JPH0640668B2 - Imaging device - Google Patents

Description

The present invention relates to a white balance adjusting device in an image pickup device such as a solid-state image pickup device.

[Prior Art] Conventionally, as a solid-state imaging device, for example, a television camera, a still video camera and the like are known, and as a white balance adjustment method thereof, an automatic tracking method that operates following a change in a light source is known. ing. On the other hand, a fluorescent lamp as a light source causes flicker. Therefore, when an image is taken under a fluorescent light source, the reproduced image may be bluish or reddish. Due to the influence of the flicker, in the white balance adjustment by the automatic tracking method, if the amount of light incident on the image sensor is different from the amount of light incident on the sensor for white balance adjustment, proper white balance cannot be obtained. This situation will be further described with reference to FIG.

FIG. 1 (i) represents a change in color of a fluorescent lamp due to flicker. The top is red and the bottom is blue. On the other hand, FIGS. 1 (ii) and (iii) show the accumulation time of the CCD as the image pickup device. (ii) shows the case where the shutter speed is 1/60 second, and (iii) shows the case where the shutter speed is 1/1000 second.

As can be seen from these, in the case of (ii), the CCD accumulation time is long, and therefore the CCD output at that time, that is, the integrated output value during the accumulation period, is a value sufficiently close to the average value of (i).
In the case of (iii), since the CCD accumulation time is short, CC
The output integrated value of D may deviate significantly from the average value. On the other hand, the color measurement sensor for white balance adjustment forms the data by instantaneously measuring the color as shown in FIG. 1 (iv), for example. Sometimes. Therefore, the white balance adjustment may not be performed correctly in both the case (ii) and the case (iii).

In order to prevent this, even in the colorimetric sensor, Fig. 1 (v)
As described above, it has been conventionally proposed to use a value obtained by accumulating data for a certain period and integrating (averaging) the data. For example, considering the case of FIG. 1, if the colorimetric data for 10 ms is averaged, the effect of flicker can be removed from the output of the colorimetric sensor. Therefore, in this case, when using a low-speed shutter as in (ii), the CCD
And the average of the output of the colorimetric sensor both approach the average value of the flicker, so the error of the white balance is reduced.

However, when the high speed shutter is used as in (iii), the output value of the CCD may deviate greatly from the average value of the flicker, and thus the white balance may be largely lost.

[Purpose] An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional example, and to provide a device capable of performing correct white balance adjustment not only in a low-speed shutter but also in a high-speed shutter.

EXAMPLES The present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a first embodiment of the present invention. 1 in FIG.
Is a color temperature detection system as detection means for detecting the color temperature of the light source, 2 is an integrator as control means for integrating the detection output of the detection system 1 for a predetermined time, and 4 is imaging means for converting an optical signal into an electric signal. As an image sensor, 3 is a shutter located in front of the image sensor 4 for controlling an image capturing period, 5 is an R amplifier for amplifying a red signal output from the image sensor 4, and 6 is a B amplifier for similarly amplifying a blue signal. is there. The opening / closing signal of the shutter 3 is input to the integrator 2 whose details will be described later. Reference numeral 7 is a signal processing system thereafter.

Reference numeral 8 denotes a control voltage derivation system that derives a control voltage for controlling the gains of the R and B amplifiers 5 and 6 from the output of the integrator 2.

FIG. 3 is a concrete example of the integrator 2 and the control voltage derivation system 3, and FIG. 4 is a timing chart for explaining the operation thereof.

Further, FIGS. 1 (vi) and (vii) show the timing of integration in the low speed and high speed shutters of the present invention, respectively. The operation of the first embodiment of the present invention will be described below with reference to FIGS.

First, when the shutter 3 is closed, that is, FIG. 1 (vi)
In the period (a) (also in FIG. 4), the signal sent from the shutter 3 to the integrator 2 is at the low level as shown in FIG. 4 (i). In this case, as shown in FIG. 3, the signal from the shutter 3 (low level) and the signal obtained by delaying the signal from the shutter 3 by the delay circuit 9 are input to the NOR gate to take the NOR, and FIG. Obtain the signal (v) (that is, high level). This signal is inverted by the inverter 13 and input to the switch SW1 by the transistors (Tr) 15 and 16 via the resistor 14.

Therefore, during this period (a), the switch SW1 is turned off as shown in FIG. 4 (vi), and the signal from the color temperature detection system 1 is not transmitted to the OP amplifier 18 (via the resistor 17).

Further, the output signal of the NOR gate 12 turns on the switch SW2 by the transistors (Tr) 20 and 21 via the resistor 19 (see FIG. 4 (v
ii)), the electric charge of the capacitor 22 is discharged. Therefore, the output of the integrator 2 becomes the same potential E as that of the constant voltage source 23 as shown in FIG. 4 (viii).

Next, when the shutter 3 is opened and the exposure of the image sensor 4 is started at time B in FIG. 1 (vi) (the same applies to FIG. 4), the shutter 3 is moved as shown in FIG. 4 (i). Signal becomes high level, the output of NOR gate 12 becomes low as shown in FIG. 4 (v), switch SW1 is turned on as shown in FIG. 4 (vi),
The switch SW2 is turned off as shown in FIG. 4 (vii). As a result, the signal from the color temperature detection system 1 is the switch SW1 and the resistor 1
It flows into the capacitor 22 via 7 and the output voltage of the integrator 2 becomes the integrated value of the output of the color temperature detection system 1 as shown in FIG. 4 (viii).

If the sample-hold circuit 24 constituting the control voltage deriving system 8 is sampled by the control input "high" and held by the same input "low", the above-mentioned FIG. 1 and FIG.
Open the shutter at the time when it changes from the state of A in the figure to
NOR in the integrator 2 until the shutter is closed at the time of c
Since the output of the gate 11 is low, the sample hold circuit 24 is in the hold state during that time.

Then, when the shutter is closed at the time of FIGS. 1 and 4C, the output from the shutter 3 as one input of the NOR gate 11 is low, and FIGS. 4 (ii) and (iii)
NO by the delay circuit 9 and the inverter 10 as shown in
The other input of R-gate 11 is still low, so
As shown in FIG. 4 (iv), the output of the NOR gate 11 becomes high, the sample hold circuit 24 enters the sampling state, and the value of the output of the integrator 2 (FIG. 4 (viii)) at that time is sampled.

After that, since the output of the NOR gate 11 is high for the delay time of the delay circuit 9, the sample hold circuit 24 samples the output of the integrator 2 during that time, and then the output of the delay circuit 9 turns off, and the output of the NOR gate 11 becomes low. At that time, the sample and hold circuit 24 enters the hold state. During that time, as shown in FIG. 4 (v), the output of the NOR gate 12 remains low, so the integrator 2 continues to operate and accumulates the voltage corresponding to the opening period of the shutter 3.

Then, after a certain period of time by the delay circuit 9, the NOR gate 1
The output of 2 becomes high, switch SW1 is turned off, switch SW
2 is turned on and the output voltage of the integrator 2 is set to the constant voltage source voltage E
Return to [V] and prepare for the next integration.

The sample and hold circuit 24
Input from the R lamp 5 and the B lamp by the control voltage deriving circuit 25 constituting the control voltage deriving system 8.
A control voltage for controlling the gain of the amplifier 6 is derived, the amplifiers 5 and 6 are controlled, and white balance adjustment is performed.

Further, as shown in FIG. 1 (vii), when the high-speed shutter is used, the integration period is shortened corresponding to the shutter open period (exposure time of the image sensor), and therefore, the white balance adjustment A proper control voltage can be obtained by the control voltage derivation system 8.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6.

FIG. 5 is a block diagram of the second embodiment, in which 26 is a sampling unit for sampling the output of the color temperature detection system 1 during the open period of the shutter 3, and 27 is a value sampled by the sampling unit 26 of the shutter 3. It is an average value derivation unit that averages during the open period. Others are the same as those in FIG.

As shown in FIG. 6 (i), the output of the shutter 3 is input to the sampling unit 26 and the average value derivation unit 27, and the color temperature detection system in the sampling unit 26 and the average value derivation unit 27 is in the open state of the shutter 3. Sample the output of 1,
The sampled values are averaged. Then, when the shutter is closed (low speed shutter) and D (high speed shutter), as shown in FIG.
The control voltage derivation system 8 holds the average value derived in step 7, derives a control voltage based on the hold value, and controls the R and B amplifiers 5 and 6. By doing so as well, the output value from the color temperature detection system 1 can be given to the control voltage derivation system 8 as a value corresponding to the opening period of the shutter 3, and therefore an appropriate white balance adjustment should be performed. You can

In the above-described first and second embodiments, the signal for determining the integration and averaging period is taken in from the shutter, but this signal is, for example, an electronic signal that controls the accumulation time of the image sensor to give a shutter effect. In an image pickup apparatus to which a shutter is applied, for example, the image pickup element may be taken in at a timing corresponding to the accumulation period (image pickup period). In addition, this signal is applicable as long as it substantially matches the exposure period and timing.

[Effect] As described above, according to the present invention, the period for incorporating the color temperature detection information for white balance adjustment is made to correspond to the image pickup period of the image pickup device, so that the fluorescent lamp can be used regardless of the slow shutter speed. Appropriate white balance adjustment can be performed even when the light source such as flicker changes at a relatively high frequency.

[Brief description of drawings]

FIG. 1 shows the flicker of the light source, the exposure period of the image sensor,
FIG. 2 is a timing diagram showing the relationship between the white balance data acquisition period, FIG. 2 is a block diagram showing the first embodiment of the present invention, and FIG. 3 is an example of the integrator and control voltage derivation system of the first embodiment. FIG. 4 is a block diagram showing a circuit, FIG. 4 is a timing diagram for explaining the operation of the first embodiment, FIG. 5 is a block diagram showing a second embodiment of the present invention, and FIG. 6 is an operation of the second embodiment. FIG. 6 is a timing diagram illustrating

Claims (1)

[Claims] 1. An image pickup means for picking up a subject image, an image pickup time control means for variably controlling an image pickup time in the image pickup means, a color temperature detection means for detecting a color temperature of a light source, and a color temperature detection means for detecting the color temperature. White balance control signal forming means for forming a white balance control signal by integrating color temperature detection information of a period corresponding to the image pickup period of the image pickup means among the obtained color temperature information; An image pickup apparatus comprising: a white balance control unit that controls a white balance of the output of the image pickup unit.