JPH0732485B2 - Imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to a tracking white balance means for performing white balance depending on a component ratio of ambient light and a ratio of color signal components in an image pickup signal. The present invention relates to an image pickup apparatus having a setting white balance means for performing white balance according to.

[Prior art]

2. Description of the Related Art Conventionally, white balance is one of the basic operations of a television camera device. Thus, in a white object, the ratio of the three color signals of red (R), green (G) and blue (B) in the image pickup signal becomes 1: 1: 1.
The gain of each color signal is controlled.

In principle, this white balance is obtained by shooting a white subject, and using two color difference signals of red and blue (RY).
It is sufficient to adjust the gains of (R) and (B) during the color system process so that each of (B−Y) and (B−Y) becomes a zero level. BACKGROUND ART Conventionally, many automatic white balance devices for automatically performing white balance have been proposed for consumer or industrial television cameras. The reason for this is that it is necessary to satisfy at least the following requirements for consumer television cameras.

1. The operation method is simple or no operation is required.

2. There should be no significant image deterioration due to operation error or forgetfulness.

3. White balance with the required accuracy can be achieved under the above conditions 1 and 2.

Conventionally proposed automatic white balance apparatuses for realizing these are roughly classified into the following two types.

Tracking white balance White balance performed using the ratio of the color components in the ambient light in addition to the imaged light from the TV camera. This usually requires no manipulation by the photographer.

White balance setting White balance performed by the ratio of the color signals in the image signals of the TV camera. This is normally done by the photographer pressing the switch during that time.

The tracking white balance described above is an open loop control method that controls an image pickup signal due to information other than the image pickup signal.
Therefore, in order to obtain the required accuracy of white balance, it is necessary to reduce all the errors in each part of the system, and there is a drawback that the configuration becomes complicated in order to improve the accuracy.

In addition, the above white balance setting is based on the color difference signal (R
-Y) and (BY) are set by feedback control so that each becomes zero level, and the state is held digitally or analogly. In other words, the set white balance is closed loop control, and even if there is an error element in the system, extremely high precision white balance can be performed if it is stable with time or temperature. However, it requires an operation of pressing a setting switch for photographing a white subject.

In the set white balance, the accuracy after setting is good as described above, but the accuracy is not compensated before setting.
As a solution to this, the following attempts have heretofore been considered.

(I) Set an appropriate preset value when the power is turned on.

(II) Hold the setting value in the memory circuit even after the power is turned off.

However, even with these methods, it is hard to say that the white balance precision is sufficiently compensated for the forgetting of the setting described above.

〔Purpose〕

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an imaging device that can perform white balance with good accuracy even when an operation is mistaken or forgotten.

〔Example〕

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, a subject image is formed on the image pickup element 11 by an optical system 10 including an image pickup lens, a crystal filter, and an infrared cut filter. Image pickup signal extracted as an electric signal from the image pickup device 11
13 is made continuous by a sample hold circuit 15, and a luminance (Y) signal 17 and a red signal 19R and a green signal 19 are provided.
It is separated into three-color signal 19 of G and blue signal 19B. The luminance signal 17 is processed by the luminance processing unit 21 and then processed by the encoder.
Supplied to 23. The red signal 19R, the green signal 19G, and the blue signal 19B are processed by the red processing unit 25R, the green processing unit 25G, and the blue processing unit 25B, respectively, and then the matrix circuit 2
7 and the two color difference signals 29RY and 29BY of (RY) and (BY) are supplied to the encoder 23.

Reference numeral 37 denotes a set white balance circuit, which supplies two white balance signals 41R2 and 41B2 to the red processing section 25R and the blue processing section 25B, and controls the gains of both processing sections 25R and 25B to perform white balance. Encoder 23
Outputs a video signal 43 from a video output terminal 45 by combining a television signal with a signal supplied from the brightness processing unit 21 and the matrix circuit 27 and a synchronizing signal (not shown).

The two color difference signals 29RY and 29BY are also supplied to the setting white balance circuit 37. When the switch 39 is pressed (ON), the setting white balance circuit 37 receives the two color difference signals 29RY and 29BY, respectively. The two white balance signals 41R2 and
Both 41B2 are output controlled and white balance is set. After the switch 39 is released (OFF), the set output values of the two white balance signals 41R2 and 41B2 are held.

The power switch 47 connects and disconnects a power source (not shown) and a power circuit 49. The power supply circuit 49 generates a voltage necessary for a signal processing circuit, an image pickup device driving circuit (not shown), a synchronizing circuit and other internal circuits of the camera. The turn-on detection circuit 51 detects the turn-on of power and supplies a pulse signal 53 having a constant width to the set white balance circuit 37.

The diffuser plate 31 causes a wide range of light outside the camera to enter a color sensor (not shown) in the tracking white balance circuit 33.
With this incident light, the tracking white balance circuit 33 detects the ratio of the color components of the ambient light and generates two tracking white balance signals 35R1 and 35B1 for red and blue,
The setting white balance circuit 37 is supplied. The set white balance circuit 37 performs the normal set white balance operation after the switch 39 is pressed as described above. Also, when the power is turned on, the closing pulse 53 output from the closing detection circuit 51.
When is input, each of the two tracking white balance signals 35R1 and 35B1 for red and blue and the corresponding two white balance signals 41R2 and 41B2 for red respectively have the same voltage. To work.

The above operation is summarized as shown in FIG. First, when the power is turned on (step 61), the turn-on detection circuit 51
An input pulse 53 is generated (step 62) and both white balance signals 41R2 and 41B2 are output from the tracking white balance circuit 33. Both tracking white balance signals 35R1
And set to the same voltage as 35B1 (step 63). After that, this state is maintained until the setting switch 39 is turned on (step 64). When the setting switch 39 is turned on, the determination at step (64) is affirmative, and (RY) (BY)
Then, the operation shifts to the normal setting white balance operation so that each becomes zero (step 65). Normal white balance operation continues until switch 39 is released (step 66). When the switch 39 is turned off, the judgment at step (66) is affirmative, and both white balance signals 41R2, 41B2
Hold the output control value of (step 67) and set the step (6
Return to 4).

The setting white balance circuit 37 can be easily realized by a digital method, an analog method, or software programming of a micro computer. FIG. 3 shows a specific example using the digital method.

In FIG. 3, two smoothing circuits 71 and 73 smooth the two color difference signals 29RY and 29BY respectively introduced. The four switching switches included in the switch circuit 75 of the next stage are connected to the A side when the closing pulse 53 is not supplied. Therefore, the color difference signal 29RY is smoothed by the smoothing circuit 71 and then supplied to the inverting input terminal of one comparator 77 through the switch circuit 75. A switch circuit 75 is connected to the non-inverting input terminal of this comparator 77.
The reference voltage V _R of the DC power supply 79 is supplied through the.
Therefore, the comparator 77 receives the input color difference signal 29.
Set “0” when the smoothed signal of RY has a voltage level higher than V _R ,
When it is low, it outputs a logic signal representing "1". This output is the up-down counter 81
Is output. This signal 81 is supplied to the addition / subtraction switching input terminal U / V of the reversible counter 83. Now, assuming that the switch 39 is pushed, one input side of the AND gate 87 becomes a logic "1" through the OR gate 85. Therefore, the clock signal 89 supplied from the synchronizing circuit (not shown) is input to the clock input terminal CLK of the reversible counter 83, and the addition counting or the subtraction counting is started according to the addition / subtraction switching input. An output signal 91 of the reversible counter 83 is supplied to a digital-analog (D / A) converter 93, and a white balance signal 41R2 for performing gain control for red color is generated according to output data of the counter 83. The white balance signal 41R2 is supplied to the red processing unit 25R to control the gain on the red signal side.

With the above operation, the reversible counter 83 operates while the switch 39 is being pressed, and when the output of the smoothing circuit 71 becomes substantially equal to the reference voltage V _R , the output of the comparator 83 is inverted every clock and the setting is performed. It will be in the end state. After that, when the switch 39 is released, the reversible counter 83 stops its operation while holding the last state.

When the closing pulse 53 is "1", all the switching switches of the switch circuit 75 are connected to the B side. Thereby,
The tracking white balance signal 35R1 from the tracking white balance circuit 33 is introduced into the non-inverting input terminal of the comparator 77, and the output of the D / A converter 93 is introduced into the inverting input terminal.

Since the closing pulse 53 is applied to the other input side of the AND gate 87 via the OR gate 85, the clock signal 89 is input to the clock input terminal CLK of the reversible counter 83 to start the operation. The output of the D / A converter 93 is the tracking white balance signal 3
In the state of being almost equal to 5R1, the comparator 77 is inverted every clock as described above. After that, when the closing pulse 53 becomes "0", the operation is stopped. That is, the tracking white balance signal 35R1 output from the tracking white balance circuit 33 and the set white balance circuit 37
The white balance signal 41R2 output from the device operates so as to have the same voltage.

Although the above description has been made only for the R system, a separate comparator 95, reversible counter 97 and D / A are also provided for the B system.
A similar operation is performed by the converter 99.

FIG. 4 shows another specific example of the setting white balance circuit 37. In the figure, a reference voltage source 20 different from that shown in FIG.
That is, one and six comparators 202 to 207 are newly provided, and reversible counters 208 and 209 with presets are provided.

When the input pulse 53 is "0", the operation of setting the color difference signals to zero while the switch 39 is ON is performed like the setting white balance circuit shown in FIG.

The operation when the input pulse 53 is "1" will be described below.

The reference voltage source 201 and the comparators 202 to 207 form a kind of analog-digital (A / D) converter. That is, the input tracking white balance signals 35R1 and 35R
The preset data R _A , R _B , R _C (R system) and B _A , B of the reversible counters with presets 208, 209 are set according to the magnitude relation between the output voltage V ₁ , V ₂ and V ₃ of the reference voltage source 201 _B , B _C (B system)
Is output. Therefore, when the input pulse 53 becomes “1”, the outputs of both reversible counters 208 and 209 are the preset data R _A , R _B , R _C among the data stored therein.
And data selected by B _A , B _B , and B _C. Since the resolution of the R-system A / D conversion unit configured by the reference voltage source 201 and the three comparators 202 to 204 is low (4 steps),
Tracking white balance signal 35R1 and white balance signal
It does not exactly match 41R2, but the closest value among preset data is selected. With respect to the B system, the same operation is performed by the comparators 205 to 207 and the reversible counter 209. Needless to say, the resolution will be improved if the number of comparators is further increased.

FIG. 5 shows another embodiment of the present invention. In the figure, the first
The same reference numerals as those in the figure denote the same or corresponding circuits and the like. First
The difference from the embodiment shown in the figure is that a low luminance detection circuit 301 is added. When the brightness of the subject is sufficiently high, the smoothing circuit 30 that smoothes the output signal (Y) from the brightness processing unit 21.
The smoothed output of 2 is higher than the reference voltage Vr of the reference voltage source 303. Therefore, the output signal 305 of the comparator 304 is "0".
In this case, the set white balance circuit 37 operates normally. That is, while the switch 39 is being pressed, both color difference signals
The white balance signals 41R2 and 41B2 are controlled so that 29RY and 29BY become zero level. After releasing switch 39,
Hold this voltage.

However, there are cases where the brightness of the subject is low and the white balance cannot be set. In that case, the output of the smoothing circuit 302 becomes lower than the reference voltage Vr, and the output signal 305 of the comparator 304 becomes “1”. In response to this, the white balance signals 41R2 and 41B2 are changed to the tracking white balance signals 35R1 and 35B1 output from the tracking white balance circuit 33.
The same or close voltage value to each of the
White balance is performed by the gain control described with reference to FIG.

In the embodiment shown in FIG. 5, the voltage signal for white balance control at low brightness is set to be the same as the output voltage of the tracking white balance circuit. However, the overflow of the reversible counter and the time for pressing the setting switch are also set. The configuration may be such that it detects that a normal setting operation is not performed, such as when the setting is short.

Also, the output of the tracking auto white balance circuit 33 was used only to control the set white balance circuit 37, but a switch is provided to set the set white balance circuit 37.
The output of 37 or the output of the tracking white balance circuit 33 may be switched to be supplied as a gain control signal to the color signal processing circuit.

Further, power-on detection, low-brightness detection, overflow detection, etc. may be used in any combination.

〔The invention's effect〕

As described above in detail, according to the present invention, it is possible to provide an image pickup apparatus that can obtain a white balance with good accuracy even if an operation is forgotten or an operation is mistaken.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image pickup apparatus according to an embodiment of the present invention, FIG. 2 is a flow chart showing a white balance control operation performed in the apparatus of the present invention, and FIGS. FIG. 5 is a block diagram showing the structure of a setting white balance circuit used in the device of the present invention, and FIG. 5 is a block diagram showing the structure of an image pickup device according to another embodiment of the present invention. 10 …… Optical system 11 …… Image sensor 19R, 19G, 19B …… Color signal 29RY, 29BY …… Color difference signal 33 …… Tracking white balance circuit 35R1,35B1 …… Tracking white balance signal 37 …… Setting white balance signal 39 ...... Setting switch 41R2,41B2 …… White balance signal 51 …… Injection detection circuit 83,97,208,209 …… Reversible counter 305 …… Low brightness detection circuit

Claims (2)

[Claims] 1. A tracking white balance means for performing white balance according to a color component ratio of ambient light, a set white balance means for performing white balance according to a color component ratio in an image pickup signal, and the set white after power-on. An image pickup apparatus comprising: a control unit that controls the white balance by the output of the tracking white balance unit until the balance unit functions. 2. A tracking white balance means for performing white balance according to a color component ratio of ambient light, a set white balance means for performing white balance according to a color component ratio in an image pickup signal, and the set white balance means. When operating, the detection means detects an abnormal situation in which the white balance operation cannot be controlled, and when the abnormal situation is detected by the detection means, the control means performs white balance in accordance with the output of the tracking white balance means. And an imaging device having.