JPH06101846B2 - Imaging device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an imaging device.

[Prior art]

BACKGROUND ART Color television cameras, particularly household small-sized cameras, have been rapidly becoming widespread as a handy video recording means with the progress of smaller and lighter weight and improved image quality with the progress of electronic technology. However, although these cameras have improved considerably in their basic performance, there are still some parts that are erroneous to operate compared to the currently popular 8 mm cine camera or still camera, and anyone can operate them easily. Is hard to say.

One of the mistaken operations is white balance.

White balance means that the ratio of the color components of the light source that illuminates the subject differs depending on the color temperature of the light source.Therefore, the gain of the color thread of the color TV is controlled by the color temperature of the light source, and the color of the white subject in the camera output is controlled. Adjust the signal to be R: G: B = 1: 1: 1.

Conventionally, there are the following three methods for achieving the white balance. That is, a white subject is photographed,
A tracking type white balance that automatically adjusts the white balance by pressing the setting button, and an optical system other than the imaging optical system detects the ratio of the color components in the light near the subject to achieve white balance. There are three methods, a balance method and a method that makes full use of these features by combining both methods.

Of these, the method that combines both methods is particularly problematic in 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 and switch between them, and if the switching is not fully understood, there is a risk that the white balance adjustment may be erroneous.

For example, when the light source conditions change while using the setting method, you have to reset or switch to the tracking method, but the photographer does not notice it or understands the advantages and disadvantages of both methods. If you don't do so, you may accidentally switch the white balance by mistake.

〔Purpose〕

The present invention is intended to solve such a conventional problem, and an object of the present invention is to provide an imaging device capable of always taking a picture with a normal white balance.

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention. 1 is an image pickup optical system, 2 is a frequency separation type image pickup tube, 3 is a preamplifier, 4 is a luminance signal band low-pass filter, 5,
7 and 8 are low-pass filters in the color signal band, and 9
Is a Y process circuit for processing the luminance signal, 10
Is a Y _L process circuit for processing the low band luminance signal, 6 is a color separation circuit for separating the color signals R and B from the image pickup signal, and 11 and 12 are R for processing the color signal R and the color signal B, respectively. A process circuit and a B process circuit, 13 is a matrix circuit for synthesizing color difference signals, 14 is an encoder for synthesizing composite video signals, 15 is an automatic white balance circuit, and when the setting switch 16 is pressed, the matrix 13
The circuit for generating the R gain control voltage Rc and the B gain control voltage Bc for controlling the gains of the R process 11 and the B process 12 so that the outputs R-Y and B-Y of 0 become zero level, 17 is a spreader. Plate, 18 R photo detector, 19 B photo detector,
20 color temperature detection circuit for outputting an output ratio Stc of the output voltage R of the R light detector 18, and the output voltage B of the B light detectors 19, 21 enter the output ratio Stc R reference voltage R _R, B reference voltage _BR
A level conversion circuit 22 for outputting the R gain control voltage Rc, the B gain control voltage Bc, the R reference voltage _RR, and the B reference voltage _BR
Comparing circuit that generates a warning signal Sc by comparing
Reference numeral 23 is a display as means for notifying the imager of the warning by the warning signal Sc.

Next, the operation will be described.

The subject image passes through the image pickup optical system 1, is photoelectrically converted by the image pickup tube 2, and is amplified by the preamplifier 3. The output of the preamplifier 3 passes through the low pass filter 4 and the Y process circuit 9
Is added to the encoder 14 as a luminance signal. Further, in the output of the preamplifier 3, the R component and the B component in the signal are separated by the color separation circuit 6, the respective components pass through the low pass filter 7 and the low pass filter 8, and the R process circuit 11 and the B process 12 Processed by And this is the low-pass filter 5
It is input to the matrix circuit 13 together with the luminance signal Y _L processed by the Y _L process circuit 10 and is combined there as color difference signals R-Y _L and B-Y _L to enter the encoder 14. In the encoder 14, the input luminance signal Y, color difference signals _{R-Y L, B-Y} L and the composite video signal by the synchronizing signal from the synchronizing circuit (not shown) are synthesized and outputted 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 color difference signals R-Y _L and B-Y _L that are input with the 0 (zero) level, As a result, the gains of the R process 11 and the B process 12 are changed by the R gain control voltage Rc and the B gain control voltage Bc, respectively, and finally each color difference signal RY
It operates so that _{L 1} and B−Y _L each become 0 (zero) level.

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

On the other hand, the diffusing plate 17 diffuses and collects light near the subject being photographed by an optical system provided separately from the imaging optical system 1,
The light enters the R photodetector 18 and the B photodetector 19. Each detector 18
And 19, the red light component and the blue light component in the peripheral part of the subject are detected. The detected output is the color temperature detection circuit 20.
The logarithmic compression and the subtraction are performed in step S3 to output the output ratio Stc of the R component and the B component. Level converting circuit 21, converts the level of the output ratio Stc, outputs the R reference voltage R _R and B reference voltage B _R. The reference voltages R _R and B _R are R gain control voltages Rc and B gain 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 control voltage is Bc. The comparison circuit 22 uses the R reference voltage _RR and the R gain control voltage.
The absolute value of the difference Rc and B reference voltage B _R and B gain control voltage Bc outputs a warning signal Sc when exceeds a predetermined value. Display 23
Is placed in a position that is easy for the photographer to see, such as a light bulb or LE
D, or letters on the electronic viewfinder, etc., to alert the photographer that the white balance state is not normal.

FIG. 2 shows an example of the color temperature detection circuit 20 and the level conversion circuit 21.

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 a subtractor 103
Is subtracted. As a result, Log (R / B) is equivalently obtained. The output ratio Stc, set the DC gain by the gain set circuit 104, the offset level of the R reference voltage R _R and B reference voltage B _R each of which is set by the level shift circuit 106 and 107.

According to the circuits 20 and 21, the R gain control voltage Rc and the B gain control voltage Bc are approximated to the R reference voltage R _R and the B reference voltage B, respectively.
_R can be output. The process will be described with reference to FIG.

Now, the gain control voltage Rc of R process 11 and B process 12
Assume that the relationship between Bc and Bc and the gain is shown in FIG. This characteristic can be easily realized by a known balanced amplification type gain control amplifier or the like. This characteristic is determined by the relationship between this and the color temperature of the illumination light source of the subject and R / G and B / G.
When converted to the relationship between the reciprocal 1 / Tc of [K] and the R gain control voltage Rc and the B gain control voltage Bc, almost a primary characteristic is obtained in the central portion as shown in FIG. On the other hand, the reciprocal 1 / Tc of the color temperature Tc of the incident light and the output ratio St of the color temperature detection circuit 20 shown in FIG.
The relationship with c is a primary characteristic as shown in FIG.
Therefore, this can be approximated to the primary characteristic by linear transformation, that is, by adjusting the inclination of the linear line and the y-intercept. This means according to the circuit 20, 21 of FIG. 2 R, gain control voltage Rc of B, to be able to output the R reference voltage approximate to the Bc R _R and B reference voltage B _R.

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

In the figure, 201 and 202 are window comparators, and 203 is
AND gate and 204 are NOT gates. In the window comparator 201, 205 to 208 are resistors that set the window width of the color temperature R, 209 and 210 are operational amplifiers, and 211 is an AND gate. In the window comparator 202, 212
~ 215 is a resistor for setting the window width of the color signal B, 216,
217 is an operational amplifier, and 218 is an AND gate.

With such a configuration, as shown in FIG. 5, the voltage of the window width set by the resistors 205 to 208 is now Vw.
And then, within the width of the voltage Vw (around the R reference voltage R _R), that is, when there is R gain control voltage Rc is in the region I, the output of the window comparator 201 a normal operation at "H" Show. However, R gain control voltage Rc and R reference voltage R
_When the difference in _R becomes large and enters the region II or III, the output becomes "L". The window comparator 202 for the color signal B operates similarly. Since the outputs of the window comparators 201 and 202 are output through the AND gate 203 and the NOT gate 204, if either of the window comparators 201 or 202 becomes "L", the warning signal Sc becomes "H" and a warning is output. It That is, when the white balance state of either the color signal R or the color signal B is abnormal, this is notified to the photographer by the display device 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 compared with each other. When the absolute value of the difference between the two is greater than or equal to a predetermined value, the display unit 23 is configured to warn the imager, so that the imager who receives the warning determines that the white balance state is abnormal. You can know that there is.

Therefore, the image-capturing person who knows that the image is abnormal can set the white balance again before starting the image-taking, and can always start the image-taking with the normal white balance.

The above embodiment is an example of a single-tube type color television camera, but the present invention is not limited to this, and other embodiments, for example, a two-tube, three-tube type,
It can be easily applied to a tube or a single plate, two plate, or three plate camera.

Further, in any of the cameras, the image pickup optical system may or may not include the color temperature conversion filter.
In the embodiment, the comparison circuit 22 compares the gain control voltage and the reference voltage separately for the color signal R and the color signal B.
Even if a single reference voltage is used, if the R gain control voltage Rc and the B gain control voltage Bc have almost the same characteristics, the same operation can be realized, and one of the color signal R and the color signal B can be realized. Even if is compared with the reference voltage, almost the same operation can be realized except for a special case.

Output of color temperature detection circuit 20 and automatic white balance circuit
The present invention can also be applied to a color television camera of a system in which the gain control voltages Rc and Bc of R and B which are outputs of 15 can be switched to achieve white balance between the two. In the embodiment, when the abnormality of the white balance is detected, it is notified, but the output may be switched to the color temperature detection circuit 20 at the same time.

Further, although the level conversion circuit 21 is a primary conversion circuit, the accuracy of the reference voltage can be further improved if it is configured to perform a linear conversion or a non-linear conversion of secondary or higher order.
In addition, if necessary, a part of the configuration of the embodiment may be configured by a micro program of a microcomputer.

〔effect〕

As described above, according to the present invention, since the warning is issued when the state of white balance is abnormal, there is no possibility of photographing in an abnormal state, and it is possible to always photograph with normal white balance. The effect is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a first diagram.
FIG. 3 is an operation explanatory diagram of FIG. 2, FIG. 4 is an example of the comparison circuit in FIG. 1, and FIG. 5 is an operation explanatory diagram 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, and 23 is a display.

Claims (1)

[Claims] 1. An image pickup unit, a variable gain control amplifying unit for changing the gains of a plurality of color signals formed by the image pickup unit, and the variable gain control based on the signal formed by the image pickup unit. A gain control signal forming means (15) for forming a gain control signal for adjusting the white balance by adjusting the gain of the amplifying means, and a color temperature for detecting the color temperature of a subject provided separately from the image pickup means. An image pickup device comprising: a detection means (20, 21); and a display means for comparing the gain control signal with the output of the color temperature detection means and displaying the comparison result.