JPH04248794A - White balance controller for video camera - Google Patents

Abstract

PURPOSE:To prevent malfunction of white balance in the video processing system. CONSTITUTION:When the on-operation of a power switch 28 of a video camera is detected and a change width of a luminous quantity detected by a Hall element 25 exceeds a specified value, a zoom motor 26 is driven to once shift a zoom lens toward the wide angle position, after the white balance is adjusted with the zoom lens set to the wide angle position, the zoom motor 26 is again driven to shift the zoom lens to a prescribed zoom position.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a video camera.
More specifically, the present invention relates to a white balance control device that can prevent white balance malfunctions in video signal processing systems.

0002

2. Description of the Related Art FIG. 2 shows the electrical configuration of a video camera that performs white balance control using a conventional video signal processing method.

In the figure, illumination light of an object (not shown) is transmitted through a lens system 51 which is a component of a video signal processing system 50.
The output of the image sensor 52 is passed through a preamplifier 53 and guided to an image sensor 52 made of a CCD or the like.
It is led to a luminance signal processing circuit 54 that generates a luminance signal, and a color signal processing circuit 55 that generates an R signal, a G signal, and a B signal.

[0004] Each output of the color signal processing circuit 55 that sends out the generated R signal, G signal, and B signal is sent to an R gain circuit 56, a G amplifier circuit 57, and a B gain circuit 58 provided correspondingly. and each R gain circuit 5
6. The outputs of the G amplifier circuit 57 and the B gain circuit 58 are:
It is led to a matrix circuit 59. Then, the R-Y color difference signal and the B-
The Y color difference signal is guided to a chroma modulation circuit 62.

The chroma modulation circuit 62 has a frequency fsc1.
, fsc2 are guided, and the output of the chroma modulation circuit 62 is guided to one input of the mix circuit 63. Further, the output of the luminance signal processing circuit 54 is led to the other input of the mix circuit 63, and the output of the mix circuit 63 is sent as a composite video signal to a subsequent signal processing system (not shown).

Further, the R-Y color difference signal and the B-Y color difference signal generated in the matrix circuit 59 are sent to respective smoothing circuits 76 and 77, which are components of the white balance control system 70, which are provided correspondingly. It is also guided by
Each output of each smoothing circuit 76, 77 is led to each negative terminal of a correspondingly provided comparison circuit 74, 75.

[0007] Further, a reference voltage Vref is applied to the positive terminal of each comparison circuit 74, 75, and the output of each comparison circuit 74, 75 is connected to each up/down terminal provided correspondingly.
It is led to down counters 71 and 72.

Here, the level of the reference voltage Vref is:
It is set to the same zero level as the level of the blanking period of the color difference signal.

[0009] Also, each up/down counter 71, 7
2 is led to the output of a hold switch 73 that holds the white balance control at a certain level, and the output of each up/down counter 71, 72 is sent to the corresponding R gain circuit 56 as a gain control signal.
, B gain circuit 58.

In the above configuration, the illumination light of the object that has passed through the lens system 51 is converted from optical information to an electrical signal in the image sensor 52, and then amplified in the preamplifier 53 to a level necessary for various signal processing. The signal is input to a luminance signal processing circuit 54 and a color signal processing circuit 55.

The luminance signal processing circuit 54 generates a luminance signal from the input signal, and sends the generated luminance signal to the mix circuit 63.
Enter.

The color signal processing circuit 55 separates the R signal, G signal, and B signal from the input signal, and the separated R signal, G signal, and B signal are processed by the R signal provided correspondingly. The signal is input to the matrix circuit 59 via the gain circuit 56, the G amplifier circuit 57, and the B gain circuit 58.

In the matrix circuit 59, the G amplifier circuit 5
Calculation is performed using the level of the G signal input from 7 as a reference to generate an R-Y color difference signal and a B-Y color difference signal, and input them to the chroma modulation circuit 62.

The chroma modulation circuit 62 performs balanced modulation of each color difference signal using carrier waves of frequencies fsc1 and fsc2 to generate a chroma signal, which is input to a mix circuit 63. Then, in this mix circuit 63, the luminance signal and the chroma signal are mixed, resulting in a composite video signal.
It is then sent to the signal processing system.

On the other hand, the levels of the R-Y color difference signal and the B-Y color difference signal generated in the matrix circuit 59 are averaged in respective smoothing circuits 76 and 77 provided correspondingly. It is input to the negative terminal of each comparison circuit 74, 75.

The positive terminal of each comparison circuit 74, 75 has a
Since the reference voltage Vref is given, each comparison circuit 74, 75 calculates the level difference between the reference voltage Vref and the R-Y color difference signal and B-Y color difference signal input to each negative terminal, and calculates the level difference. A signal indicating the difference is input to each up/down counter 71, 72.

The up/down counter 71 operates based on the signal input from the comparator circuit 74 and eliminates the level difference indicated by the signal (that is, the comparator circuit 74
The gain of the R gain circuit 56 is controlled so that the average level of the R-Y color difference signal input to the negative terminal of the R gain circuit 56 becomes equal to the level of the reference voltage Vref. Furthermore, in the up/down counter 72, a comparison circuit 75
Based on the signal input from ) Performs gain control of the B gain circuit 58.

The hold switch 73 is a switch for holding the above-mentioned white balance control at a certain level. By pressing this hold switch 73, the operation of each up/down counter 71, 72 is stopped. , the current level is maintained.

[0019]

[Problem to be Solved by the Invention] As mentioned above, with white balance control using the video signal processing method, there is no problem when the subject is black and white, but when the subject is chromatic, the average level of the color difference signal is Since the level is not necessarily zero (the level during the retrace period of the color difference signal or the level of the reference voltage Vref), there is a problem in that an error occurs accordingly. In particular, in the case of a single color, the color becomes lighter and fades.

By the way, even when photographing a chromatic object, when photographing with a zoom lens at the wide angle side, the average level of the color difference signal almost always matches the zero level. The present invention was made in view of the above circumstances, and its purpose is to automatically shift the zoom lens to the wide side and adjust the white balance when starting shooting or when the amount of light on the subject changes significantly. An object of the present invention is to provide a white balance control device for a video camera.

[0021]

[Means for Solving the Problems] In order to solve the above-mentioned problems, a white balance control device for a video camera according to the present invention controls the gains of the R signal and B signal created in the video signal processing system. When a device that adjusts white balance detects that the video camera is powered on, it drives the zoom motor to temporarily shift the zoom lens to the wide-angle side, and after adjusting the white balance on the wide-angle side of the zoom lens. , a control means for driving the zoom motor again to shift the zoom lens to a predetermined zoom position.

Further, the white balance control device for a video camera according to the present invention adjusts the white balance by controlling the gains of the R signal and B signal created in the video signal processing system. A detection means for detecting a change in the amount of light, and when the range of change in the amount of light detected by this detection means exceeds a specified value, drives a zoom motor to temporarily shift the zoom lens to the wide-angle side, and also shifts the zoom lens to the wide-angle side. After the white balance is adjusted in step 1, the zoom motor is driven again to shift the zoom lens to a predetermined zoom position.

[0023]

[Operation] When the control means detects that the power switch is turned on, it drives the zoom motor to temporarily shift the zoom lens to the wide-angle side. After adjusting the white balance on the wide-angle side of this zoom lens,
The control means drives the zoom motor again to shift the zoom lens to a predetermined zoom position.

Further, the control means drives the zoom motor to temporarily shift the zoom lens to the wide-angle side when the range of change in the amount of light from the object detected by the detection means exceeds a specified value. After adjusting the white balance on the wide-angle side of the zoom lens, the control means drives the zoom motor again to shift the zoom lens to a predetermined zoom position.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the electrical configuration of a video camera equipped with a white balance control device of the present invention.

In the figure, 1 is a lens system including a zoom lens, 2 is an image sensor, 3 is a preamplifier, 4 is a luminance signal processing circuit, 5 is a color signal processing circuit, 6 is an R gain circuit, and 7
is a G amplifier circuit, 8 is a B gain circuit, 9 is a matrix circuit, 12 is a chroma modulation circuit, 13 is a mix circuit, 20
, 21 are up/down counters, 18 and 19 are comparison circuits, and 15 and 16 are smoothing circuits, and since these structures are similar to the conventional circuit structure described above, detailed explanation will be omitted here.

Further, 23 is an iris motor drive circuit;
4 is an iris motor, 25 is a Hall element built into the iris motor 24, 26 is a zoom motor that drives the zoom lens, and 27 is a zoom motor drive circuit, and these configurations are also installed in conventional video cameras. It is similar to

In the present invention, in the above configuration, when an on operation of the power switch 28 of the video camera is detected and when a change in the amount of light detected by the Hall element 25 is large, the zoom motor drive circuit 27 and each up/down counter 20 and 21, and also outputs a control signal to the zoom motor drive circuit 27 when an adjustment completion signal from each up/down counter 20 and 21 is detected.

That is, the control circuit 30 detects the ON operation of the power switch 28 of the video camera, and thereby
The zoom motor 26 is controlled by controlling the zoom motor drive circuit 27.
The up/down counters 20,
A control signal indicating the start of operation is output to 21, and each up/down
The down counters 20 and 21 are operated. Then, upon receiving a signal from each up/down counter 20, 21 indicating the completion of white balance adjustment, the zoom motor drive circuit 27 is controlled again, and the zoom motor 26 is driven to shift the zoom lens to a predetermined zoom position. control.

Furthermore, when the change in the amount of light detected by the Hall element 25 exceeds an internally set standard value, the control circuit 30 controls the zoom motor drive circuit 27 to drive the zoom motor 26 and close the zoom lens. At the same time, a control signal indicating the start of operation is output to each up/down counter 20, 21 to operate each up/down counter 20, 21. Then, each close-up /
Upon receiving the signals from the down counters 20 and 21, the zoom motor drive circuit 27 is again controlled to drive the zoom motor 26 and shift the zoom lens to a predetermined zoom position.

Note that the control circuit 30 that performs such operation control is configured by software that operates on a microcomputer. Next, the operation of the video camera equipped with the white balance control device configured as described above will be explained.

When the operator of the video camera turns on the power switch 28 to take a picture, the control circuit 30 detects the on operation of the power switch 28 and controls the zoom motor drive circuit 27 to turn on the zoom motor. 26 to perform control to temporarily shift the zoom lens to the wide side. Further, the control circuit 30 simultaneously outputs a control signal indicating the start of operation to each up/down counter 20, 21, thereby causing each up/down counter 20, 21 to operate.

As a result, the white balance control system operates and adjusts the white balance so that the output of each smoothing circuit 15, 16 (ie, the average level of each color difference signal) becomes zero level.

That is, since the white balance is adjusted by shifting the zoom lens to the wide side, the average value level of the color difference signal will match the zero level in most cases.

When the white balance adjustment is completed, an adjustment completion signal is sent from each up/down counter 20, 21 to the control circuit 30, and upon receiving this signal, the control circuit 30 starts the zoom motor drive circuit 27 again. control,
Control is performed to drive the zoom motor 26 to shift the zoom lens to a predetermined zoom position. After this, it is possible to hold the white balance, but in order to be able to follow small changes, the control range can be adjusted from 1/3 to 1/3.
Try to narrow it down to about 5 and operate it.

[0037] Furthermore, when changing from indoor photography to outdoor photography, the white balance will shift if the change in light amount is large. Therefore, in this case, the change in light amount is detected by the Hall element 25 and the detected value is sent to the control circuit 30.

The control circuit 30 controls the zoom motor drive circuit 27 when the change in the amount of light detected by the Hall element 25 exceeds an internally set standard value (that is, when the amount of light changes significantly). The zoom motor 26 is driven to perform control to temporarily shift the zoom lens to the wide side. Further, the control circuit 30 simultaneously outputs a control signal indicating the start of operation to each up/down counter 20, 21, thereby causing each up/down counter 20, 21 to operate.

As a result, the white balance control system operates, and the white balance is adjusted so that the output of each smoothing circuit 15, 16 (that is, the average level of each color difference signal) becomes zero level. When the white balance adjustment is completed, an adjustment completion signal is sent from each up/down counter 20, 21 to the control circuit 30, so the control circuit 30 that receives this signal controls the zoom motor drive circuit 27 again. Control is performed to drive the zoom motor 26 to shift the zoom lens to a predetermined zoom position. Thereafter, the white balance control range is narrowed to about 1/3 to 1/5 for operation.

[0040]

Effects of the Invention The white balance control device for a video camera according to the present invention drives the zoom motor to control the zoom lens when it detects that the power of the video camera is turned on or when the range of change in the amount of light of the subject exceeds a specified value. Since the camera is configured so that the white balance is adjusted by once shifting the camera to the wide-angle side, it is possible to prevent the occurrence of white balance errors that tend to occur in video cameras using the video signal processing method.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical configuration of a video camera equipped with a white balance device of the present invention.

FIG. 2 is a block diagram showing the electrical configuration of a video camera equipped with a conventional white balance device.

[Explanation of symbols]

1 Lens system 4 Luminance signal processing circuit 5 Color signal processing circuit 6 R gain circuit 7 G amplifier circuit 8 B gain circuit 9 Matrix circuit 15, 16 Smoothing circuit 18, 19 Comparison circuit 20, 21 Up/down counter 25 Hall element 26 Zoom Motor 28 Power switch 30 Control circuit

Claims (2)

[Claims] [Claim 1] R created in a video signal processing system
In a white balance control device that adjusts white balance by controlling the gain of the signal and the B signal, when power-on of the video camera is detected, the zoom motor is driven to temporarily shift the zoom lens to the wide-angle side. , a white video camera comprising a control means for controlling the zoom lens to shift the zoom lens to a predetermined zoom position by driving the zoom motor again after adjusting the white balance on the wide-angle side of the zoom lens. Balance control device. [Claim 2] R created in a video signal processing system
A white balance control device that adjusts white balance by controlling the gain of a signal and a B signal includes a detection means for detecting a change in the amount of light of a subject, and a width of change in the amount of light detected by this detection means that is within a specified value. When it exceeds the limit, the zoom motor is driven to temporarily shift the zoom lens to the wide-angle side, and the white balance is adjusted on the wide-angle side of the zoom lens, and then the zoom motor is driven again to shift the zoom lens to the specified zoom position. 1. A white balance control device for a video camera, comprising: a control means for controlling a white balance to be shifted to a white balance of a video camera.