JPH0432393A - Color image pickup device - Google Patents

Abstract

PURPOSE:To attain excellent color display at application of power by arranging a white color board in front of a lens means in response to application of power and removing the white color board from the front face of the lens means in response to the end of white balance adjustment at application of power by a white balance adjustment means. CONSTITUTION:A white balance microcomputer 14 outputs a signal controlling a slide cap drive circuit 17 to drive a motor 4 in opposite direction to that at application of power as the result of white balance adjustment at application of power. Thus, white boards 1a, 1b are slided horizontally respectively to release the interruption between a lens system 19 and an external light. After the white balance microcomputer 14 opens the white slide cap 1, an object image fetched by the lens 19 is displayed on a monitor screen and recorded on a magnetic tape as a video signal. Thus, no decoloring is caused in the pickup picture at application of power to obtain an excellent picture with high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color imaging device, and more particularly to a color imaging device with an improved white balance function.

[Prior Art] A color imaging device such as a color video camera has a white balance function for displaying a subject on a screen in the same color as seen by the human eye.

Human eyes perceive white objects as white regardless of changes in the color temperature of the illumination light of the object to be viewed. However, the color of an object captured by a color imaging device becomes more bluish as the color temperature of the illumination light is higher, and becomes more reddish as the color temperature of the illumination light is lower. In other words, the color perceived by the color imaging device and the color perceived by the human eye differ depending on the color temperature of the illumination light.

Therefore, color imaging devices are equipped with a white balance function that automatically adds correction to color information obtained by imaging a subject according to the color temperature of the illumination light of the subject.

FIG. 5 is a schematic block diagram of a conventional color video camera.

Referring to FIG. 5, when the camera is in the camera position, reflected light from the subject passes through the lens system 19 and forms an optical image of the subject on the light receiving surface of the image sensor 20. The image sensor 20 converts the optical image formed on the light-receiving surface into an electrical signal and sends it to a luminance signal processing circuit 21.
and is applied to the chroma signal processing circuit 22.

The brightness signal processing circuit 21 extracts only the signal component indicating the brightness of the subject from the electrical signal applied from the image sensor 20, and inputs this extracted signal as the brightness signal Y to the adder 28.

The chroma signal processing circuit 22 separates a signal component indicating the color of the subject from the electrical signal given from the image sensor 20, and creates primary color signals R and B corresponding to red and blue, respectively, from the separated signal components. do. At the same time, the chroma signal processing circuit 22 creates a luminance signal (narrowband luminance signal) YL having a narrower band than the aforementioned luminance signal Y from the electrical signal provided from the image sensor 20. This narrowband luminance signal Y8. is a signal created to obtain a luminance signal having a frequency band matching the frequency band of the primary color signals R and B, and unlike a normal luminance signal Y, high frequency components are removed. Primary color signals R and B are provided to an R gain control circuit 23 and a B gain control circuit 24, respectively.

The narrowband luminance signal Y, is applied to the inverting input terminals of subtracters 25 and 26.

The R gain control circuit 23 adjusts the gain of the primary color signal R provided from the chroma signal processing circuit 22 in accordance with the control signal G provided from the white balance adjustment circuit 33.

This gain-adjusted primary color signal R is applied to the non-inverting input terminal of the subtracter 25.

Similarly, the B gain control circuit 24 controls the chroma signal processing circuit 2.
The gain of the primary color signal B given from 2 is adjusted in accordance with another control signal GB given from the white balance adjustment circuit. This gain-adjusted primary color signal B is applied to the non-inverting input terminal of the subtracter 26.

The subtracter 25 subtracts the narrowband luminance signal YL applied to the inverting input terminal from the gain-adjusted primary color signal R applied to the non-inverting input terminal to derive a color difference signal RY. Similarly, the subtracter 26 subtracts the narrowband luminance signal YL applied to the inverting input terminal from the gain-adjusted primary color signal B applied to the non-inverting input terminal to derive the color difference signal B-Y. These color difference signals R-Y and B-Y are both sent to the modulator 27.
and the white balance adjustment circuit 33.

The modulator 27 receives the applied color difference signals R, -Y and B-
The chroma signal C is superimposed on subcarriers whose phases differ by 90 degrees from each other, and the subcarriers on which the color difference signals are superimposed are synthesized to generate a chroma signal C.
Derive. In this way, the modulator 27 creates a chroma signal C by balanced modulating the applied color difference signals R-Y and B-Y. The created chroma signal C is given to the adder 28.

The adder 28 combines the luminance signal Y supplied from the luminance signal processing circuit 21 and the chroma signal C supplied from the modulator 27. At the same time, the adder 28 is connected to the synchronization signal generator 2.
A predetermined synchronization signal is given from 9. Synchronous signal generator 2
9 is a vertical synchronization signal.

It outputs synchronization signals required for NTSC composite color video signals, such as horizontal synchronization signals and color burst signals. The adder 28 adds these synchronization signals to a signal obtained by combining the luminance signal Y and the chroma signal C. The signal to which the synchronization signal is added in this way is the composite color video signal output from this video camera.

The white balance adjustment circuit 33 includes an averaging circuit 30, a white balance microcomputer (hereinafter abbreviated as microcomputer) 31. and a D/A converter 32. The color difference signals R-Y and B-Y input from the subtracters 25 and 26 to the white balance adjustment circuit 33 are sent to the averaging circuit 3.
It is input to 0. The averaging circuit 30 averages the applied color difference signals RY and B-Y, for example, for each screen, and outputs the averaged signals. As a result, the averaging circuit 30 outputs voltages corresponding to the respective average levels of the color difference signals RY and BY. The white balance microcomputer 31 creates control signals to be given to each of the R gain control circuit 23 and the B gain control circuit 24 based on the voltage output from the averaging circuit 30, and outputs them as digital signals.

The D/A converter 32 converts a digital signal corresponding to a control signal to be given to the R gain control circuit 23 and a digital signal corresponding to a control signal to be given to the B gain control circuit 24 from the white balance microcomputer 31 into analog form. Convert to voltage. The converted analog voltages are each given to a corresponding gain control circuit (R gain control circuit 23 or B gain control circuit 24) as control signals GR and Gn.

Both the R gain control circuit 23 and the B gain control circuit 24 are variable gain amplifiers that operate to change the gain of the input signal according to an external control voltage. Therefore, by controlling the level of the analog voltage output from the D/A converter 32, the gains of the primary color signals R and B can be changed arbitrarily. Accordingly, the average level of the color difference signals R-Y and B-Y output from the subtracters 25 and 26, respectively, also changes arbitrarily.

Therefore, the white balance microcomputer 31 determines that the gain of the primary color signal R makes the average level of the output of the subtractor 25 0 based on the average level of the color difference signal R-Y detected by the averaging circuit 30. The value that can be obtained is as follows.
The magnitude of the control voltage for the R gain control circuit 23 is derived. At the same time, the white balance microcomputer 31 allows the gain of the primary color signal B to set the average level of the output of the subtracter 26 to 0 based on the average level of the color difference signal B-Y detected by the averaging circuit 30. value,
The magnitude of the control voltage for the B gain control circuit 24 is derived. (7) The white balance microcomputer 31 outputs a digital signal indicating the magnitude of these derived control voltages.Thereby, the R gain control circuit 23 and the B gain control circuit 24 control the color difference signal RY. The gains of the primary color signals R and B are adjusted so that the respective average levels of and B-Y become 0.

In this way, by controlling the gain of the color signal components so that the average level of the color difference signals R-Y and B-Y becomes the value "0" corresponding to "white", the color temperature of the illumination light can be changed. A white subject can always appear white regardless of changes.

As a result of this circuit operation, when the color difference signals R-Y and B-Y with an average level of 0 are input to the modulator 27 (white balance is achieved), the color temperature of the external light changes. , whereby the narrowband luminance signal YL,
When the levels of the primary color signals R and B change, the subtracter 25
and color difference signals R-Y and B output from 26, respectively.
-The average level of Y also deviates from the white balanced value. However, each average level of the color difference signals R-Y and B-Y is input to the white balance microcomputer 31. For this reason, the white balance microcomputer 31 detects that the averaging circuit 3 has reached a level where the white balance has deteriorated.
In order to return the 0 output to a white balanced level again, a digital signal indicating a control voltage of a different magnitude than before is output. As a result, the R gain control circuit 23 and the B gain control circuit 24 output the color difference signal R-Y whose average level is 0 from the subtracter 25 again at the color temperature after the change, and the subtracter 26 outputs the color difference signal RY whose average level is 0 again. The gains of the primary color signals R and B are recontrolled so that a color difference signal B-Y with a level of 0 is output.

In other words, the white balance microcomputer 31 always monitors the average level of the color difference signals R-Y and B-Y output from the subtracters 25 and 26, respectively, and sends them to the R gain control circuit 23 and the B gain control circuit 24. The respective voltages of the control signals GR and GB that are applied are changed to follow the change in color temperature of external light. As a result, the modulator 27 always receives color difference signals R-Y and B-Y whose average level is 0.
is given. Therefore, the composite color video signal output from adder 28 always provides a white balanced image.

In addition, in response to a switch input to an external switch (not shown) called a white balance lock switch, the white balance microcomputer 31 fixes the digital signal output after this switch input to the one at the time of the switch input. It may also have a function. In this case, the digital signal output from the white balance microcomputer 31 does not change following the change in the color temperature of the external light after this switch is input. That is, according to this function, the gain control for the primary color signals R and B is locked to one that matches the color temperature of the external light at the time of this switch input. Such a function is effective when capturing an image of a subject under a color temperature range in which the human eye cannot achieve white balance.

In addition, in such a conventional video camera, the white balance microcomputer 31 generally operates quickly when the power is turned on to the video camera (when imaging starts) and to balance the color temperature over a wide range.

In order to display a white object as white even when the color temperature of the illumination light is varied over a wide range, the average level of each of the color difference signals R-Y and B-Y input to the modulator 27 must be set to a value that deviates significantly from 0. The R gain control circuit 23 and the B gain control circuit are configured so that even if the primary color signals R and B are outputted from the chroma signal processing circuit 22, the average level of each of the color difference signals R-Y and B-Y becomes approximately O. 24 needs to be controlled. Therefore, in the conventional video camera, the white balance microcomputer 31 determines the difference between the average level of each of the color difference signals R-Y and B-Y detected by the averaging circuit 30 and the level at which it can be determined that white balance is achieved. within a relatively wide predetermined range,
As described above, a digital control signal that changes in accordance with changes in color temperature is output. Thereby, the gains of the primary color signals R and B are controlled so that the average level detected by the averaging circuit 13 is approximately 0 over a wide color temperature range. In this way, the white balance microcomputer 31 performs white balance adjustment in a wide color temperature range when the power is turned on. As a result, at the start of normal photographing, the average levels of the color difference signals R-Y and B-Y are once forced to a level that achieves white balance under the color temperature of the external light at the time the power is turned on.

However, if white balance is performed under too wide a range of color temperatures during normal photography, colors that are not even recognized as white by the human eye may appear white due to changes in the color temperature of the subject. In other words, the white balance may shift. Therefore, once the white balance adjustment at power-on is completed, subsequent white balance adjustments are performed in a narrower color temperature range than at power-on. That is, when such white balance adjustment at the time of power-on is completed, the white balance microcomputer 31 thereafter adjusts the white balance to the average level of each of the color difference signals R-Y and B-Y detected by the averaging circuit 30. The average level detected by the averaging circuit 30 is set to approximately 0 when the difference from the level is within a range narrower than the white balance adjustment range (the predetermined relatively wide range) at the time of power-on. , is operative to control the gain of the primary color signals R and B. As a result, during normal shooting, the digital control signal output from the white balance microcomputer 31 changes to follow the change in the color temperature of the external light based on the color temperature of the external light when the power is turned on, and adjusts the white balance. is carried out appropriately.

[Problems to be Solved by the Invention] Many imaging devices have a zoom function that images a distant object as if it were nearby by enlarging the object optically or electrically.

Conventionally, the zoom magnification of consumer imaging devices has generally been about 6x. However, recently, imaging devices capable of capturing images at a zoom magnification of 10 times or 12 times, and even imaging devices capable of capturing images at a zoom magnification of 16 times, have been commercialized. The larger the zoom magnification is, the larger the magnification factor of the subject in the captured image is. Therefore, the larger the zoom magnification is, the smaller the subject range that is enlarged and displayed within the image capture screen. In other words, in an image captured at a high zoom magnification as described above, only a small portion of the subject is enlarged. Therefore, the higher the zoom magnification during imaging, the larger the area occupied by a single color in the captured image often becomes.

On the other hand, in conventional imaging devices having a white balance function, white balance processing is performed when the power is turned on so that the average level of each of the color difference signals R-Y and B-Y becomes 0 over a wide color temperature range. The gain of the color signal component is controlled. Normally, one captured image is composed of many colors, so through white balance processing, the color difference signals of these many colors are averaged together, and the average value of the color difference signal voltage for one screen becomes 0. The gain of the color signal component is controlled so that. However, when the captured image is composed of a single color, there are not many colors in the captured image that can be averaged together, so the color appears whitish than it actually is ( fading phenomenon).

This phenomenon will be explained in more detail.

When the color difference signals R-Y and B-Y are both 0, the color displayed is white. Therefore, in the case described above, the fact that the average value of the color difference signal voltage becomes almost 0 due to white balance processing means that the average level of the color difference signal of one color is forced to almost 0, that is, the captured image This means that the color becomes whitish overall. In other words, according to the conventional color imaging device, the overall color of the captured image becomes whitish due to white balance processing. The degree of such color fading becomes more noticeable as white balance adjustment is performed on a color signal having an average level that deviates significantly from 0.

Therefore, color fading is likely to occur when the power is turned on, when white balance adjustment is performed over a wide color temperature range. In addition, such problems become noticeable in the case of imaging devices having a high zoom magnification, such as those that have been commercialized recently. For example, if you turn on the power with a high zoom magnification in order to capture an image of a human face at a high zoom magnification, the skin tone of the human face will be displayed in a more faded color than it actually is when the power is turned on.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color imaging device that solves the above problems and can display good colors when the power is turned on even when a single color occupies a large area on the imaging screen.

[Means for Solving the Problems] In order to achieve the above objects, the color imaging device according to the present invention includes a lens means for taking in external light, and a color imaging device that responds to the external light taken in by the lens means. a color signal creation means for creating a color signal; a white balance adjustment means for performing white balance adjustment on the color signal created by the color signal creation means; a white plate having a property of diffusing and reflecting light;
A white plate driving means for driving the white plate is provided. The white plate driving means installs the white plate in front of the lens means in response to power-on, and moves the white plate in front of the lens means in response to completion of white balance adjustment by the white balance adjustment means at power-on. Remove more.

[Function] Since the color imaging device according to the present invention is configured as described above, the front surface of the lens means is automatically covered with a white plate when the power is turned on, and at this time, light taken in from the outside is blocked by the white plate. It is diffusely reflected and enters the lens means. therefore,
When the power is turned on, white balance adjustment is performed on the color signals obtained by imaging the white plate. When this white balance adjustment is completed, the white plate is removed from the front surface of the lens means, and light directly enters the lens means from the outside. As a result, white balance adjustment is subsequently performed on the color signal obtained by imaging an external object.

Embodiment FIG. 1 is a schematic block diagram showing the configuration of a color video camera according to an embodiment of the present invention.

Referring to FIG. 1, this video camera, unlike the conventional video camera shown in FIG. 5, includes a white slide cap 1 for momentarily covering the front surface of the lens system 19 when the power is turned on. Furthermore, this video camera includes a white balance adjustment circuit 68 having a configuration different from conventional ones. In addition,
In this video camera, lens system 19. Image sensor 2
0. Luminance signal processing circuit 21. Chroma signal processing circuit 22.
R gain control circuit 23. B gain control circuit 24. Subtractor 25
and 26. Modulator 27. Adder 28. and synchronization signal generator 29 operate in the same manner as in the video camera shown in FIG. The configuration and operation of the white balance adjustment circuit 18 and white slide cap 1 of this video camera will be described in detail below.

Similar to the conventional one, the white balance adjustment circuit 18 includes an averaging circuit 13 that detects each average level of the color difference signals 11-Y and B-Y created by the subtracters 25 and 26, and an averaging circuit 13. A white balance microcomputer 1-4 outputs a control voltage to be applied to the R gain control circuit 23 and the B gain control circuit 24 as a digital signal based on the average 1 novel detected by the white balance microcomputer 14; and a D/A converter 15 that converts the signal into an analog voltage.

The analog voltage converted by the D/A converter 15 is
The control signals GR and GB are applied to the R gain control circuit 23 and the B gain control circuit 24. However, this white balance adjustment circuit 18 further includes a slide gap drive circuit 1 that drives the white slide cap 1.
Contains 7.

The slide cap drive circuit 17 is coupled to the power switch 16 and the white balance microcomputers 1 and 4. The power switch 16 is a power switch for this video camera. The slide cap drive circuits 1 and 7 respond to the switching of the power switch 16 from the OFF state to the ON state, so that the front surface of the lens system 19 changes to the white slide cap 1.
The white slide cap 1 is momentarily moved to the front of the lens system 19 so that it is covered by -. That is, when the video camera is powered on, the white slide cap 1 is placed in front of the lens system 19.

2 to 4 are diagrams showing the structure, mounting position, etc. of the white slide cap 1. FIG. 2 is a perspective view of this video camera with the white slide cap 1 being moved to the front of the lens system 1.9. FIG. 3 shows the lens system 19 and image sensor 2 of this video camera.
FIG. Figure 3(a) is a side view of the cylindrical cabinet, and Figure 3(b) is a side view of the cylindrical cabinet.
) is a view of the cylindrical cabinet viewed from directly above. FIG. 4 is a diagram of the white slide cap 1 viewed from the lens system 19 side.

Referring to FIG. 2, the white slide cap 1 is composed of two white plates 1a and 1b. The white plates 1a and 1b are separately provided on the left and right sides of the front surface of the cylindrical cabinet 3 in which the lens system 19 is built. When the power is turned on, the white plates 1a and ]b are each slid in the direction of the arrow in the figure to completely cover the front surface of the lens system 19.

Referring to FIG. 3(a), the white slide cap 1 is
It is fitted into a groove 30 provided inside the front surface of the cabinet 3. As shown in FIG. 3(b), one gear 2 is provided corresponding to each of the white plates 1a and 1b constituting the white slide cap 1. gear 2
is placed in contact with the corresponding white plate. Both gears 2 are attached to a motor 4 as shown in FIG. 3(a).

In FIG. 1, the white slide cap 1 is shown to be directly driven by the slide cap drive circuit 17, but FIG. 1 conceptually shows the coupling relationship between the white slide cap 1 and the slide cap drive circuit 17. In reality, the motor 4 is connected to the slide cap drive circuit 17.
driven by.

Now, the white plates [a] and 1b constituting the white slide cap 1 have grooves cut into the parts that come into contact with the gear 2 so as to mesh with the gear (see FIG. 4). therefore,
When the motor 4 rotates, the white plate 1 changes according to the rotation of the gear 2.
a and 1b slide along the groove 30.

Here, the white slide cap 1 is made of a white substance having the property of diffusing and reflecting light, such as white polycarbonate resin.

For this reason, referring to FIG. 3(a), when the white slide cap 1 closes the front surface of the cabinet 3 when the power is turned on, the light that has entered the cabinet 3 until the front surface of the cabinet 3 is completely closed is White slide cap]
- is diffusely reflected by the surface on the lens system 19 side. Therefore, when the cabinet 3 is closed by the white slide cap 1, light taken in from the outside and diffusely reflected by the white slide cap 1 enters the 1-noise system 19 inside the cabinet 3. The image sensor 20 converts this light captured by the lens system 19 into an electrical signal. That is, the image sensor 20 images the white slide cap 1 under external light when the power is turned on.

On the other hand, in Figure 1, 1. White balance microcomputer 1
-4. operates as in the conventional video camera shown in FIG. That is, when the power is turned on, the white balance microcomputer 14 quickly controls the gains of the primary color signals R and B so that the average level of each of the color difference signals R-Y and B-Y becomes 0 over a relatively wide color temperature range. Do the action. Therefore, if the image sensor 20 captures an image of the white slide cap illuminated by external light when the power is turned on, the white balance microcomputer 14 adjusts the gains of the primary color signals R and B to be white at the color temperature of the external light when the power is turned on. Control is performed to obtain color difference signals RY and BY that can display an object in white.

Next, the white balance microcomputer 14 adjusts the averaging circuit 1 as a result of the white balance adjustment when the power is turned on.
It is detected that the average level detected by 3 becomes 0. Furthermore, in response to this "detection", the white balance microcomputer 14 controls the slide cap drive circuit 17.
, white slide cap 1. Outputs a control signal to open and return to the original position.

Specifically, the white balance microcomputer 14 outputs a signal to control the slide cap drive circuit 17 so that the slide cap drive circuit 17 rotates the motor 4 shown in FIG. 3 in the opposite direction to that when the power is turned on. by this,
In FIG. 2, the white plates 1a and 1b slide left and right, respectively, and the interruption between the lens system 19 and external light is released.

After the white slide cap 1 is opened by the white balance microcomputer 14, the subject image captured by the lens 19 is displayed on a monitor screen (not shown) or recorded as a video signal on a magnetic tape (not shown). or

Thereafter, the white balance microcomputer 14 controls the gains of the primary color signals R and B so that the average level of each of the color difference signals R-Y and B-Y becomes 0 in a relatively narrow color temperature range, as in the conventional case. Perform the action. in this way,
In this embodiment, when the power is turned on, a white object is first imaged under the color temperature of external light. Therefore, at the start of photography, white balance adjustment is first performed based on the video signal obtained by imaging a white subject so as to match the color temperature of the external light when the power is turned on. Therefore, during subsequent normal shooting, the outputs of the R gain control circuit 23 and the B gain control circuit 24 are created from the gain-adjusted outputs of the R gain control circuit 23 and the B gain control circuit 24 so that a white subject appears white under the color temperature of the external light when the power is turned on. White balance adjustment is performed based on color difference signals. In other words, the first image displayed is
White balance adjustment is always performed based on the video signal of the white object, that is, the white slide cap, rather than the video signal of the object that should originally be imaged. Therefore, even if the power is turned on with the zoom magnification set high, the phenomenon in which the captured image fades due to the white balance adjustment when the power is turned on can be avoided.

In this embodiment, the white cap for white balance adjustment when the power is turned on is composed of two white plates that slide left and right, but the structure of the white cap is not limited to this. For example, the white cap may be composed of two white plates that slide vertically, or may be composed of one white plate that slides vertically or horizontally. Further, the material of the white cap is not limited to polycarbonate resin, and any white substance that has the property of diffusing and reflecting light may be used.

[Effects of the Invention] As described above, according to the present invention, the white balance adjustment when the power is turned on is always performed based on the video signal obtained by imaging a white subject. Therefore, even when a single color occupies a large area on the imaging screen, for example when capturing a part of the subject at a high zoom magnification, the color image quality can be improved without causing discoloration in the captured image when the power is turned on. It becomes possible to provide a good image.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the configuration of a color video camera according to an embodiment of the present invention, FIG. 2 is a perspective view of the color video camera according to the embodiment, and FIG. 3 is a cylindrical portion of the color video camera according to the embodiment. FIG. 4 is a sectional view showing the structure of the white slide cap in FIG. 5, and FIG. 5 is a schematic block diagram showing the structure of a conventional color video camera. In the figure, 1 is a white slide cap, 13 and 3
0 is an averaging circuit, ]4 and 31 are white balance microcontrollers, 15 and 32 are D/A converters, 16 is a power switch, 17 is a slide cap drive circuit, 18 and 33 are white balance adjustment circuits, and 19 is a lens system ,2
0 is an image sensor, 21 is a luminance signal processing circuit, 22 is a chroma signal processing circuit, 23 is an R gain control circuit, 24 is a B gain control circuit, 25 and 26 are subtracters, 27 is a modulator, 28
is an adder, and 29 is a synchronization signal generator. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A white plate having a property of diffusing and reflecting light, a lens means for taking in external light, and responding to the external light taken in by the lens means,
means for creating a color signal; white balance adjustment means for performing white balance adjustment on the color signal created by the color signal creation means; and in response to power-on, the white plate is installed in front of the lens means. and a white plate driving means for removing the white plate from the front surface of the lens means in response to completion of white balance adjustment by the white balance adjustment means at power-on.