JPS63302687A - White balance device - Google Patents

Abstract

PURPOSE:To remove only a color signal exceeding a saturation level and to prevent a malfunction by stopping an input signal to an integrating means in a time interval in which the level value of the color signal exceeds a prescribed level. CONSTITUTION:G, R, B signals are integrated during one field for reading a charge from an image pickup element in field integrating holding circuits 16, 17, 18, inputted to a removing and digital sample hold circuit 20 to maintain the ratio of R/G, B/G, at the time of a still photographing, the gain of the G, R, B signals is controlled by an open control output circuit 30 and at the time of a movie photographing, it is controlled by a feed back control output circuit and a gain control amplifier 4 and during the time interval in which the one signal level of the G, R, B signals exceeds the prescribed level the signal input to the field integrating and holding circuits 16, 17, 18 is stopped by a high level cut circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance device, and more particularly, to a white balance device used in a color imaging device such as an electronic camera.

[Prior Art] As a white balance device in a conventional color video camera, etc., the output of a photoelectric conversion element is filtered through a low-pass filter (hereinafter referred to as LPF) for the three primary color lights of R (red), G (green), and B (blue). ) to the arithmetic circuit,
There was a color signal gain control amplifier (hereinafter abbreviated as OCA) in a video signal system using the same arithmetic circuit to adjust the ratio of color signals R, G, and B to 1:1:1. The LPF is used here to prevent noise at frequencies higher than the signal and to stabilize the signal by removing ripple components contained in the light. A delay transmission system consisting of a capacitor and a capacitor, and has a delay time between an input signal and an output signal.

Therefore, a white balance device having such an LPF is not suitable for devices that require high-speed response, such as electronic still cameras.

In addition, as another white balance device, the output of the OCA is fed back and inputted to a comparison control circuit, and the comparison control circuit compares the output of the reference signal generation circuit and guides these errors to the OCA, reducing errors. OCA in the direction of becoming
was under control. However, even in this white balance device, it is generally necessary to provide an LPF to average the video signal over several fields.
Furthermore, since this device is a feedback system, its responsiveness is poor, making it even less suitable for electronic still cameras.

[Problems to be Solved by the Invention] Therefore, the applicant first integrated each of the RlG and B color output signals of the photoelectric conversion element for a predetermined time using an integrating means, and then performed calculations based on these integrated outputs. Japanese Patent Application No. 62-04830 describes a white balance device that controls the gain of each color signal in GCA by performing
Proposed by No. 2. This white balance device performs appropriate white balance adjustment for the actual shooting light used, and since the circuit does not include any delay elements, it provides gain control with good responsiveness that is especially suitable for electronic still cameras. It will be done.

However, in this case, if the level of the color signal reaches a saturation level that exceeds the dynamic range of the imaging means before the integrating means, even the signal at such a saturation level is time-integrated by the integrating means, and this integral If the gain of the color signal is controlled by the output, there is a risk that the device will malfunction.

Conventionally, when there is a risk of malfunction in an auto white balance device, it has been dealt with by presetting means, similar to when using a strobe. However, in this case, it is difficult to determine the criteria for equipment malfunction, and there is a risk of malfunction.
If you switch to a preset method for this purpose, you will end up shooting with a preset in most cases, and the auto white balance will lose its meaning. At the same time, switching to the preset state is not preferable because information about external light (subject light) will be completely ignored.

In view of these problems, the present invention has excellent responsiveness and, moreover, eliminates only the color signal exceeding the saturation level without switching to a preset state when the color signal exceeds the dynamic range of the imaging means. The purpose of the present invention is to provide a good white balance device that does not malfunction.

Means and operation for solving problem E] The white balance device of the present invention obtains each time integral value regarding a plurality of color signals from an integrating means, and calculates the time integral value regarding the plurality of color signals based on the output of the integrating means. Control gain.

When the level of at least one of the plurality of color signals exceeds a predetermined level, signal input to the integrating means is stopped for that time period.

[Embodiment] FIG. 1 is a block diagram of a white balance device showing an embodiment of the present invention.

The white balance device shown in FIG. 1 is applied to an electronic camera capable of still photography and movie photography. An image sensor (not shown) of this electronic camera is also used as a photometric (il 1 color) sensor for white balance control of this white balance device. From this imaging cable, R and B signals of the color video signal are alternately transmitted line-sequentially to the video processing circuit 3 through line 1, and G signal is transmitted through line 2. In the video processing circuit 3, a GCA 4 is inserted in line 1 of the above line sequence for white balance adjustment.

This GCA 4 includes two OCAs that are each independently controlled by two systems of control signals sent from a control line 48, which will be described later, so that the gains of the R signal and B signal are set respectively. The R and B color signals on the output lines 5 and the color signals on the lines 2 and 6 of the GCA 4 are sent as video signals to the next stage circuit, and at the same time are used as control information for gain control of the GCA 4. In other words, by controlling the gain of GCA4 with this white balance device, R, B,
The G color signal level is 1:1:1.

A buffer circuit 8 is connected to the G signal line 2,
A buffer circuit 9 is connected to the R/B signal line 5 on the output side of the GCA 4. The output terminal of the buffer circuit 8 is connected to a high level cut circuit 10 switch 11,
The output terminal of the buffer circuit 9 is a high level cut circuit 10
It is connected to the switch 12 of. The high level cut circuit 10 is a circuit that cuts the transmission of the color video signals when the levels of the G and R/B signals reach approximately the saturation level, and is connected to the switches 11, 12 . It consists of a variable resistor 13 and a comparator 14. In other words, the dynamic range of the image sensor has a limit, so when the image sensor receives a high-brightness image, the high-brightness component of the color video signal becomes saturated. A high level cut circuit 10 is used to prevent the signal from being integrated.

This high level cut circuit 10 compares the output of the buffer circuit 8, that is, the level of the G signal, with a reference level set by a variable resistor 13, and when the level of the G signal exceeds the reference level, the output of the comparator 14 causes a switch 11 to
．． 12 from the on state to the off state, the buffer circuit 8
．． The output of 9 is cut off from being sent to the subsequent stage. Switch 11.12 by detecting the level of the G signal
The reason for controlling this is that when imaging a high-brightness subject with a normal light distribution, the RlB and G color video signals output from the image sensor do not uniformly reach the saturation level, but in many cases first. This is because the components of the G signal reach the saturation level. The output terminal of switch U is connected to field integral holding circuit 16, and the output terminal of switch 12 is connected to R/
Field integral holding circuit 1 via B signal separation circuit 15
Connected to 7°18.

The field integral holding circuit 16 integrates the G signal over the effective scanning period of one field and holds it. The signal and the B signal are similarly integrated over the period of one field and held. Field integration and hold circuits 16, 17 and 18 are connected to a division and digital sample and hold circuit 20 at the subsequent stage.

The division/digital sample hold circuit 20 has R, B
Field integral holding circuit 17 for each color signal.
18 during the vertical blanking period, and divides it by the output of the field integration holding circuit 16 regarding the G color signal to obtain and hold the respective ratios R/G and B/G. This division/digital sample and hold circuit 20 is provided with a dual type current addition type D/A converter 21. Two D/A converters 22.2 in this D/A converter 21
3 converts the count values of the self-running counter 24 connected to this D/A converter 21 into analog values. The D/A converter 22 is related to the R signal, and the D/A converter 22 is related to the R signal.
The A converter 23 is related to the B signal. A changeover switch 25 is connected to the reference input terminal ref of the D/A converter 21 for switching between the output of the field integration holding circuit 16 and the reference voltage V ret of the reference voltage generation circuit 26 in response to a changeover signal Sl. Latch input terminal 1 a t of division/digital sample hold circuit 20
The output terminal of the comparator 27 is connected to ch. Both input terminals of the comparator 27 are supplied with a switching signal S2.
A selector switch 28, 29 which can be switched by is connected. The changeover switch 28 is used to change over the outputs of the field integral holding circuits 17 and 18 and input it to one input terminal of the comparator 27.
Reference numeral 9 switches the outputs of the D/A converters 22 and 23 and inputs them to the other input terminal of the comparator 27.

Further, the D/A converter 21 to which the switching signal S2 is applied
The input selection terminal sel selects the digital input from the self-running counter 24 and the latch signal, which is the output of the comparator 27 inputted from the latch input terminal 1atch, into the R signal system and the B signal system, respectively, in synchronization with the switching signal S2. This is for distributing the data to the corresponding D/A converters 22 and 23. Note that the output of the unselected D/A converter is held at the last state when it was selected.

As the output stage of the division/digital sample and hold circuit 20, an open control output circuit 30 and a feedback control output circuit 34 are provided.

The oven control output circuit 30 is a circuit used during still photography, and includes inverting amplifiers 31 and 32 that amplify the outputs of the D/A converters 22 and 23, respectively, and an output selection circuit 46 that outputs the outputs of the inverting amplifiers 31 and 32. It consists of an output line 33 that sends to.

The feedback control output circuit 34 is a circuit used during movie shooting, and converts the outputs of the D/A converters 22 and 23 into reference voltages V re of variable resistors 35 and 36, respectively.
rl, differential amplifier compared with V rer2 37.38
A low pass filter (hereinafter abbreviated as LPF) 39.40 is connected to the output side of the differential amplifier 37.38 for system stability, and the output of this LPF 39.40 is sent to the output selection circuit 46. It consists of an output line 41.

Further, a preset output circuit 42 is provided for presetting the gain of the GCA 4 to a known value, and the preset output circuit 42 is connected to the reference voltage Vrer3. Vref
4 (In the preset suitable for strobe light, the reference voltage Vr
ef3', Vrer4') to adjust the RlB color signal gain, and a reference voltage V set by this variable resistor 43.44.
ref3. Vref4 (Vref3'.

It consists of an output line 45 that sends the level of Vref4') to an output selection circuit 46.

The output selection circuit 46 is provided with a selection switch 47, and a contact terminal 47a of the switch 47.

47b and 47C are respectively connected to the above output lines 45°33.
41 is connected, and a contact terminal 47d, which is switched by the switching signal S3 and connected to any one of the contact terminals 47a, 47b, and 47c, is connected to a gain control terminal of the GCA 4 by a control line 48. Switching signals SL, S2. S
3 is generated by the timing control circuit 49.

Note that the output lines 33, 41, 45 . Output selection circuit 46 and selection switch 47 (47a
, 47b, 47c, 47d), and the control line 48 is a two-system parallel (independent) system, which is shown in a simplified state in FIG.

Now, the general configuration of the entire system of an electronic camera to which the above white balance device is applied will be explained with reference to FIG. It is controlled by sending and receiving signals between the The system controller 52 outputs the switching signal S
1. It has a function of a timing control circuit 49 that generates S2.83, etc., a photometric information processing function, and the like. The exposure control bag W151 includes control circuits for a strobe, an aperture, a shutter, and the like.

The input terminal of the system controller 52 includes a strobe selection switch 53. A still/movie selection switch 54 and a photometric sensor 55 are connected. For example, when a strobe is used, the strobe selection switch 53 is turned on, and the input terminal, which is set to H by the pull-up resistor 56 when the strobe is not used, becomes "Lo" at this time. Further, the still/movie selection switch 54 is, for example, turned off during still shooting to set the input terminal of the system controller 52 to "Ho" by the pull-up resistor 57, and turned on during movie shooting to set the input terminal to 1L. Furthermore, in this example,
The photometric sensor 55 for exposure control is a well-known sensor disposed at an appropriate position on the camera independently of the image sensor, but of course the image sensor can also be used as the photometric sensor 55 for exposure control. It may be something.

Next, the operation of the above white balance device will be explained. An image signal whose gain is to be controlled based on the output of the image sensor is supplied to line 1.2. As shown in FIG. 3, this image signal has a field period fl.

f2. Vertical blanking period B between each signal of f8...
l, B2. It has BS...

First, the case of still photography will be explained. In the case of still photography, the output contact terminal 47d of the selection switch 47 of the output selection circuit 46 is initially connected to the preset contact terminal 47.
connected to a. Therefore, the output line 45 of the preset output circuit 42 is connected to the control line 48, and the preset voltage Vref3.
Vref'4 is input to the gain control terminal of GCA4. Thereby, the GCA 4 is controlled to a reference gain for white balance in still photography. Thereafter, when the shutter button is pressed, the shutter opens within the first field period fL and exposure for white balance is performed. When the exposure is completed, a video signal corresponding to the exposure amount is read out from the image sensor in the next field period f2, so R and B signals are input to line 1.
A G signal is input to line 2. During this read field period f2, the reference value preset by the preset output circuit 42 is given as the gain control signal of the GCA 4. Then, the field period f2 of this readout
The video signals of lines 2, .
5 to the buffer circuit 8.9. The G signal that has passed through the buffer circuit 8 is input to the field integral holding circuit 16 via the switch 11 of the high level cut circuit 10, and the R and B signals that have passed through the buffer circuit 9 are input to the switch 12 of the high level cut circuit 10. After passing through the R/B signal separation path 15, the signals are separated and input to field integral holding circuits 17 and 18, respectively.

The field integration holding circuits 16, 17, and 18 integrate the G, R, and B signals, respectively, over one field period f2 of charge readout from the image sensor, but the subject light is very strong and the dynamic of the image sensor When the G signal level rises to a saturation level corresponding to the upper limit of the range, this high brightness range is cut off by the high level cut circuit 10 and only the effective component is integrated.

G, R integrated over one field period.

At the end of the field period f2, the B signal is held in level and input to the division/digital sample and hold circuit 20. Then, the division/digital sample and hold circuit 20 operates during the vertical blanking period B2 following the field period f2. The changeover switch 25 is activated by the start changeover signal Sl as shown in the figure.
The G signal integrated over one field period is input to the reference input terminal ref of the D/A converter 21. In addition, the changeover switch 28
．． 29 is alternately switched to either the R or B signal side in synchronization with the switching signal S2.

That is, in the state shown in FIG. 1, the R signal side is selected by the switching signal S2, and the output of the field integration holding circuit 17 and the output of the D/A converter 22 are compared by the comparator 27. When the D/A converter 22 starts D/A converting the output of the self-running counter 24 in response to the switching signal S2 input to the input selection terminal sel, the output of the D/Am converter 22 is converted to a comparator via the changeover switch 29. 27 and is compared with the output of the field integration holding circuit 17.

Then, when the output level of the D/Aa converter 22 matches the output level of the field integral holding circuit 17, the output of the comparator 27 is sent to the latch input terminal 1atch,
The analog value of the D/A converter 22 is latched. The analog value of the D/A converter 22 at this time is equal to the output signal R of the field integral holding circuit 17.

After the D/A conversion by the D/A converter 22 is completed, the B signal side is selected by the switching signal S2 in the second half of the same vertical blanking period B2, and the output of the field integral holding circuit 18 and the D/A conversion are The output of the D/A converter 23 is compared with the output of the D/A converter 23 by the comparator 27, and when the re-inputs of the comparator 27 match, the analog value of the D/A converter 23 is latched. The analog value of the D/A converter 23 at this time is equal to the output signal B of the field integral holding circuit 18. When the D/A conversion by the dual/A converters 22 and 23 is completed, the changeover switch 25 is switched to the reference voltage generation circuit 2 by the changeover signal S1 at the end of this vertical blanking period B2.
6 and the reference voltage V ref is switched to the output side of D/
It is input to the reference input terminal ref of the A converter 21.

Then, the ratio Vrer/of the reference input voltages switched to the analog values R and B of the D/A converters 22 and 23, respectively.
Since G is multiplied as a coefficient, the output of the D/A converter 22 is held at VrOrXR/G, and the output of the D/A converter 23 is held at VrefXB/G.

Then, when the vertical blanking period B2 ends and the next field period f3 starts, the output contact terminal 47d of the selection switch 47 of the output selection circuit 46 changes to the open control contact terminal at the start of the next field period f3. Since the connection is switched to 47b, the D/A converter 2
The outputs of 2.23 are amplified by inverting amplifiers 31.32 of the open control output circuit 30, respectively, and the outputs of the output lines 3
3 through a control line 48 to the gain control terminal of the GCA 4. Therefore, after the field period f3, the gain control that provides the optimal white balance for the still image photographed within the first field period fl is GCA.
This will be done in 4.

Note that when a strobe light is used in still photography, the open control as described above is unnecessary because strobe light has fixed spectral characteristics unlike daylight. Therefore, in this case, the output contact terminal 47d of the changeover switch 47 is connected to the preset contact terminal 47a by the switching signal S3. In this case, the output contact terminal 47d is opened midway through the open control contact terminal 47b.
Exposure to strobe light is performed without switching the connection to the digital camera set contact terminal 47a, and the data taken out from the image sensor 55 is transferred to the GCA 4.
variable resistor 4 of the preset output circuit 42.
The reference voltages Vrcf'3' and Vrcl'4' suitable for the strobe light set in 3.44 are applied to the gain control terminal of the GCA 4, and white balance control suitable for the strobe light is performed. Therefore, in this white balance device, the preset output circuit 42 has a simple configuration, serving both as a preset circuit for providing a reference value for open loop control and as a strobe preset circuit. It should be noted that the "preset mode" during strobe lighting also includes so-called auto preset.

Also, instead of providing the preset output circuit 42,
It is also possible to use the preset function of the self-propelled counter 24 and cause the D/A converter 21 to generate a preset signal.

By the way, regarding only the open control used during still photography, the data for white balance control may be taken out from the input terminal of the GCA 4, in which case the G
Although the reference value control of CA4 (connecting the terminal 47d of the output selection circuit 46 to the terminal 47a during the field period f2) is no longer necessary, in this white balance device, for convenience, it is also used for feedback control during movie shooting, which will be described below. From there, data is extracted from the output side of GCA4.

Next, the case of movie shooting will be explained. In the case of movie shooting, the contact terminal 4 of the selection switch 47 of the output selection circuit 46
7d is contact terminal 4? c, the output line 41 of the feedback control output circuit 34 is connected to the control line 4.
Connected to 8.

In this case, the G signal data taken out from line 2 for white balance control and the R and B signal data taken out from line 5 on the output side of GCA 4 are each buffered as in the case of still photography. After passing through the circuit 8.9, the high brightness level is removed by the high level cut circuit 10, and the R and B signals are separated by the R/B signal separation circuit 15. Each of the G, R, and B signals is integrated for one field period and guided to the division/digital sample/hold circuit 20, where the above-mentioned division operation is performed during the vertical blanking period. Then, from the D/A converter 22.23 (Vref' xR/G
), (Vref xB/G) are output. This D/A
Output of converter 22.23 (Vrof xR/G),
(Vref xB/G) are input to the differential amplifiers 37 and 38 of the feedback control output circuit 34, respectively, and the reference voltages Vref1. Vref
2, differential amplification r:i37. 38 (71) comparison output (, tLPF39.40Ga passed, output line 4
1 to the gain control terminal of the GCA 4 through a control line 48. In the case of movie shooting, since the video signal is continuously output from the image processing circuit 3, the R and B signals are not preset in the OCA 4, so the output (Vref xR/G), (Vrer XB/G)
becomes a proper value in the first read field period, and this D/A conversion output (Vref XR/G)
, (Vref XB/G) and the reference voltage V er
l.

By comparing with Vref'2 and performing feedback control, V rel - V rcf2
If adjusted so that m V rat', R/G-1
, becomes B/G-1.

In FIG. 1, the output selection circuit 46 has been described as having two parallel selection switches 47 that are switched by the command of the switching signal S3, but specifically, an analog multiplexer IC is used as the output selection circuit 46, For example, "standard logic IC4053" can be applied. In this case, to explain one of the two parallel systems, its circuit diagram has the configuration shown in FIG. Both the applied switching signals S3a and S3b are “Ho”.
At this time, the analog switches 58 and 59 are both connected to one contact terminal as shown in the figure, and the signal from the feedback control contact terminal 47c is guided to the output contact terminal 47d.

In addition, when the switching signal Sea is II L l'', the switching signal S3
When b is "H2", only the analog switch 58 is connected to the other contact terminal on the opposite side from the one shown in the figure, so the signal from the oven control contact terminal 47b is guided to the output contact terminal 47d. Furthermore, the switching signal S3a
It may be "L" or "Ho" for switching signal S3.
When b is "L", the analog switch 59 is connected to the other contact terminal on the opposite side from that shown in the figure, so the signal of the preset contact terminal 47a is guided to the output contact terminal 47d.

By the way, in the above white balance device, the D/A
As the converter 21, a current addition type converter 21 is used, which is easy to achieve accuracy in principle, but when a current addition type D/A converter 21 is used, due to the characteristics of the current-voltage converter included in the output stage, There is a problem in that the output voltage is inverted with respect to the reference input voltage. Therefore, this is usually addressed by providing an inverting amplifier. However, in order to avoid complicating the circuit due to the space limitations of the electronic camera, the field integration holding circuits 16 and 17 provided at the front stage are used here.
．． By considering 18 configurations.

This problem has been resolved. That is, the field integral holding circuit 16 is of an inverting type, and the field integral holding circuits 17 and 18 are of a non-inverting type. Alternatively, when the field integral holding circuit 16 is of an inverting type, the field integral holding circuits 17 and 18 may be of a J-to inverting type.

Therefore, next, the above-mentioned field integral holding circuit 16°17.
18 specific circuit configurations, for example, G
The field integral holding circuit 16 for signals has an inverting type configuration as shown in FIG. 5, and the field integral holding circuits 17 and 18 for R and B signals have a non-inverting type configuration as shown in FIG. Ru.

In FIG. 5, the field integral holding circuit 16 includes a hold switch 61 . Resistance 62, 63. Operational amplifier 64.
It is composed of an integrating capacitor 65 and a reset switch 66. When the hold switch 61 connected between the input terminal and ground is open, the input terminal signal Vl
n is input to the inverting input terminal of the operational amplifier 64 through the resistor 62. A parallel circuit of an integrating capacitor 65 and a reset switch 66 is connected between the inverting input terminal and the output terminal of the operational amplifier 64.
When the inverting input terminal of the operational amplifier 64 is open, a signal charge inputted to the inverting input terminal of the operational amplifier 64 is accumulated in the integrating capacitor 65, and an integrated voltage V out is outputted to the output terminal of the operational amplifier 64. Such a circuit configuration is generally well-known as an integrating circuit, and in equation (1), R is the resistance 6.
2 and C is the capacitance of the integrating capacitor 65. The integration start time t1 is the timing tR when the reset switch 66 is opened and reset for a short time by the reset signal Rs.
The integration end point t2 is equal to the timing tH at which the hold switch 61 is closed and held by the hold signal Hd.

In contrast to such field integral holding circuit 16, field integral holding circuit 17. l'8, as shown in FIG. 6, is a hold switch 71. Resistor 72°73, operational amplifier 74. The resistor 7 has a resistance value of R and has an integral capacitor 75 and a reset switch 76 in substantially the same configuration, but one end is connected to the inverting input terminal of the operational amplifier 74.
The other end of the resistor 73 is connected to the non-inverting input terminal of the operational amplifier 74, and the other end of the resistor 73 is connected to the input terminal to which the signal Vin is applied, and is grounded via the hold switch 71. The difference is that

A non-inverting type integrating circuit configured such that the input signal Vin is input to the non-inverting input terminal of the operational amplifier 74 is generally not used as an integrating circuit. That is, the integrated voltage V obtained by the integrating circuit shown in FIG.
out' is expressed as in the following equation (2).

During operation, the integral voltage Vout' is always added as a bias to the input signal Vin, so in order to use it as a non-inverting integration circuit, the input signal Vin added as a bias must be removed. For example, it is not possible to accurately obtain an integrated voltage that changes over time.

However, in this white balance device, it is used as the field integral holding circuit 17 and 18, and the above (2)
) The integral voltage Vout' during the integral operation shown in the equation is not considered as a problem. When the hold switch 71 is closed at the timing t2-tll by the hold signal Hd at the end of the integration, the input terminal is grounded at this point and the input signal Vln becomes the ground level, so at the held timing tll, the above ( The integral voltage Vout' in equation 2) is as follows.

In this way, the integrated voltage at the time when the integration for one field period is completed and held is the fifth value expressed by the above equation (1).
The inversion type circuit shown in the figure is the field integral holding circuit 1.
6, and the non-inverting type circuit shown in FIG. The configuration in combination with the current addition type D/A converter 21 can be easily configured.

FIG. 7 shows a modification of the high level cut circuit 10. The circuit of the embodiment device shown in Fig. 1 above employs a line sequential system, but in Fig. 7, the G, R, and B signals from the image sensor are read out on independent lines. ing. In this high level cut circuit 80, the read G, R, and B signals are compared with the reference level of the variable resistor 81 by comparators 82G, 82R, and 82B, respectively. Since the reference level of the variable resistor 81 is set below the saturation level of the image sensor, all outputs of the comparators 82G, 82R, and 82B are normally "L".
It has become o. For this reason, G, R.

A switch 85G inserted into an independent line of the B signal,
The output of the three-man OR gate 84 that controls each gate of 851.85B is aL#, and the switches 85G and 851
．． 85B are both closed.

When an extremely bright subject image is captured by an image sensor, any color signal among G, R, and B signals,
However, when it exceeds the reference level of the variable resistor 81, the output of the comparator 82G, 82R, 82B corresponding to the color signal becomes "H", the output of the OR gate 84 also becomes "H", and all switches 85G , 8
5R.

85B opens to cut off the transmission of the G, R, and B color signals to the subsequent field integration holding circuit.

As mentioned above, as long as an image sensor captures a subject with a normal color distribution, among the G, R, and B color signals,
Since the G signal reaches the saturation level at the earliest point, if the circuit configuration shown in FIG. 1 is applied to the configuration of independent readout lines for the G, R, and B signals shown in FIG. 7 above, A high level cut circuit 90 shown in FIG. 8 is configured. Therefore, this high level cut circuit 90 is
Comparator 8 in the above high level cut circuit 80
2G, 82R, 82B and the OR gate 84' are simply replaced with one comparator 82.

To summarize the main components of the above-mentioned white balance device, the main components thereof are as follows: an integrating means (field integral holding means 16, 17, 18) for obtaining each time integral value regarding a plurality of color signals;
), and means (divider and digital sample hold circuit 20, open control output circuit 30.
Feedback control output circuit 34. GCA 4), and means (high level cut circuit 10) for stopping signal input to the integrating means during a time period in which the signal level of at least one of the plurality of color signals exceeds a predetermined level.

[Effects of the Invention] As described above, according to the present invention, the level value of the color signal reaches a level that exceeds the dynamic range of the elements and circuits provided in the preceding stage to obtain the same color signal, such as the imaging means. Even in such cases, malfunctions can be avoided because the signal is cut and not integrated in the section where the color signal is at such a high level.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of a white balance device showing an embodiment of the present invention, FIG. 2 is a block diagram of the entire system of an electronic camera to which the above white balance device is applied, and FIG. 4 is an electric circuit diagram showing a specific example of the output selection circuit shown in FIG. 1, and FIG. 5.6 is a waveform diagram of the color signal supplied to the white balance device. Figure 7.8 is an electrical circuit diagram showing the specific configurations of the two different types of feedback integral holding circuits in Figure 7.8. be. 4...GCA (Means for controlling gain)
10.80.90...High level cut circuit (
11.12.85G, 85R, 85B...Analog switch (means for stopping signal power) 14.82.
82G, 82R, 82B... Comparator (means for stopping signal input) 16.17.18... Field integral holding circuit (integrating means) 10... High level cut circuit (Means for stopping signal input) 20... Division and digital sample hold circuit (Means for controlling gain) 21... D/A converter (Means for controlling gain) 30... ...Open control output circuit (means for controlling gain) 34...Feedback control output circuit (means for controlling gain)

Claims (1)

[Scope of Claims] Integrating means for obtaining each time integral value for a plurality of color signals; means for controlling gains for the plurality of color signals based on the output of the integration means; A white balance device comprising: means for stopping signal input to the integrating means for a time period in which at least one signal level exceeds a predetermined level.