistor 15 _R ' that constitutes one level adjuster 14 _R ' is
One of the fixed terminals a ₃ is connected to the output terminal of the inverter 13, and the other fixed terminal b ₃ is the input terminal of the inverter 13, that is, the third signal input terminal 1.
_1Y , and the movable terminal _c3 is further connected to the third signal adder _12R ' via a non-inverting buffer amplifier _16R '. Also, the variable resistor 15 constituting the other level adjuster 14 _B '
_B ' has one fixed terminal _a4 connected to the third signal input terminal _11Y , the other fixed terminal _b4 connected to the output terminal of the inverter 13, and further,
A movable terminal _c4 is connected to the fourth signal adder _12B ' via an inverting buffer amplifier _16B '.

The second pair of level adjusters 14 _R ', 14
_B ' consists of two variable resistors _15R ' and _15B ' connected in parallel in a cross-section between the input and output terminals of the inverter 13 connected to the third signal input terminal _11Y . , the luminance signal E _Y supplied to the third signal input terminal 11 _Y is connected to the variable resistor 15 _R ′, 15
_B ' attenuates the buffer amplifier 16.
Correction signals of the same polarity are transmitted through _R ' and _16B '.
Outputs ΔE ₃ and −ΔE ₄ . The above correction signal −ΔE ₃ , −
The signal level of ΔE ₄ is variably adjusted in phase by the interlocking operation of the second pair of level adjusters 14 _R ′ and 14 _B ′.

The third signal adder _12R ' receives the correction signal - supplied from the level adjusters _14R , _14R ' via buffer amplifiers _16R , _16R ', respectively.
ΔE ₁ and −ΔE ₃ are added and combined to produce the first correction signal ΔE _Y13
and converts this first correction signal ΔE _Y13 into the first correction signal ΔE Y13.
The signal is supplied to the signal adder _12R . In addition, the fourth
The signal adder _12B ' is connected to the level adjuster _14B ,
14 _B ' to buffer amplifiers 16 _B and 16, respectively.
The correction signals +ΔE ₂ and −ΔE ₄ supplied via the circuits _B ′ are added and combined to form a second correction signal ΔE _{Y24, and this second correction signal ΔE Y24 is} sent to the second signal adder _12B. supply to. The other correction signal _-ΔE4 supplied to the fourth signal adder _12B ' is obtained by inverting the polarity of the correction signal + _ΔE4 from the level adjuster _14B ' by the inverting buffer amplifier _16B '. It is something.

This white balance correction circuit 3 is
The first signal adder 12 _R adds and synthesizes the first correction signal ΔE _Y13 to the red primary color difference signal E _R −E _Y from the first signal input terminal 11 _R , and the second signal adder 12 _R
By adding and synthesizing the second correction signal ΔE _Y24 to the red primary color difference signal E _B −E _Y from the second signal input terminal 11 _B , a primary color difference signal E _R −E whose white balance has been corrected is obtained. Outputs _Y , E _B −E _Y.

Adjustment of the amount of correction in the white balance correction circuit 3 is performed using correction signals -ΔE ₁ , -ΔE ₃ which become the first correction signal ΔE _Y13 and correction signals -ΔE ₂ , +ΔE which become the second correction signal ΔE _Y24 . Among the signal levels of ₄ , correction signals of opposite polarity −ΔE ₁ , +
The signal level of ΔE ₂ is variably adjusted in an antiphase manner by interlocking operation of the first pair of level adjusters 14 _R and 14 _B , and correction signals −ΔE ₃ ,
-ΔE ₄ is variably adjusted in phase by interlocking operation of the second pair of level adjusters 14 _R ′ and 14 _B ′.

That is, in this white balance correction circuit 3, when the white balance point W _P is monitored with a vector scope, as shown in FIG.
The white balance points W _P on the orthogonal coordinate plane formed by the E _R -E _Y axis and the E _B -E _Y axis are opposite to each other due to the interlocking operation of the first pair of level adjusters 14 _R and 14 _B. By variable adjustment of the signal levels of the polarity correction signals -ΔE ₁ and +ΔE ₂ in a negative phase manner, the polarity is moved across the second quadrant D ₂ and the fourth quadrant D ₄ of the orthogonal coordinate plane, and Second pair of level adjusters 1
By interlocking operations of 4 _R ' and 14 _B ' and variable adjustment of the signal levels of correction signals -ΔE ₃ and -ΔE ₄ having opposite polarities, the first quadrant of the orthogonal coordinate plane is
_D1 and the third quadrant _D3 .

Here, since the change in color temperature of a light source generally used for imaging, such as an incandescent light bulb or sunlight, is considered to approximate the temperature change of black body radiation, the axis of the black body locus P _L 1. Move the white balance point W _P along the
By operating the pair of level adjusters 14 _R and 14 _B in conjunction with each other, white balance correction can be performed over a wide temperature range. In the white balance correction circuit 3 of this embodiment, by the interlocking operation of the first pair of level adjusters 14 _R and 14 _B , as shown by solid line arrows in FIG.
The _buffer amplifier _{16R ,}
Gains A ₁ and A ₂ of 16 _B are set. Also, by the interlocking operation of the second pair of level adjusters 14 _R ′ and 14 _B ′, as shown by the broken line arrow in _FIG . The _buffer amplifiers 16 _R ′, 16
Gains A ₃ and -A ₄ of _B ' are set.

In the white balance correction device of this embodiment,
The first pair of level adjusters 1 performs white balance correction for changes in color temperature of general light sources.
4 _R and 14 _B can be easily performed by interlocking operations, and the second pair of level adjusters 14 corrects white balance for changes in color temperature caused by filters etc. that are unrelated to black body radiation. _R ′,1
This can be done by the interlocking operation of 4 _B '. Therefore, in the white balance correction device of this embodiment, the first pair of level adjusters 14 _R , 1
4 _B and the second pair of level adjusters 14 _R ',
The white balance can be correctly corrected over a wide color temperature range by an extremely simple adjustment operation that involves operating the 14 _B ' in conjunction with each other.

In addition, in the above-mentioned embodiment, two sets of variable resistors were used as each pair of level adjusters, but
For example, it is also possible to use level adjustment means that combines a single variable resistor and a differential amplifier.

As described above, according to the present invention, the blue primary color difference signal E _B -E _Y and the red primary color difference signal E _R -E _Y are adjusted by interlocking operation of the first pair of level adjustment means in a reverse phase manner. By varying the signal levels of the correction signals ΔE _Y13 and ΔE _Y24 in an antiphase manner, the white balance point is set to the second point on the rectangular coordinate plane formed by the E _B −E _Y axis and the E _R −E _Y axis.
Since it is made to move across the quadrant and the fourth quadrant, the white balance can be corrected correctly with a simple adjustment operation. In addition, the first
By moving the white balance point along the axis of the blackbody locus by interlocking the pair of level adjustment means in an antiphase manner, the white balance can be corrected over a wide range.
moreover,. By in-phase interlocking operation of the second pair of level adjustment means, the signal levels of the correction signals ΔE _Y13 and ΔE _Y24 are varied in-phase, and the white balance point is set between the first quadrant and the first quadrant on the rectangular coordinate plane. By moving it across three quadrants, it is easy to operate even when the color temperature changes due to the type of film used in the filter optically attached to the image pickup device or the type of film used in the image pickup device for transporting film images. You can correct the white balance correctly.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the configuration of a white balance correction device according to the present invention. FIG. 2 is a vector diagram showing, on a vector scope, the movement status of a white balance point when white balance correction is performed by the white balance correction device shown in FIG. 1... Imaging unit, 2... Matrix circuit, 3...
White balance correction circuit, 4... Encoder circuit, 11 _R , 11 _B , 11 _Y ... Signal input terminal, 1
2 _R , 12 _R ', 13 _B , 13 _B '...Signal adder, 1
3...Inverter, 14 _R , 14 _R ', 14 _B , 14
_B '...Level adjuster, 15 _R , 15 _B , 15 _R ', 1
5 _B ′...Two variable resistors, 16 _R , 16 _R ′, 1
6 _B , 16 _B '...Buffer amplifier.

Claims (1)

[Claims] 1. First to third channels to which the red primary color difference signal E _R -E _Y , the blue primary color difference signal E _B -E _Y , and the luminance signal E _Y formed from the imaging output of the color imaging device are supplied. a first signal adder that adds a correction signal ΔE _Y13 to the red primary color difference signal E _R −E _Y supplied from the first signal input terminal; a second signal adder that adds a correction signal ΔE _Y24 to the supplied blue primary color difference signal E _B -E _Y ; a polarity inverter to which the luminance signal E _Y is supplied from the third signal input terminal; They are respectively connected between the third signal input terminal and the output terminal of the polarity reversing means, and are operated in conjunction with each other in opposite phases to form correction signals ΔE ₁ and ΔE ₂ of mutually opposite polarity from the luminance signal _EY . a first pair of level adjusting means, which are connected between the third signal input terminal and the output terminal of the polarity reversing means, are operated in phase with each other, and are connected to each other from the luminance signal _EY. a second pair of level adjusting means forming correction signals ΔE ₃ and ΔE ₄ of the same polarity; and a correction signal ΔE ₁ formed by the first pair of level adjusting means forming the second pair. A correction signal ΔE _Y13 for red primary color difference signal E _R −E _Y correction is obtained by adding the correction signal ΔE ₃ formed by the level adjustment means.
a third signal adder for forming a correction signal ΔE ₂ formed by the first pair of level adjustment means and a correction signal ΔE ₄ formed by the second pair of level adjustment means. Adding blue primary color difference signal E _B −E _Y correction signal ΔE _Y24
and a third signal adder for forming the blue primary color difference signal E _B -E _Y and the red primary color difference signal E _R - by continuous operation of the first pair of level adjustment means in an opposite phase. Each correction signal ΔE _Y13 given to E _Y ,
By varying the signal levels of ΔE _Y24 in an antiphase manner, the white balance point is set in the second and fourth quadrants on the rectangular coordinate plane formed by the E _B −E _Y axis and the E _R −E _Y axis. At the same time, the signal levels of the correction signals ΔE _Y13 and ΔE _Y24 are varied in phase by the in-phase interlocking operation of the second pair of level adjustment means, and the white balance point is adjusted to the above-mentioned value. A white balance correction device characterized in that it is moved across a first quadrant and a third quadrant on a rectangular coordinate plane. 2. The white balance point is moved along the axis of the black body locus by the anti-phase interlocking operation of the first pair of level adjusting means, and the in-phase interlocking operation of the second pair of level adjusting means 2. The white balance correction device according to claim 1, wherein the white balance point is moved along an axis perpendicular to the axis of the blackbody locus by operation.