JPS60124191A - Video camera - Google Patents

Abstract

PURPOSE:To obtain a completely automatic white balance adjusting device with real time by determining the white balance of a video camera by a signal sampled at a part outputted from an image pickup part and having comparatively large quantity of a luminous signal component. CONSTITUTION:When a photographing start button is depressed, a switch 31 is turned on synchronously with the depression and a control circuit 27 starts to operate so as to enter color difference signals S21, S22 digitized by A/D converters 21, 22. If a luminous signal S2 exceeds a prescribed level, a comparator 33 detects the level and actuates the A/D converters 21, 22. The digitized color difference signals S21, S22 are successively stored in a storage circuit 30 through the control circuit 27. Every storage of a new signal in the storage circuit 30, the control circuit 27 operates a mean value of the stored digital color difference signals and supplies the mean value to comparators 23, 24 through D/A converters 26, 28. The comparators 23, 24 compare the inputted analog value with previously fixed reference values to adjust the white balance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a video camera with an automatic white balance adjustment device.

[Prior art]

Video camera white balance adjustment device [1-1 is essential. However, this adjustment method requires adjustments to be made before shooting, and there is a high possibility that important camera opportunities will be missed.

Also, even though it is called an automatic white balance method, conventional ones prepare white paper or a white filter to ensure that the light input to the camera is completely white, and then press a button. There were many failures in shooting.

An example of a circuit of a conventional automatic white balance adjustment device is shown in FIG. The signals obtained by converting the light into electrical signals by the imaging unit are a blue signal s1 from terminal 1, a brightness signal 82 from terminal 2,
A red signal s3 is output from terminal 3 and inputted. The green signal S+ and the red signal s3 are each gain-controlled by a gain control circuit 6.7 hfC, and then converted to a luminance signal s2 by an 8°9 subtraction circuit.
, to form a BY signal S4 and a hill-Y signal S5. S4 and 85 are converted into video signals and output to the outside. Picture.

Branched by S5 and smoothed by smoothing circuit 10.12 S8
S9, the comparators 13.14 output the reference voltage signal 810. from the reference voltage generator 11. So, comparison signals 812 and 813 are output, respectively. When the video camera is pointed at a white subject to adjust the white balance and the switch 20 is pressed, the signal 820 becomes the ground level and the control circuit 17 is notified to start adjusting the white balance.

16.18 consists of an up/down counter. 814 and 816 are 16°1 when adjusting white balance.
This is a signal to notify 81C. 16 and 18 are initialized at the start of white balance adjustment. 8+4 and Sly
This is the bit output signal of the A-subdown counter output from IDs 16 and 18. Srs and S+tVi are input to the DA converters 15 and 19, respectively, and converted into gain setting analog signals S+s and Egg, which are sent to the gain control circuit 6.
and enter 7. Up-down counter 16 and 181
By controlling the gains of the gain control circuits 6 and 7 by up and down by the -t clock signal, the comparison signals Su and Srs are monitored, and then Elg, 8+o, 8
The logical value of the bit output signal of the up/down counter is set and latched so that G and So match. After adjusting the white balance as with pano, take a picture using that adjusted value.

Therefore, in the conventional example, it is necessary to always carry white paper or a white filter for adjusting the white balance every time a photograph is taken. In addition, it is necessary to adjust the white balance every time the shooting conditions change.
Photographers must always be careful with white balance. Furthermore, it has been virtually impossible to make fine-grained adjustments to suit the conditions.

〔the purpose〕

The present invention solves these problems, and its purpose is to provide a fully automatic white balance adjustment device in real time.

〔overview〕

A video camera with an automatic white balance adjustment device according to the present invention is characterized in that the white balance is adjusted using a signal obtained by sampling an electric signal output from an imaging unit in a portion having a relatively large luminance signal component.

〔Example〕

The present invention will be described in detail below based on examples. First, the basic principle of the present invention will be explained. In order to photograph white more naturally, white balance adjustment converts the light when photographing a white subject into an electrical signal, and adjusts the color so that the red, blue, and green color signal components of the electrical signal are equal. It is to adjust the gain of the signal circuit. Therefore, as mentioned above, white paper and a white filter are actually used, but with this method, real-time adjustment, that is, white balance adjustment while shooting is not possible.

In order to solve this problem, the present invention utilizes the properties of the subject to realize real-time white balance adjustment. Generally speaking, the more light an object reflects, the brighter it appears. The object that reflects the most amount of light, that is, the object that reflects light of all wavelengths, is a white object. Finally, if you want to know the color of a light source (which corresponds to the color of a white object), you need to focus on objects that reflect a large amount of light, that is, bright objects. The present invention attempts to adjust white balance by sampling a portion of a video signal with a high luminance component. FIG. 2 is a diagram showing the principle of the present invention. E part 5
1 is the screen of the video camera, and the signal 851 at the bottom is a composite signal C of the luminance signal and synchronization signal of the video signal when the video camera scans a part 53 of the screen 51 (hereinafter referred to as a luminance signal). 54 indicates the luminance signal 100% level, 56 indicates the luminance signal 0 level, and 57 indicates the leading edge level of the synchronization signal.

58 is a horizontal synchronization signal. video camera ncrstc
Scanning is performed from the left along the line, and the brightness is sharp at the 520 part. This is due to the large amount of light reflected. In this case, the signal exceeds the level of 55 and has a peak value of 59. The state of the upper part 59 is detected, and at the same time, the color component signal is sampled and held. White balance is adjusted using this sample-held color component signal. The following is the principle of the present invention.

FIG. 3 shows an embodiment according to the present invention. 21 and 22 ke A
-D converter. The 31-switch switch is synchronized with the video camera's shooting switch. When switch 31 is pressed,
In response to the B-Y signal s4, the R-Y signal B, and the output signal sse of the comparator 33 becoming logic level high (hereinafter, logic level high is simply expressed as H1 logic level low is expressed as L), A -D conversion, resulting in S2□ and 822, which are input to the control circuit 27. 30#- is a memory circuit. A plurality of converted logic signals "2+" and "22" are stored in 30.

One embodiment of the present invention can be explained by dividing the control circuit 27 into two circuit systems. The first circuit system is concerned with the digitization and storage of the color difference signals S4 and S. The second circuit system is related to calculating the average value of the dental signal and correcting the white balance.

First, the first circuit system will be explained. When the photographing start button is pressed, the switch 31 synchronized with the button is turned on, and the control circuit 27 starts operating to increase the color difference signals s21 and '22 converted by the A-D converters 21 and 22. FIG. 4 is an explanatory diagram regarding the operation timing of the AD converters 21 and 22. Is 32 in FIG. 3 the reference for generating the voltage level signal 835 at 55 in FIG. 4? This is a pressure generation circuit.

When the luminance signal of S2 exceeds the voltage level of 55, the comparator 33 detects it and sets the output "se" to H.
61 and 65 in the figure are the parts. When S3a becomes H, the color difference signals S, , S, corresponding to the color signal J, 83 become A-D.
It is digitized by converters 21 and 22.

Parts to be digitized 63.64.67゜6
It is 8. The digitized color difference signals S2□ and "22 are controlled by the control circuit 27 and become 830, and the storage circuit 3
Stored as 0. The control circuit 27 controls the storage circuit 30 and sequentially stores the digitized color difference signals in the storage circuit 30. When the storage circuit 30 overflows, the oldest signal is erased and the next new signal is stored. Next, the second circuit system will be explained. Every time a new signal is stored in the storage circuit 30, the control circuit 27 calculates the average value of each of the stored and digitized color difference signals in the storage circuit 301.

The average values become "23." and "24," respectively, and are sent to DA converters 26 and 28, where they are converted into analog signals. 2
5 and 291d are reference voltage generation circuits. The signal s3 outputted from 25 and 29 is a reference signal for setting the white balance, and is set to an optimum value in advance. Comparators 23 and 24 compare S25 and S26, S27 and "28, respectively, and output comparison signals S3. and 8.
Outputs 34. Control circuit 271-1.5311 and 83
While monitoring s2.4 to the D-A converters 26 and 28 so that the inputs of the respective comparators match #1. Sends 1 and 824 digital signals.

Next, the control circuit 27 calculates the difference between the average value of the digital color difference signals initially sent to the D-A converters 26 and 28 and the digital signal sent so as to match the reference voltage and voltage signals 26 and 828.
From S2. and S32, respectively, to the A-D converters 15 and 19. Output signals of A-D converters 15 and 19 "1"
8 and S8. is input as a white balance adjustment signal to gain control circuits 6 and 7, and color difference signals s1 and 8. control the gain and adjust the white balance.

〔effect〕

As described above, according to the present invention, the white balance can be adjusted in real time, so even if the shooting situation changes, corrections can be made to the white balance one after another.

Furthermore, since there is no possibility of forgetting to make adjustments, there are fewer mistakes in shooting. Since the adjustment is made using the temporal average value of the photographed (l!), there is no need for a white filter or sensor for white balance adjustment, and a simple video camera configuration is possible. Since the white balance according to the present invention uses the peak of the luminance signal, it is highly accurate.(6) The diagonal circuit for realizing the present invention can be easily constructed using a semiconductor circuit, and Furthermore, the present invention is not limited to the above-described digitalization embodiment, but can also average video signals in an analog manner.

Application examples of the present invention include not only video cameras but also a wide range of applications such as video tape recorders, television playback devices, etc. In the case of video tape recorders, television playback devices that automatically adjust the white balance of recorded signals In this case, the main task is to reproduce the reproduced image in an optimal white balance state.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional white balance adjustment device. Figure 2 FA'l, el) is a diagram showing the principle of the present invention,
Figure pX3 is a circuit diagram of an embodiment according to the present invention. FIG. 4 is an explanatory diagram regarding the operation timing of the A-D converter. 4... Output terminal for B-Y signal 5... Output terminal for R-Y signal S31... Signal to inform control circuit 27 of starting white balance adjustment E Exit door People Suwa Seikosha Co., Ltd.

Claims (1)

[Claims] In a video camera that includes at least an imaging section that converts light into an electrical signal, an optical section that guides the light to the imaging section, and a circuit section that processes the electrical signal, the white balance of the video camera is A video camera with an automatic white balance adjustment device, characterized in that the electric signal output from the section is determined by a signal sampled in a portion having a relatively large luminance signal component.