JPH02272892A - White balance controller - Google Patents

Abstract

PURPOSE:To improve the white balance accuracy by using illuminance information obtained by a stop value detection and illumination information obtained by a fluorescent lamp detection in addition to a color temperature detection obtained by a color difference signal. CONSTITUTION:A correcting circuit 15 provided between a comparative amplifying circuit 14 and a WB(white balance) tracking 17 discriminates illumination conditions (indoor, outdoor, fluorescent lamp, incandescent lamp, etc.), and corrects a WB control signal based on the discrimination result. Only when the fact that the illumination is the fluorescent lamp is decided, a gate 111 in an R+B-2Y signal route is made conductive, and a control in the R+B-2Y axis direction is executed. Thus, even under an artificial illumination such as the fluorescent lamp (not similar to a black body radiation), the white balance control corresponding to the situation can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance adjustment device for a video camera.

[Conventional technology]

As described in Japanese Patent Application Laid-open No. 63-219291, the conventional device extracts a signal from a portion of the photographic screen that can be considered white (or achromatic color), and sets the R:B ratio of the averaged signal of this portion to 1. The red (R
) was configured to subordinately control the gain before death (B).

In addition, in this conventional device, the control signal for white balance adjustment is generated using the averaged signal (voltage) of the white part as described above and the reference signal (voltage) corresponding to R-B (=0) at a certain color temperature. This was done by comparing.

[Problem to be solved by the invention]

The above conventional technology performs appropriate control when there is a white (or achromatic) part that is effective for white balance adjustment in the shooting screen, but when there is no part of the screen that can be considered white at all, the standard adjustment is performed. Fixed in state. The above standard adjustment is set to, for example, 4000 to 500 G'K from the viewpoint of the color temperature change range of practical lighting, but as mentioned above, if there is no white part on the screen and the automatic adjustment does not work, the type of lighting In some cases, there was a problem that the error became large.

The present invention aims to reduce the occurrence of errors in shooting situations where there is no white part at all, and further aims to provide a device that reliably extracts only the white part and achieves accurate white balance. do.

Another object of the present invention is to provide a white balance control device that can perform white balance control according to the situation even under artificial illumination (not similar to black body radiation) such as a fluorescent lamp.

[Means to solve the problem]

In order to achieve the above objective, in addition to color temperature detection using color difference signals (R-Y, B-Y)K, which have been used in the past, illuminance information based on aperture value detection, illumination information based on fluorescent light detection, and external measurement The range and method of white balance adjustment can be changed using color temperature information based on a color sensor, a color signal before white balance adjustment, and the like.

Further, for illumination that does not follow the color temperature locus of black body radiation, control is separately applied in accordance with the deviation from the color temperature locus.

Furthermore, in case there is a concern that the extraction of the white part may become uncertain, the white balance adjustment is temporarily stopped depending on the situation.

[Effect]

In a camera with an automatic exposure function, the approximate illuminance can be determined by detecting the aperture value. Furthermore, the illumination conditions at the time of photographing can be predicted to a certain extent based on the illuminance value. For example, outdoors on a clear day, it is about 10,000 LX or more, on a cloudy day or in the shade, it is about several hundred to 1,000 LX, and indoors it is less than that, and it is also possible to distinguish between incandescent lamps and fluorescent lamps based on the presence or absence of 7 LX. Therefore, the white balance is roughly adjusted based on the aperture value information (the conventional reference adjustment point is shifted), and then fine adjustments are made using the same conventional method.

That is, by making a preliminary judgment based on the illuminance as described above, the target color temperature range can be limited, and since the reference adjustment points are set relatively close to each other for each illumination, it is possible to photograph a subject that has no white parts at all. The adjustment will not deviate significantly even if the

In addition, instead of the aperture value information, coarse adjustment (shifting of the reference point) can also be performed using a colorimetric sensor capable of detecting the ratio of red and blue components of ambient light or red and blue signals before white balance adjustment. .

To temporarily stop white balance adjustment, when the area that can be considered white on the shooting screen is decreasing, store the control data (voltage, etc.) when there is enough white and adjust the white area that occupies the screen. If the area is within a predetermined threshold 1Ii (for example, 20
If the value falls below the threshold value h), the normal adjustment operation is stopped while the value falls below the threshold value, and the state immediately before the threshold value (or the stored control data) is maintained. This can prevent sudden changes in color tone due to uncertainty in white extraction during shooting. Further, by linking the zoom operation and the temporary stop of the white balance adjustment, it is possible to prevent a change in color tone due to a change in the photographing angle of view.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The light passing through the camera 2 lens 1 is adjusted to an appropriate exposure by the diaphragm 2 and is imaged on the image sensor s. The signal processing system 4 generates luminance nine-color decoding from the signal output from the image sensor 3.

The red (R) and blue (B) color signals are each sent to a gain control circuit 5.
6, the signal is combined with a luminance (Y) signal in a matrix circuit 7 to generate a color difference signal (R-Y, B-y). The hindlimb brightness and color difference signals are divided into two paths, one is output as a TV signal by the encoder 8, and the other is controlled by the white balance control system.The control system uses the brightness and color difference signals mentioned above to take pictures. Detects the white area on the screen,
Generates a signal for adjusting white balance, the R
, B is retained in the gain control circuit 5.6 in the signal path. The operation of the control system in this embodiment will be explained in detail below. Color difference signals (R-Y,
B−Y) are added and subtracted at a predetermined ratio (for example, 1:1) to obtain R−B and R+B−2Y signals. By the way, the locus of color temperature change (color quality change of natural light) according to black body radiation is expressed on the color difference plane at the position shown in FIG. 5, and the relationship with the R-B, R+B-2Y axis is as shown in the figure. That's right. In other words, white (R-Y
, the intersection of the B-Y axes), and the deviation from white due to reasons other than color temperature changes can be determined at R+B-2Y. The white detection circuit 13 generates a control signal for determining whether or not it is effective for white balance control from the above two types of signals and the luminance signal, and for extracting only the portion of the signal that is deemed to be effective. Incidentally, the luminance signal is, for example, the R-B
.

The amplitude is so small that it cannot be detected by the R+B-2Y signal (
works to remove chromatic signals in dark) areas. The signal generated by the white detection circuit 15 is R-%l R+
The gate circuits 11 and 111 arranged in the s-2x signal path are driven, and only the signal obtained from the white portion of each signal is sent to the next integrating circuits 12 and 112. Each signal averaged over the entire screen (or several screens) at 112 is compared with a reference voltage corresponding to a white balance (hereinafter abbreviated as WB) reference point at the next comparison amplifier circuit 14, 114 to generate a WBflllJX] signal. In this example, the control signal in the R-B axis direction output from the amplifier circuit 14 and the control signal in the R+B-2Y axis direction output from the amplifier circuit 114 are red (R
).

The blue (B) signal is converted to a signal for gain control. (For example, if the above R-B and R+B-2Y are used only for white detection and the WB control signal is generated from R-Y and BY, the WB tracking 17 becomes unnecessary.) 17 is an adder as shown in FIG. 4, for example;
It consists of a subtracter, a coefficient unit (if necessary), etc.

The present embodiment also includes a fluorescent light detection circuit 19 for determining whether the illumination is a fluorescent light from the output of a photodiode 18 provided in the camera body, and an aperture detection circuit 16 for detecting the state of the aperture 2. ing. Only when the fluorescent light detection circuit 19 determines that the illumination is a fluorescent light, the gate 111 in the R+B-2Y signal path becomes conductive, and the R+B-2 signal path becomes conductive.
Control is performed in the Y-axis direction (G-Mg direction). Conversely, if it is determined that the illumination is not a fluorescent light, the gate 111 is shut off and 01Mg control is no longer performed. In other words, sunlight, incandescent light, etc. are located on the color temperature change locus mentioned above, and it is possible to obtain WB by controlling only the R-B axis direction, and by limiting the control direction in this way, it is possible to obtain a light green color. Unnecessary malfunctions caused by objects such as the camera can be avoided. A correction circuit 15 provided between the comparison amplifier circuit 14 and the WB tracking 17 adjusts lighting conditions (indoors, outdoors, fluorescent lights, incandescent lights, etc.) based on signals from the fluorescent light detection circuit 19 and the aperture detection circuit 16. The WB control signal is corrected based on the discrimination result. When the aperture 2 is stopped down to a predetermined value (for example, F4) or more, it is determined that the illuminance is sufficiently high, that is, it is outdoors on a clear day, and in such a case, the color temperature is generally high (
50 and 0), the WB reference point is shifted to the high color temperature side and the control for the low color temperature side is reduced. On the other hand, if the aperture 2 is set at a predetermined value or more, it is determined that the illuminance is low, that is, indoors, and if it is not a fluorescent light, it is assumed that the illuminance is a low color temperature lighting (below 3000°) such as an incandescent light. Therefore, the WB reference point is shifted to the lower color temperature side, and control on the higher color temperature side is limited. This correction circuit 15 is configured as shown in FIG.
(within the dotted line), and the Cont terminal H1 emphasizes the high color temperature side, L
At o, control characteristics that emphasize the low color temperature side can be obtained. According to this embodiment, since the WB control means is applied in accordance with the lighting situation, the operation is reduced even in the case of a subject with few white parts that are effective for WB adjustment.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, instead of the correction circuit 15 added to the output of the comparison amplifier circuit 14 of the first embodiment, the WB reference point is shifted by changing the comparison reference voltage of the amplifier circuit 14. It is something. Five types of reference voltages, V1 for low color temperature, V3 for high color temperature, and V2 for others, are connected to one terminal of the comparison amplifier circuit 14 through a selection means 20 such as a multiplexer, and the voltages are varied depending on the type of lighting. be selected as appropriate.

This embodiment also has the same effects as the first embodiment.

Next, a fifth embodiment of the present invention will be described with reference to FIG. The configuration of this embodiment is similar to the first embodiment,
For the sake of simplicity, the R+B-2Y axis control system and white portion detection system will be omitted. The feature of this embodiment is that the information for controlling the WB control signal correction circuit 15 before WB adjustment (R, B
It is obtained from the R and B signals of the gain control circuit.

The illumination light discrimination means 21 generates a signal for controlling the WB control signal correction circuit 15 corresponding to the output of the aperture detection circuit 16 from the R, B signals and the white part extraction signal. The correction circuit 15 obtains the output signal of the illumination light discriminating means 21 (and a fluorescent lamp discriminating signal may be added thereto as in the first embodiment, although not shown), and performs the same correction as in the first embodiment. Applied to control signals.

The fifth embodiment of the same book and the first embodiment may be combined. Further, instead of the correction circuit 15, a comparison reference voltage selection means as in the second embodiment may be used.

Next, a fourth embodiment of the present invention will be described with reference to FIG. Also in FIG. 7, the control system in the R1B-2Y axis direction, the white part detection system, etc. are omitted. The overall configuration is also similar to the first and fifth embodiments. In this embodiment, there is a light diffusing plate 25, a red light transmission filter 23, a blue light transmission filter 24, and a pair of photodiodes 118 attached to the camera body. The R/B ratio of ambient light is detected by an external light colorimetry system consisting of a division circuit 22 connected to the photodiode. The illumination light discrimination means 21 generates a signal for controlling the WB control signal correction circuit 15 based on the R/B ratio. The operations of the correction circuits and the like other than those described above are the same as those in the first and third embodiments, so a description thereof will be omitted. In this embodiment, as in the third embodiment, the comparison reference voltage input to the comparison amplifier circuit 14 may be switched instead of the correction circuit 15, and a combination with the first embodiment is also possible. be. Furthermore, in the fourth embodiment, the photodiode 118
It is also possible to use 11 detection and 0 for fluorescent lamp detection.

The fourth and fifth embodiments have the same effects as the first embodiment, but they allow for more detailed classification of illumination light (e.g. cloudy outdoors and extremely bright indoors). Become.

Next, a fifth embodiment of the present invention will be described with reference to FIG. This example is based on the first example. A WB control signal holding means 50 is provided at a location corresponding to the WB control signal correction circuit 15 in the second and third embodiments. The operation will be explained below. The zoom detection means 32 detects whether the electric zoom switch 54 or the zoom lens moving mechanism 53 has been manually operated to move the zoom lens 101 during photographing. ) outputs a detection signal. The output zoom operation start signal (a terminal output)
In response, the holding means 30 provided at the output stage of the comparison amplifier circuit 14 for generating the WB control signal holds the output value of the amplifier circuit 14 at that time, and holds the output value of the amplifier circuit 14 at that time until the reset signal is input from the terminal C. The held value is supplied to the next stage of WB tracking. Therefore, while the holding means 30 is operating, the WB adjustment is stopped, and there is no change in color tone during the zoom operation. When the zoom operation is stopped, a zoom operation end signal is output from the terminal of the zoom detection means 32. Upon receiving the termination signal, the reset determination circuit 51 compares the output value of the comparison amplifier circuit 14 and the output value of the hold means 50 at that time in synchronization with the termination signal, and if the difference between the two is small, (For example, the difference between the two is 10 to 1% with respect to the WB control dynamic range.) In other words, if it is determined that there will be no significant change in color tone even if the hold is released, the terminal of the hold means 30. Provides heliset signal. Upon receiving the reset signal, the holding means 50 releases the hold and supplies the output of the comparison amplifier circuit 14 to the next-stage WB racking 17 as a WB control voltage. According to this embodiment, unstable color tone changes caused by zooming operations can be prevented, and this is particularly effective in preventing malfunctions when changing from long to close-up. Further, the zoom detection may be performed in combination with not only optical zoom but also electronic zoom means.

Next, a sixth embodiment of the present invention will be described with reference to FIG. Since the overall configuration is similar to the first embodiment, description of individual functions will be omitted. The white detection circuit 13 operates on the same principle as in the first embodiment and outputs a signal for extracting a white part in synchronization with the white part on the screen. The white part extraction signal is R
-B (and R+B-2Y although not shown) is supplied to the gate circuit 11 in the signal path. In this embodiment, a white ratio detection circuit 35 is provided which detects the ratio of the white part occupying the screen based on the white part extraction signal. When the ratio of the white part in the screen is below a predetermined amount (for example, 10 to 20%) and it is expected that appropriate WB control will become difficult, the circuit outputs the output value of the comparison amplifier circuit 14 for WB control signal generation. The holding means 50 is controlled to hold. The hold circuit 50 supplies the control signal held while the white portion ratio is below a predetermined amount to the next stage WB tracking 17, and detects when the white portion ratio exceeds the predetermined amount by the white ratio detection circuit 35. When the determination is made, the hold is released and normal WB control is resumed. Release the hold and
The WB control signal may be temporarily reset to an intermediate value when performing normal control.

Further, in the main unit 6 and the fifth embodiment, the holding means is provided at the output stage of the comparison amplifier circuit 14, but this is provided at the output stage of the racking 17 at the input (integrator circuit 12) output or WB of the amplifier circuit. It's okay. This embodiment is effective in preventing WB control from becoming unstable and malfunctioning due to a decrease in the white area during panning, etc., making it more susceptible to the influence of other chromatic areas.

〔Effect of the invention〕

According to the present invention, the control method (one-dimensional, two-dimensional) and control characteristics (emphasis on high color temperature, etc.) that are adapted to the illuminance and type of light source are selected, which is effective in preventing malfunctions and improving WB accuracy. be.

In addition, unnecessary tracking can be suppressed due to changes in the shooting situation due to zooming, panning, etc., preventing malfunctions and color % (W
It is effective in stabilizing B).

[Brief explanation of drawings]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 (h) and (b) are circuit diagrams and operating characteristic diagrams showing a specific example of the correction circuit shown in Fig. 1, and Fig. 5 shows the operation. A color difference plan view for explaining the principle, FIGS. 4 and 5 are configuration diagrams showing specific examples of the main blocks in FIG. 1, and FIGS. 6 to 9 are block diagrams showing other embodiments of the present invention, respectively. It is. 11.111...Gate circuit 13...White detection circuit 15...Correction circuit 16...Aperture detection circuit 17...WB) Racking 21...Illumination light discrimination means 60...Holding means 51 . . . Reset discrimination circuit 32 . . . Zoom detection means 55 . . . White ratio detection circuit. No. 1 B No. 20 Agent Patent Attorney Katsuo Ogawa 7. Kyounu-Y No. 1! 4. Comparison 1 21. θFIIMW41 25.

Claims (1)

[Claims] 1. Color signal gain control circuit (5, 6) and integration circuit (12, 112) for generating a white balance control signal
and a comparison amplifier circuit (14, 114), and a tracking correction means (14, 114) that drives a color signal gain control circuit using the control signal.
17), an aperture detection means for detecting the aperture value of the aperture mechanism (2) in a white balance adjustment circuit consisting of a white detection means (13) for extracting a signal of a white part in the photographic screen, and a gate circuit (11, 111). (16
), a fluorescent light detection means (19) for detecting whether the light is a fluorescent light based on the blinking cycle of the light, etc., and a correction means (15) for appropriately correcting the white balance control signal based on the detection results of the aperture and the fluorescent light detection means.
) A white balance control device characterized by having: 2. Based on the results of the two detection means (16, 119), the type of lighting such as outdoor sunny weather, outdoor cloudy weather, indoor incandescent lamp, indoor fluorescent lamp, etc. and shooting conditions are determined, and the white balance is adjusted according to the situation. The white balance control device according to claim 1, wherein the white balance control device switches to an adjustment method. 3. The white balance control device according to claim 1, wherein the correction means (15) comprises means for performing voltage shift, change range limitation, etc. on the control signal. 4. The voltage shift is set to a higher color temperature when the discrimination result is outdoors, to a lower color temperature when the result is indoor incandescent light, and to a lower color temperature when the discrimination result is indoor fluorescent light. 2. The white balance control device according to claim 1, wherein the white balance control device operates to a setting that is approximately intermediate between two types of settings. 5. The change range limitation is performed by limiting the amount of change in the white balance control signal, and widens or narrows the follow-up range of white balance adjustment for color temperature changes. A claim characterized in that, only when a fluorescent lamp is detected, a white balance adjustment is also performed in response to a change in color quality of the light source other than a change in color temperature, and the adjustment is stopped or the range is narrowed at times other than when a fluorescent lamp is detected. Item 1. White balance control device according to item 1. 6. In the white balance control device, one of the plurality of reference power supplies (V_1 to V_3) is selected by the selection means (20) controlled by the outputs of the aperture detection means (16) and the fluorescent lamp detection means (19). is selected, and the voltage from the selected power supply is applied to the comparison amplifier circuit for generating the white balance control signal (
14) The white balance control device according to claim 1, wherein the white balance control device is configured to be supplied to the white balance control device according to claim 1. 7. In the white balance adjustment circuit, a means (21) for detecting the color temperature of the light source from the red (R) and blue (B) signals obtained from the white portion before gain control is provided, and the control signal correction means ( 15) The white balance control device according to claim 1, wherein the white balance control device is configured to control. 8. In the white balance adjustment circuit, a light diffusing plate (25), a red filter (23), a blue filter (24)
), a photodiode (118), and a divider (22). The white balance control device according to claim 1, characterized in that it is configured as follows. 9. In the white balance adjustment circuit, means (32) for detecting a zoom operation and means (32) for holding the white balance control signal are provided.
0) and means (31) for determining whether to continue or release the hold. 10. In the white balance control device, the hold means includes a comparison amplifier circuit (14) for generating a white balance control signal.
10. The white balance control device according to claim 9, wherein the white balance control device is configured to hold the input signal of . 11. In the white balance control device, means (35) for detecting the white ratio in the screen based on the output of the white color detection means (15).
10. The white balance control device according to claim 9, further comprising: a device configured to hold the control signal for a period when the ratio of the white portion is lower than a predetermined value when the ratio of the white portion is lower than a predetermined value. 12. A white balance control device characterized in that, in the white balance adjustment circuit, illuminance of the subject is used as color temperature detection information. 13. A white balance control device characterized in that the white balance adjustment circuit does not detect a signal of a low brightness portion of the subject.