JPS61184075A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain image pickup with normal white balance by comparing an output of an automatic white balance means and an output of a color temperature detecting means of a lighting light source of an object and notifying the compared output. CONSTITUTION:An object image picked up by an optical system 1 is photoelectric- converted by an image pickup tube 2 and amplified, a luminance signal and a chrominance signal are processed by process circuits 9-12 via LPFs 4, 5, a color separation circuit 6 and LPFs 7, 8 respectively, the luminance component Y is inputted to an encoder ENA and the luminance component YL and color components R, B are inputted to a matrix circuit 13. The color difference signal being the output of the circuit 13 is inputted to the ENA14 and an automatic white balance circuit 15. The circuit 15 outputs gain control voltages Vc, Bc to control the gain of the circuits 11, 12 thereby bringing the level of the color signal to 0 level. On the other hand, the color temperature of the R, B components around the object obtained from a diffusion plate 17 is detected (20) and reference voltages RR, BR are compared with the voltages RC, BC by a comparator circuit 22. The circuit 22 outputs an alarm signal Sc when the difference of both the voltages exceed a prescribed value and displays it on a display device 23.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an imaging device.

[Prior art]

Color television cameras, particularly small home cameras, are becoming smaller and lighter and have improved image quality as electronic technology advances, and are rapidly becoming popular as a convenient means of recording video. However, although the basic performance of these cameras has improved considerably, compared to the currently popular 8mm cine cameras or still cameras, there are still areas where it is easy to make mistakes, and anyone can easily operate them. That's hard to say.

One of the most popular operations is white balance.

White balance refers to the ratio of the color components of the light source that illuminates the subject, which varies depending on the color temperature of the light source.The white balance is a method that controls the gain of the color TV's color thread by the color temperature of the light source, and adjusts the color of the white subject in the output of the camera. The signal is R:G:B=L:1
:1.

Conventionally, there are the following three methods for achieving this white balance. In other words, photograph a white subject,
The setting white balance method automatically adjusts white balance by pressing the setting button, and the tracking white balance method uses an optical system other than the imaging optical system to detect the ratio of color components in the light near the subject and performs white balance. balance method.

There are three methods that take advantage of the characteristics of both methods by combining them.

Of these, the method that combines both methods poses a particular problem in terms of operation. In the case of this method, it is necessary for the photographer to understand the advantages and disadvantages of the setting method and the tracking method before switching between them, and there is a risk of incorrect white balance adjustment if the photographer switches without fully understanding them.

For example, if the light source situation changes while using the setting method, the photographer must either reset the settings or switch to the tracking method, but sometimes the photographer does not notice this, or even if he does, he does not understand the advantages and disadvantages of both methods. Shimashima ＼ Carelessly changed the white balance to 2g! Sometimes I made a mistake in setting things up.

〔the purpose〕

The present invention attempts to solve such conventional problems, and aims to provide an imaging device that can always take images with a normal white balance.

〔Example〕

FIG. 1 is a blow diagram of an embodiment of the present invention. 1 is an imaging optical system, 2 is, for example, a frequency separation type image pickup tube, 3 is a preamplifier, 4 is a low-pass filter for the luminance signal band, °C
, 5, 7.8 are low-pass filters in the color signal band・■, f
(2) and (2), 9 are the two Y-pro upper circuits that process the luminance signal, 10 is the YL process circuit that processes the low-range luminance signal, and 6 is the color signal R and B from the imaging signal.
11 and 12 are color separation circuits that separate color signals R, respectively.
13 is a matrix circuit for synthesizing color difference signals; 14 is an encoder for synthesizing a composite video signal; 15 is an automatic white balance circuit; and 15 is an automatic white balance circuit, including a setting switch. 16
When is pressed, the outputs R-Y and B-Y of matrix 13
R process 11 and B so that
A circuit that generates the R gain control voltage Be and the B gain control voltage Be that control the gain of the process 12, 17 is a diffusion plate, 18 is an R photodetector, 19 is a B photodetector, 20 is R
a color temperature detection circuit 21 that outputs an output ratio Stc between the output voltage R of the photodetector 18 and the output voltage B of the B photodetector 19;
22 is a level conversion circuit that inputs the output ratio Stc and outputs an R reference voltage R2 and a B reference voltage BR; 22 is an R gain control voltage Be and a B gain control voltage Be; A comparison circuit 23 generates a warning signal Sc by comparing the R reference voltage RR and the B reference voltage BR, and 23 is a display device serving as a means for notifying the photographer of a warning based on the warning signal Sc.

Next, the operation will be explained. ' The object image passes through the imaging optical system 1, is photoelectrically converted by the imaging tube 2, and is amplified by the preamplifier 3. The output of the preamplifier 3 passes through a low-pass filter ■4 and is sent to the Y process circuit 9.
It is processed by and applied to the encoder 14 as a luminance signal. In addition, the output of the preamplifier 3 is separated into R and B components in the signal by a color separation circuit 6, and each component is filtered through a low-pass filter ■7 and a low-pass filter ■8.
The signal passes through an R process circuit 11 and a B process circuit 12 for processing. And this is 1 near -
It is input to the matrix circuit 13 along with the luminance signal YL processed by the YL process circuit 10 through the Hass filter 5, and the color difference signals R-YL and B-YL.
The signals are synthesized as follows and input to the encoder 14. encoder 1
4, the input luminance signal Y, color difference signals R-YL, B
-YL and a synchronization signal from a synchronization circuit (not shown), a composite video signal is synthesized and output from the video output terminal.

For example, when a white subject is photographed and the setting switch 16 is pressed, the automatic white balance circuit 13 compares the levels of the input color difference signals R-YL and B-YL with the 0 (zero) level, and calculates the results. The gains of the R process 11 and the B process 12 are set by the R gain control voltages Be and B
They are respectively varied by the gain control voltage Be, and are operated so that each of the color difference signals R-YL and B-YL is finally at the O (zero) level.

In this way, the automatic white balance operation using the known feedback control method is performed.

On the other hand, the diffusion plate 17 diffuses and condenses the light near the subject being photographed by an optical system provided separately from the imaging optical system 1, and makes the light enter the R photodetector 18 and the B photodetector 19. . Each of the detectors 18 and 19 detects a red light component and a blue light component in the peripheral area of the subject, respectively.The detected output is logarithmically compressed and subtracted by a chromaticity detection circuit 20, thereby converting it into an R component. It is output as the output ratio StC of the B component. The level conversion circuit 21 converts the level of the output ratio Stc and outputs an R reference voltage RP and a B reference voltage BR. This reference voltage R
R and BR are the R gain control voltage Be and the B gain control voltage Be when the imaging optical system 1 to the matrix 13 and the automatic white balance 15 are operating normally at the color temperature represented by the output ratio Stc. . The comparison circuit 22 is
R reference voltage RR, R gain control voltage Be and B reference voltage B
The 0 indicator 23, which outputs a warning signal Sc when the absolute value of the difference between the R and B gain control voltages Be exceeds a certain value, is a light bulb, an LED, or an electronic viewfinder placed at a location that is easily visible to the photographer. This is text, etc., which tells the photographer that the white balance is not normal! I will inform you.

FIG. 2 shows a color temperature detection circuit 20 and a level conversion circuit 21.
An example is shown below.

In the same circuit, the outputs of the R photodetector 18 and the B photodetector 19 are logarithmically compressed by Log amplifiers 101 and 102, and then subtracted by a subtracter 103.

As a result, Log(R/B) is equivalently obtained. A DC gain is set for this output ratio Stc by the gain set circuit 104, and offset levels of the R reference voltage RR and the B reference voltage BR are set by the level shift circuits 106 and 107, respectively.

According to the circuits 20 and 21, it is possible to output the R reference voltage RR and the B reference voltage BR which are approximate to the R gain control voltage Be and the B gain control voltage Be. The process will be explained with reference to FIG.

Now, it is assumed that the relationship between the gain control voltages Rc and Bc and the gain of the R process 11 and the B process 12 is shown as shown in FIG. This characteristic can be easily realized using a known balanced gain control amplifier or the like. Based on this characteristic, the color temperature of the illumination light source of the subject, and the relationship between R/G and B/G, the color temperature Tc (K) f) Reciprocal 1/Tc, R gain control voltage Re, and B gain When converted into a relationship with the control voltage Be, it becomes a first-order characteristic that loosens in the center, as shown in FIG. 2(b). On the other hand, the reciprocal 1/Tc of the color temperature Tc of the incident light of the color temperature detection circuit 20 shown in FIG. 2 and the output ratio Stc
As shown in FIG. 3(C), the relationship with Therefore, by performing negative-order transformation, that is, adjusting the slope and y-intercept of the negative-order straight line, it is possible to approximate the negative-order characteristic shown in FIG. According to the circuit 20.21 in FIG. 2, this means that the gain control voltages Rc, B
This means that it is possible to output an R reference voltage RI2 and a B reference voltage BR that are similar to c.

FIG. 4 shows an example of the comparison circuit 22.

In the figure, 201 and 202 are window comparators, 203 is an AND gate, and 204 is N.

It is a T-gate. In the window comparator 201, 205 to 208 are resistors that set the window width of the color signal R, 209 and 210 are operational amplifiers, and 211 is an AND
It is a gate. In the window comparator 202, 212 to 215 are resistors for setting one width of the color signal B, 216 and 217 are operational amplifiers, and 218 is an AND gate.

Because of this configuration, as shown in Fig. 5, the voltage of the window width set by the resistors 205 to 208 is Vw, and the width of this voltage Vw (centered on the R reference voltage Rρ) is In other words, within region I, the R gain control voltage R
When e is present, the output of the window comparator 201 is "H", indicating normal operation; however, when the R gain control voltage B
When the difference between e and R reference voltage RR becomes large and enters region (2) or m, window comparator 202 for 0 color signal B whose output becomes "L" operates in the same manner. The outputs of window comparators 201 and 202 are connected to AND gates 203 and N
Since it is output through the OT gate 204, when either window comparator 201 or 202 becomes "L", the warning signal Sc becomes "H" and a warning is output.

That is, when the balance state of either the color signal R or the color signal B is abnormal, this is notified to the photographer by the display 23.

As described above, in this embodiment, the gain control output of the automatic white balance circuit 15 and the output obtained by level-converting the output of the detection circuit 20 that detects the color temperature of the illumination light source of the subject are converted to the output of the comparison circuit 22. When the absolute value of the difference between the two is greater than or equal to a predetermined value, the display 23 is configured to warn the photographer. You can know something.

Therefore, the photographer who knows that there is an abnormality can set the white balance again before starting shooting, and can always start shooting with a normal white balance.

Although the above embodiment is an example of a single-tube type color television camera, the present invention is also applicable to other types of color television cameras, such as two-tube and three-tube color television cameras.
It can be easily applied to tube, single-plate, two-plate, or three-plate type cameras.

Further, in any camera, the imaging optical system may or may not include a color temperature conversion filter.

In the embodiment, the comparison circuit 22 compares the gain control voltage and the reference voltage separately for one color signal R and one color signal B, but even if a single reference voltage is used, the R gain control voltage Re and the B
If the gain control voltage Re has the same characteristics, it is possible to achieve the same operation, and comparing either the color signal R or the color signal B with the reference voltage will not work, except in special cases. −
A similar operation can be achieved.

The output of the color temperature detection circuit 20 and the R, H gain control voltages Rc, Bc which are the outputs of the automatic white/<lance circuit 15
The present invention can also be applied to a color television camera in which white/<lance can be performed by switching between the two. In the embodiment, when an abnormality in the white balance is detected, a notification is given, but the output may be switched to the color temperature detection circuit 20 at the same time.

Furthermore, although the level conversion circuit 21 is a primary conversion circuit, the level conversion circuit 21 is a primary conversion circuit.
If the configuration is configured to perform linear conversion or nonlinear conversion of the following order or more, the accuracy of the reference voltage can be further improved. Note that, if necessary, a part of the configuration of the embodiment can be configured by a microprogram of a microcomputer.

〔effect〕

As explained above, according to the present invention, since a warning is issued when the white balance condition is abnormal, there is no risk of photographing in an abnormal condition, and it is possible to always photograph with a normal white balance. This effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the invention, and FIG. 2 is a block diagram of an embodiment of the invention.
An example of the color temperature detection circuit and level conversion circuit in the figure, FIG. 3 is an explanatory diagram of the operation of FIG. 2, FIG. 4 is an example of the comparison circuit in FIG. 1, and FIG. 5 is an explanatory diagram of the operation of the embodiment. . In the figure, 13 is an automatic white balance circuit, 20 is a color temperature detection circuit, 21 is a level conversion circuit, 22 is a comparison circuit, 2
3 is a display device. Figure 2

Claims (1)

[Claims] an automatic white balance means for maintaining the gain of each color signal at a predetermined level; a detection means for detecting the color temperature of the illumination light source of the subject; and comparing the output of the automatic white balance means and the output of the detection means; An imaging device comprising means for notifying comparative output.